commit 7c32e8f8bc upstream.
Allow to pass sk_lookup programs to PROG_TEST_RUN. User space
provides the full bpf_sk_lookup struct as context. Since the
context includes a socket pointer that can't be exposed
to user space we define that PROG_TEST_RUN returns the cookie
of the selected socket or zero in place of the socket pointer.
We don't support testing programs that select a reuseport socket,
since this would mean running another (unrelated) BPF program
from the sk_lookup test handler.
Signed-off-by: Lorenz Bauer <lmb@cloudflare.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20210303101816.36774-3-lmb@cloudflare.com
Signed-off-by: Tianchen Ding <dtcccc@linux.alibaba.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
commit 44a3918c82 upstream.
With unprivileged eBPF enabled, eIBRS (without retpoline) is vulnerable
to Spectre v2 BHB-based attacks.
When both are enabled, print a warning message and report it in the
'spectre_v2' sysfs vulnerabilities file.
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
[fllinden@amazon.com: backported to 5.10]
Signed-off-by: Frank van der Linden <fllinden@amazon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
commit f45b2974cc upstream.
The arch_prepare_bpf_dispatcher function does not have a prototype, and
yields the following warning when W=1 is enabled for the kernel build.
>> arch/x86/net/bpf_jit_comp.c:2188:5: warning: no previous \
prototype for 'arch_prepare_bpf_dispatcher' [-Wmissing-prototypes]
2188 | int arch_prepare_bpf_dispatcher(void *image, s64 *funcs, \
int num_funcs)
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~
Remove the warning by adding a function declaration to include/linux/bpf.h.
Fixes: 75ccbef636 ("bpf: Introduce BPF dispatcher")
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Björn Töpel <bjorn@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20211117125708.769168-1-bjorn@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
commit 353050be4c upstream.
Commit a23740ec43 ("bpf: Track contents of read-only maps as scalars") is
checking whether maps are read-only both from BPF program side and user space
side, and then, given their content is constant, reading out their data via
map->ops->map_direct_value_addr() which is then subsequently used as known
scalar value for the register, that is, it is marked as __mark_reg_known()
with the read value at verification time. Before a23740ec43, the register
content was marked as an unknown scalar so the verifier could not make any
assumptions about the map content.
The current implementation however is prone to a TOCTOU race, meaning, the
value read as known scalar for the register is not guaranteed to be exactly
the same at a later point when the program is executed, and as such, the
prior made assumptions of the verifier with regards to the program will be
invalid which can cause issues such as OOB access, etc.
While the BPF_F_RDONLY_PROG map flag is always fixed and required to be
specified at map creation time, the map->frozen property is initially set to
false for the map given the map value needs to be populated, e.g. for global
data sections. Once complete, the loader "freezes" the map from user space
such that no subsequent updates/deletes are possible anymore. For the rest
of the lifetime of the map, this freeze one-time trigger cannot be undone
anymore after a successful BPF_MAP_FREEZE cmd return. Meaning, any new BPF_*
cmd calls which would update/delete map entries will be rejected with -EPERM
since map_get_sys_perms() removes the FMODE_CAN_WRITE permission. This also
means that pending update/delete map entries must still complete before this
guarantee is given. This corner case is not an issue for loaders since they
create and prepare such program private map in successive steps.
However, a malicious user is able to trigger this TOCTOU race in two different
ways: i) via userfaultfd, and ii) via batched updates. For i) userfaultfd is
used to expand the competition interval, so that map_update_elem() can modify
the contents of the map after map_freeze() and bpf_prog_load() were executed.
This works, because userfaultfd halts the parallel thread which triggered a
map_update_elem() at the time where we copy key/value from the user buffer and
this already passed the FMODE_CAN_WRITE capability test given at that time the
map was not "frozen". Then, the main thread performs the map_freeze() and
bpf_prog_load(), and once that had completed successfully, the other thread
is woken up to complete the pending map_update_elem() which then changes the
map content. For ii) the idea of the batched update is similar, meaning, when
there are a large number of updates to be processed, it can increase the
competition interval between the two. It is therefore possible in practice to
modify the contents of the map after executing map_freeze() and bpf_prog_load().
One way to fix both i) and ii) at the same time is to expand the use of the
map's map->writecnt. The latter was introduced in fc9702273e ("bpf: Add mmap()
support for BPF_MAP_TYPE_ARRAY") and further refined in 1f6cb19be2 ("bpf:
Prevent re-mmap()'ing BPF map as writable for initially r/o mapping") with
the rationale to make a writable mmap()'ing of a map mutually exclusive with
read-only freezing. The counter indicates writable mmap() mappings and then
prevents/fails the freeze operation. Its semantics can be expanded beyond
just mmap() by generally indicating ongoing write phases. This would essentially
span any parallel regular and batched flavor of update/delete operation and
then also have map_freeze() fail with -EBUSY. For the check_mem_access() in
the verifier we expand upon the bpf_map_is_rdonly() check ensuring that all
last pending writes have completed via bpf_map_write_active() test. Once the
map->frozen is set and bpf_map_write_active() indicates a map->writecnt of 0
only then we are really guaranteed to use the map's data as known constants.
For map->frozen being set and pending writes in process of still being completed
we fall back to marking that register as unknown scalar so we don't end up
making assumptions about it. With this, both TOCTOU reproducers from i) and
ii) are fixed.
Note that the map->writecnt has been converted into a atomic64 in the fix in
order to avoid a double freeze_mutex mutex_{un,}lock() pair when updating
map->writecnt in the various map update/delete BPF_* cmd flavors. Spanning
the freeze_mutex over entire map update/delete operations in syscall side
would not be possible due to then causing everything to be serialized.
Similarly, something like synchronize_rcu() after setting map->frozen to wait
for update/deletes to complete is not possible either since it would also
have to span the user copy which can sleep. On the libbpf side, this won't
break d66562fba1 ("libbpf: Add BPF object skeleton support") as the
anonymous mmap()-ed "map initialization image" is remapped as a BPF map-backed
mmap()-ed memory where for .rodata it's non-writable.
Fixes: a23740ec43 ("bpf: Track contents of read-only maps as scalars")
Reported-by: w1tcher.bupt@gmail.com
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
[fix conflict to call bpf_map_write_active_dec() in err_put block.
fix conflict to insert new functions after find_and_alloc_map().]
Reference: CVE-2021-4001
Signed-off-by: Masami Ichikawa(CIP) <masami.ichikawa@cybertrust.co.jp>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
commit 54713c85f5 upstream.
Lorenzo noticed that the code testing for program type compatibility of
tail call maps is potentially racy in that two threads could encounter a
map with an unset type simultaneously and both return true even though they
are inserting incompatible programs.
The race window is quite small, but artificially enlarging it by adding a
usleep_range() inside the check in bpf_prog_array_compatible() makes it
trivial to trigger from userspace with a program that does, essentially:
map_fd = bpf_create_map(BPF_MAP_TYPE_PROG_ARRAY, 4, 4, 2, 0);
pid = fork();
if (pid) {
key = 0;
value = xdp_fd;
} else {
key = 1;
value = tc_fd;
}
err = bpf_map_update_elem(map_fd, &key, &value, 0);
While the race window is small, it has potentially serious ramifications in
that triggering it would allow a BPF program to tail call to a program of a
different type. So let's get rid of it by protecting the update with a
spinlock. The commit in the Fixes tag is the last commit that touches the
code in question.
v2:
- Use a spinlock instead of an atomic variable and cmpxchg() (Alexei)
v3:
- Put lock and the members it protects into an embedded 'owner' struct (Daniel)
Fixes: 3324b584b6 ("ebpf: misc core cleanup")
Reported-by: Lorenzo Bianconi <lorenzo.bianconi@redhat.com>
Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20211026110019.363464-1-toke@redhat.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
[ Upstream commit 356ed64991 ]
Currently if a function ptr in struct_ops has a return value, its
caller will get a random return value from it, because the return
value of related BPF_PROG_TYPE_STRUCT_OPS prog is just dropped.
So adding a new flag BPF_TRAMP_F_RET_FENTRY_RET to tell bpf trampoline
to save and return the return value of struct_ops prog if ret_size of
the function ptr is greater than 0. Also restricting the flag to be
used alone.
Fixes: 85d33df357 ("bpf: Introduce BPF_MAP_TYPE_STRUCT_OPS")
Signed-off-by: Hou Tao <houtao1@huawei.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Link: https://lore.kernel.org/bpf/20210914023351.3664499-1-houtao1@huawei.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
commit b910eaaaa4 upstream.
Jiri Olsa reported a bug ([1]) in kernel where cgroup local
storage pointer may be NULL in bpf_get_local_storage() helper.
There are two issues uncovered by this bug:
(1). kprobe or tracepoint prog incorrectly sets cgroup local storage
before prog run,
(2). due to change from preempt_disable to migrate_disable,
preemption is possible and percpu storage might be overwritten
by other tasks.
This issue (1) is fixed in [2]. This patch tried to address issue (2).
The following shows how things can go wrong:
task 1: bpf_cgroup_storage_set() for percpu local storage
preemption happens
task 2: bpf_cgroup_storage_set() for percpu local storage
preemption happens
task 1: run bpf program
task 1 will effectively use the percpu local storage setting by task 2
which will be either NULL or incorrect ones.
Instead of just one common local storage per cpu, this patch fixed
the issue by permitting 8 local storages per cpu and each local
storage is identified by a task_struct pointer. This way, we
allow at most 8 nested preemption between bpf_cgroup_storage_set()
and bpf_cgroup_storage_unset(). The percpu local storage slot
is released (calling bpf_cgroup_storage_unset()) by the same task
after bpf program finished running.
bpf_test_run() is also fixed to use the new bpf_cgroup_storage_set()
interface.
The patch is tested on top of [2] with reproducer in [1].
Without this patch, kernel will emit error in 2-3 minutes.
With this patch, after one hour, still no error.
[1] https://lore.kernel.org/bpf/CAKH8qBuXCfUz=w8L+Fj74OaUpbosO29niYwTki7e3Ag044_aww@mail.gmail.com/T
[2] https://lore.kernel.org/bpf/20210309185028.3763817-1-yhs@fb.com
Signed-off-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Roman Gushchin <guro@fb.com>
Link: https://lore.kernel.org/bpf/20210323055146.3334476-1-yhs@fb.com
Cc: <stable@vger.kernel.org> # 5.10.x
Signed-off-by: Stanislav Fomichev <sdf@google.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
commit f263a81451 upstream.
Subprograms are calling map_poke_track(), but on program release there is no
hook to call map_poke_untrack(). However, on program release, the aux memory
(and poke descriptor table) is freed even though we still have a reference to
it in the element list of the map aux data. When we run map_poke_run(), we then
end up accessing free'd memory, triggering KASAN in prog_array_map_poke_run():
[...]
[ 402.824689] BUG: KASAN: use-after-free in prog_array_map_poke_run+0xc2/0x34e
[ 402.824698] Read of size 4 at addr ffff8881905a7940 by task hubble-fgs/4337
[ 402.824705] CPU: 1 PID: 4337 Comm: hubble-fgs Tainted: G I 5.12.0+ #399
[ 402.824715] Call Trace:
[ 402.824719] dump_stack+0x93/0xc2
[ 402.824727] print_address_description.constprop.0+0x1a/0x140
[ 402.824736] ? prog_array_map_poke_run+0xc2/0x34e
[ 402.824740] ? prog_array_map_poke_run+0xc2/0x34e
[ 402.824744] kasan_report.cold+0x7c/0xd8
[ 402.824752] ? prog_array_map_poke_run+0xc2/0x34e
[ 402.824757] prog_array_map_poke_run+0xc2/0x34e
[ 402.824765] bpf_fd_array_map_update_elem+0x124/0x1a0
[...]
The elements concerned are walked as follows:
for (i = 0; i < elem->aux->size_poke_tab; i++) {
poke = &elem->aux->poke_tab[i];
[...]
The access to size_poke_tab is a 4 byte read, verified by checking offsets
in the KASAN dump:
[ 402.825004] The buggy address belongs to the object at ffff8881905a7800
which belongs to the cache kmalloc-1k of size 1024
[ 402.825008] The buggy address is located 320 bytes inside of
1024-byte region [ffff8881905a7800, ffff8881905a7c00)
The pahole output of bpf_prog_aux:
struct bpf_prog_aux {
[...]
/* --- cacheline 5 boundary (320 bytes) --- */
u32 size_poke_tab; /* 320 4 */
[...]
In general, subprograms do not necessarily manage their own data structures.
For example, BTF func_info and linfo are just pointers to the main program
structure. This allows reference counting and cleanup to be done on the latter
which simplifies their management a bit. The aux->poke_tab struct, however,
did not follow this logic. The initial proposed fix for this use-after-free
bug further embedded poke data tracking into the subprogram with proper
reference counting. However, Daniel and Alexei questioned why we were treating
these objects special; I agree, its unnecessary. The fix here removes the per
subprogram poke table allocation and map tracking and instead simply points
the aux->poke_tab pointer at the main programs poke table. This way, map
tracking is simplified to the main program and we do not need to manage them
per subprogram.
This also means, bpf_prog_free_deferred(), which unwinds the program reference
counting and kfrees objects, needs to ensure that we don't try to double free
the poke_tab when free'ing the subprog structures. This is easily solved by
NULL'ing the poke_tab pointer. The second detail is to ensure that per
subprogram JIT logic only does fixups on poke_tab[] entries it owns. To do
this, we add a pointer in the poke structure to point at the subprogram value
so JITs can easily check while walking the poke_tab structure if the current
entry belongs to the current program. The aux pointer is stable and therefore
suitable for such comparison. On the jit_subprogs() error path, we omit
cleaning up the poke->aux field because these are only ever referenced from
the JIT side, but on error we will never make it to the JIT, so its fine to
leave them dangling. Removing these pointers would complicate the error path
for no reason. However, we do need to untrack all poke descriptors from the
main program as otherwise they could race with the freeing of JIT memory from
the subprograms. Lastly, a748c6975d ("bpf: propagate poke descriptors to
subprograms") had an off-by-one on the subprogram instruction index range
check as it was testing 'insn_idx >= subprog_start && insn_idx <= subprog_end'.
However, subprog_end is the next subprogram's start instruction.
Fixes: a748c6975d ("bpf: propagate poke descriptors to subprograms")
Signed-off-by: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Co-developed-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20210707223848.14580-2-john.fastabend@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
[ Upstream commit 01f810ace9 ]
Before this patch, variable offset access to the stack was dissalowed
for regular instructions, but was allowed for "indirect" accesses (i.e.
helpers). This patch removes the restriction, allowing reading and
writing to the stack through stack pointers with variable offsets. This
makes stack-allocated buffers more usable in programs, and brings stack
pointers closer to other types of pointers.
The motivation is being able to use stack-allocated buffers for data
manipulation. When the stack size limit is sufficient, allocating
buffers on the stack is simpler than per-cpu arrays, or other
alternatives.
In unpriviledged programs, variable-offset reads and writes are
disallowed (they were already disallowed for the indirect access case)
because the speculative execution checking code doesn't support them.
Additionally, when writing through a variable-offset stack pointer, if
any pointers are in the accessible range, there's possilibities of later
leaking pointers because the write cannot be tracked precisely.
Writes with variable offset mark the whole range as initialized, even
though we don't know which stack slots are actually written. This is in
order to not reject future reads to these slots. Note that this doesn't
affect writes done through helpers; like before, helpers need the whole
stack range to be initialized to begin with.
All the stack slots are in range are considered scalars after the write;
variable-offset register spills are not tracked.
For reads, all the stack slots in the variable range needs to be
initialized (but see above about what writes do), otherwise the read is
rejected. All register spilled in stack slots that might be read are
marked as having been read, however reads through such pointers don't do
register filling; the target register will always be either a scalar or
a constant zero.
Signed-off-by: Andrei Matei <andreimatei1@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20210207011027.676572-2-andreimatei1@gmail.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
[ Upstream commit e21aa34178 ]
The fexit/fmod_ret programs can be attached to kernel functions that can sleep.
The synchronize_rcu_tasks() will not wait for such tasks to complete.
In such case the trampoline image will be freed and when the task
wakes up the return IP will point to freed memory causing the crash.
Solve this by adding percpu_ref_get/put for the duration of trampoline
and separate trampoline vs its image life times.
The "half page" optimization has to be removed, since
first_half->second_half->first_half transition cannot be guaranteed to
complete in deterministic time. Every trampoline update becomes a new image.
The image with fmod_ret or fexit progs will be freed via percpu_ref_kill and
call_rcu_tasks. Together they will wait for the original function and
trampoline asm to complete. The trampoline is patched from nop to jmp to skip
fexit progs. They are freed independently from the trampoline. The image with
fentry progs only will be freed via call_rcu_tasks_trace+call_rcu_tasks which
will wait for both sleepable and non-sleepable progs to complete.
Fixes: fec56f5890 ("bpf: Introduce BPF trampoline")
Reported-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Paul E. McKenney <paulmck@kernel.org> # for RCU
Link: https://lore.kernel.org/bpf/20210316210007.38949-1-alexei.starovoitov@gmail.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
[ Upstream commit 05a68ce5fa ]
For kuprobe and tracepoint bpf programs, kernel calls
trace_call_bpf() which calls BPF_PROG_RUN_ARRAY_CHECK()
to run the program array. Currently, BPF_PROG_RUN_ARRAY_CHECK()
also calls bpf_cgroup_storage_set() to set percpu
cgroup local storage with NULL value. This is
due to Commit 394e40a297 ("bpf: extend bpf_prog_array to store
pointers to the cgroup storage") which modified
__BPF_PROG_RUN_ARRAY() to call bpf_cgroup_storage_set()
and this macro is also used by BPF_PROG_RUN_ARRAY_CHECK().
kuprobe and tracepoint programs are not allowed to call
bpf_get_local_storage() helper hence does not
access percpu cgroup local storage. Let us
change BPF_PROG_RUN_ARRAY_CHECK() not to
modify percpu cgroup local storage.
The issue is observed when I tried to debug [1] where
percpu data is overwritten due to
preempt_disable -> migration_disable
change. This patch does not completely fix the above issue,
which will be addressed separately, e.g., multiple cgroup
prog runs may preempt each other. But it does fix
any potential issue caused by tracing program
overwriting percpu cgroup storage:
- in a busy system, a tracing program is to run between
bpf_cgroup_storage_set() and the cgroup prog run.
- a kprobe program is triggered by a helper in cgroup prog
before bpf_get_local_storage() is called.
[1] https://lore.kernel.org/bpf/CAKH8qBuXCfUz=w8L+Fj74OaUpbosO29niYwTki7e3Ag044_aww@mail.gmail.com/T
Fixes: 394e40a297 ("bpf: extend bpf_prog_array to store pointers to the cgroup storage")
Signed-off-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Roman Gushchin <guro@fb.com>
Link: https://lore.kernel.org/bpf/20210309185028.3763817-1-yhs@fb.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
[ Upstream commit 936f8946bd ]
__bpf_free_used_maps() is always defined in kernel/bpf/core.c, while
include/linux/bpf.h is guarding it behind CONFIG_BPF_SYSCALL. Move it out of
that guard region and fix compiler warning.
Fixes: a2ea07465c ("bpf: Fix missing prog untrack in release_maps")
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20210112075520.4103414-4-andrii@kernel.org
Signed-off-by: Sasha Levin <sashal@kernel.org>
[ Upstream commit a643bff752 ]
Add bpf_patch_call_args() prototype. This function is called from BPF verifier
and only if CONFIG_BPF_JIT_ALWAYS_ON is not defined. This fixes compiler
warning about missing prototype in some kernel configurations.
Fixes: 1ea47e01ad ("bpf: add support for bpf_call to interpreter")
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20210112075520.4103414-2-andrii@kernel.org
Signed-off-by: Sasha Levin <sashal@kernel.org>
Recent work in f4d0525921 ("bpf: Add map_meta_equal map ops") and 134fede4ee
("bpf: Relax max_entries check for most of the inner map types") added support
for dynamic inner max elements for most map-in-map types. Exceptions were maps
like array or prog array where the map_gen_lookup() callback uses the maps'
max_entries field as a constant when emitting instructions.
We recently implemented Maglev consistent hashing into Cilium's load balancer
which uses map-in-map with an outer map being hash and inner being array holding
the Maglev backend table for each service. This has been designed this way in
order to reduce overall memory consumption given the outer hash map allows to
avoid preallocating a large, flat memory area for all services. Also, the
number of service mappings is not always known a-priori.
The use case for dynamic inner array map entries is to further reduce memory
overhead, for example, some services might just have a small number of back
ends while others could have a large number. Right now the Maglev backend table
for small and large number of backends would need to have the same inner array
map entries which adds a lot of unneeded overhead.
Dynamic inner array map entries can be realized by avoiding the inlined code
generation for their lookup. The lookup will still be efficient since it will
be calling into array_map_lookup_elem() directly and thus avoiding retpoline.
The patch adds a BPF_F_INNER_MAP flag to map creation which therefore skips
inline code generation and relaxes array_map_meta_equal() check to ignore both
maps' max_entries. This also still allows to have faster lookups for map-in-map
when BPF_F_INNER_MAP is not specified and hence dynamic max_entries not needed.
Example code generation where inner map is dynamic sized array:
# bpftool p d x i 125
int handle__sys_enter(void * ctx):
; int handle__sys_enter(void *ctx)
0: (b4) w1 = 0
; int key = 0;
1: (63) *(u32 *)(r10 -4) = r1
2: (bf) r2 = r10
;
3: (07) r2 += -4
; inner_map = bpf_map_lookup_elem(&outer_arr_dyn, &key);
4: (18) r1 = map[id:468]
6: (07) r1 += 272
7: (61) r0 = *(u32 *)(r2 +0)
8: (35) if r0 >= 0x3 goto pc+5
9: (67) r0 <<= 3
10: (0f) r0 += r1
11: (79) r0 = *(u64 *)(r0 +0)
12: (15) if r0 == 0x0 goto pc+1
13: (05) goto pc+1
14: (b7) r0 = 0
15: (b4) w6 = -1
; if (!inner_map)
16: (15) if r0 == 0x0 goto pc+6
17: (bf) r2 = r10
;
18: (07) r2 += -4
; val = bpf_map_lookup_elem(inner_map, &key);
19: (bf) r1 = r0 | No inlining but instead
20: (85) call array_map_lookup_elem#149280 | call to array_map_lookup_elem()
; return val ? *val : -1; | for inner array lookup.
21: (15) if r0 == 0x0 goto pc+1
; return val ? *val : -1;
22: (61) r6 = *(u32 *)(r0 +0)
; }
23: (bc) w0 = w6
24: (95) exit
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20201010234006.7075-4-daniel@iogearbox.net
Add bpf_this_cpu_ptr() to help access percpu var on this cpu. This
helper always returns a valid pointer, therefore no need to check
returned value for NULL. Also note that all programs run with
preemption disabled, which means that the returned pointer is stable
during all the execution of the program.
Signed-off-by: Hao Luo <haoluo@google.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Link: https://lore.kernel.org/bpf/20200929235049.2533242-6-haoluo@google.com
Add bpf_per_cpu_ptr() to help bpf programs access percpu vars.
bpf_per_cpu_ptr() has the same semantic as per_cpu_ptr() in the kernel
except that it may return NULL. This happens when the cpu parameter is
out of range. So the caller must check the returned value.
Signed-off-by: Hao Luo <haoluo@google.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Link: https://lore.kernel.org/bpf/20200929235049.2533242-5-haoluo@google.com
This enables support for attaching freplace programs to multiple attach
points. It does this by amending the UAPI for bpf_link_Create with a target
btf ID that can be used to supply the new attachment point along with the
target program fd. The target must be compatible with the target that was
supplied at program load time.
The implementation reuses the checks that were factored out of
check_attach_btf_id() to ensure compatibility between the BTF types of the
old and new attachment. If these match, a new bpf_tracing_link will be
created for the new attach target, allowing multiple attachments to
co-exist simultaneously.
The code could theoretically support multiple-attach of other types of
tracing programs as well, but since I don't have a use case for any of
those, there is no API support for doing so.
Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Link: https://lore.kernel.org/bpf/160138355169.48470.17165680973640685368.stgit@toke.dk
In preparation for allowing multiple attachments of freplace programs, move
the references to the target program and trampoline into the
bpf_tracing_link structure when that is created. To do this atomically,
introduce a new mutex in prog->aux to protect writing to the two pointers
to target prog and trampoline, and rename the members to make it clear that
they are related.
With this change, it is no longer possible to attach the same tracing
program multiple times (detaching in-between), since the reference from the
tracing program to the target disappears on the first attach. However,
since the next patch will let the caller supply an attach target, that will
also make it possible to attach to the same place multiple times.
Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Link: https://lore.kernel.org/bpf/160138355059.48470.2503076992210324984.stgit@toke.dk
A helper is added to support tracing kernel type information in BPF
using the BPF Type Format (BTF). Its signature is
long bpf_snprintf_btf(char *str, u32 str_size, struct btf_ptr *ptr,
u32 btf_ptr_size, u64 flags);
struct btf_ptr * specifies
- a pointer to the data to be traced
- the BTF id of the type of data pointed to
- a flags field is provided for future use; these flags
are not to be confused with the BTF_F_* flags
below that control how the btf_ptr is displayed; the
flags member of the struct btf_ptr may be used to
disambiguate types in kernel versus module BTF, etc;
the main distinction is the flags relate to the type
and information needed in identifying it; not how it
is displayed.
For example a BPF program with a struct sk_buff *skb
could do the following:
static struct btf_ptr b = { };
b.ptr = skb;
b.type_id = __builtin_btf_type_id(struct sk_buff, 1);
bpf_snprintf_btf(str, sizeof(str), &b, sizeof(b), 0, 0);
Default output looks like this:
(struct sk_buff){
.transport_header = (__u16)65535,
.mac_header = (__u16)65535,
.end = (sk_buff_data_t)192,
.head = (unsigned char *)0x000000007524fd8b,
.data = (unsigned char *)0x000000007524fd8b,
.truesize = (unsigned int)768,
.users = (refcount_t){
.refs = (atomic_t){
.counter = (int)1,
},
},
}
Flags modifying display are as follows:
- BTF_F_COMPACT: no formatting around type information
- BTF_F_NONAME: no struct/union member names/types
- BTF_F_PTR_RAW: show raw (unobfuscated) pointer values;
equivalent to %px.
- BTF_F_ZERO: show zero-valued struct/union members;
they are not displayed by default
Signed-off-by: Alan Maguire <alan.maguire@oracle.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/1601292670-1616-4-git-send-email-alan.maguire@oracle.com
The check_attach_btf_id() function really does three things:
1. It performs a bunch of checks on the program to ensure that the
attachment is valid.
2. It stores a bunch of state about the attachment being requested in
the verifier environment and struct bpf_prog objects.
3. It allocates a trampoline for the attachment.
This patch splits out (1.) and (3.) into separate functions which will
perform the checks, but return the computed values instead of directly
modifying the environment. This is done in preparation for reusing the
checks when the actual attachment is happening, which will allow tracing
programs to have multiple (compatible) attachments.
This also fixes a bug where a bunch of checks were skipped if a trampoline
already existed for the tracing target.
Fixes: 6ba43b761c ("bpf: Attachment verification for BPF_MODIFY_RETURN")
Fixes: 1e6c62a882 ("bpf: Introduce sleepable BPF programs")
Acked-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
In preparation for moving code around, change a bunch of references to
env->log (and the verbose() logging helper) to use bpf_log() and a direct
pointer to struct bpf_verifier_log. While we're touching the function
signature, mark the 'prog' argument to bpf_check_type_match() as const.
Also enhance the bpf_verifier_log_needed() check to handle NULL pointers
for the log struct so we can re-use the code with logging disabled.
Acked-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Add .test_run for raw_tracepoint. Also, introduce a new feature that runs
the target program on a specific CPU. This is achieved by a new flag in
bpf_attr.test, BPF_F_TEST_RUN_ON_CPU. When this flag is set, the program
is triggered on cpu with id bpf_attr.test.cpu. This feature is needed for
BPF programs that handle perf_event and other percpu resources, as the
program can access these resource locally.
Signed-off-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Link: https://lore.kernel.org/bpf/20200925205432.1777-2-songliubraving@fb.com
The meaning of PTR_TO_BTF_ID_OR_NULL differs slightly from other types
denoted with the *_OR_NULL type. For example the types PTR_TO_SOCKET
and PTR_TO_SOCKET_OR_NULL can be used for branch analysis because the
type PTR_TO_SOCKET is guaranteed to _not_ have a null value.
In contrast PTR_TO_BTF_ID and BTF_TO_BTF_ID_OR_NULL have slightly
different meanings. A PTR_TO_BTF_TO_ID may be a pointer to NULL value,
but it is safe to read this pointer in the program context because
the program context will handle any faults. The fallout is for
PTR_TO_BTF_ID the verifier can assume reads are safe, but can not
use the type in branch analysis. Additionally, authors need to be
extra careful when passing PTR_TO_BTF_ID into helpers. In general
helpers consuming type PTR_TO_BTF_ID will need to assume it may
be null.
Seeing the above is not obvious to readers without the back knowledge
lets add a comment in the type definition.
Editorial comment, as networking and tracing programs get closer
and more tightly merged we may need to consider a new type that we
can ensure is non-null for branch analysis and also passing into
helpers.
Signed-off-by: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Lorenz Bauer <lmb@cloudflare.com>
There is a constant need to add more fields into the bpf_tcp_sock
for the bpf programs running at tc, sock_ops...etc.
A current workaround could be to use bpf_probe_read_kernel(). However,
other than making another helper call for reading each field and missing
CO-RE, it is also not as intuitive to use as directly reading
"tp->lsndtime" for example. While already having perfmon cap to do
bpf_probe_read_kernel(), it will be much easier if the bpf prog can
directly read from the tcp_sock.
This patch tries to do that by using the existing casting-helpers
bpf_skc_to_*() whose func_proto returns a btf_id. For example, the
func_proto of bpf_skc_to_tcp_sock returns the btf_id of the
kernel "struct tcp_sock".
These helpers are also added to is_ptr_cast_function().
It ensures the returning reg (BPF_REF_0) will also carries the ref_obj_id.
That will keep the ref-tracking works properly.
The bpf_skc_to_* helpers are made available to most of the bpf prog
types in filter.c. The bpf_skc_to_* helpers will be limited by
perfmon cap.
This patch adds a ARG_PTR_TO_BTF_ID_SOCK_COMMON. The helper accepting
this arg can accept a btf-id-ptr (PTR_TO_BTF_ID + &btf_sock_ids[BTF_SOCK_TYPE_SOCK_COMMON])
or a legacy-ctx-convert-skc-ptr (PTR_TO_SOCK_COMMON). The bpf_skc_to_*()
helpers are changed to take ARG_PTR_TO_BTF_ID_SOCK_COMMON such that
they will accept pointer obtained from skb->sk.
Instead of specifying both arg_type and arg_btf_id in the same func_proto
which is how the current ARG_PTR_TO_BTF_ID does, the arg_btf_id of
the new ARG_PTR_TO_BTF_ID_SOCK_COMMON is specified in the
compatible_reg_types[] in verifier.c. The reason is the arg_btf_id is
always the same. Discussion in this thread:
https://lore.kernel.org/bpf/20200922070422.1917351-1-kafai@fb.com/
The ARG_PTR_TO_BTF_ID_ part gives a clear expectation that the helper is
expecting a PTR_TO_BTF_ID which could be NULL. This is the same
behavior as the existing helper taking ARG_PTR_TO_BTF_ID.
The _SOCK_COMMON part means the helper is also expecting the legacy
SOCK_COMMON pointer.
By excluding the _OR_NULL part, the bpf prog cannot call helper
with a literal NULL which doesn't make sense in most cases.
e.g. bpf_skc_to_tcp_sock(NULL) will be rejected. All PTR_TO_*_OR_NULL
reg has to do a NULL check first before passing into the helper or else
the bpf prog will be rejected. This behavior is nothing new and
consistent with the current expectation during bpf-prog-load.
[ ARG_PTR_TO_BTF_ID_SOCK_COMMON will be used to replace
ARG_PTR_TO_SOCK* of other existing helpers later such that
those existing helpers can take the PTR_TO_BTF_ID returned by
the bpf_skc_to_*() helpers.
The only special case is bpf_sk_lookup_assign() which can accept a
literal NULL ptr. It has to be handled specially in another follow
up patch if there is a need (e.g. by renaming ARG_PTR_TO_SOCKET_OR_NULL
to ARG_PTR_TO_BTF_ID_SOCK_COMMON_OR_NULL). ]
[ When converting the older helpers that take ARG_PTR_TO_SOCK* in
the later patch, if the kernel does not support BTF,
ARG_PTR_TO_BTF_ID_SOCK_COMMON will behave like ARG_PTR_TO_SOCK_COMMON
because no reg->type could have PTR_TO_BTF_ID in this case.
It is not a concern for the newer-btf-only helper like the bpf_skc_to_*()
here though because these helpers must require BTF vmlinux to begin
with. ]
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Link: https://lore.kernel.org/bpf/20200925000350.3855720-1-kafai@fb.com
The mapping between bpf_arg_type and bpf_reg_type is encoded in a big
hairy if statement that is hard to follow. The debug output also leaves
to be desired: if a reg_type doesn't match we only print one of the
options, instead printing all the valid ones.
Convert the if statement into a table which is then used to drive type
checking. If none of the reg_types match we print all options, e.g.:
R2 type=rdonly_buf expected=fp, pkt, pkt_meta, map_value
Signed-off-by: Lorenz Bauer <lmb@cloudflare.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Link: https://lore.kernel.org/bpf/20200921121227.255763-12-lmb@cloudflare.com
Function prototypes using ARG_PTR_TO_BTF_ID currently use two ways to signal
which BTF IDs are acceptable. First, bpf_func_proto.btf_id is an array of
IDs, one for each argument. This array is only accessed up to the highest
numbered argument that uses ARG_PTR_TO_BTF_ID and may therefore be less than
five arguments long. It usually points at a BTF_ID_LIST. Second, check_btf_id
is a function pointer that is called by the verifier if present. It gets the
actual BTF ID of the register, and the argument number we're currently checking.
It turns out that the only user check_arg_btf_id ignores the argument, and is
simply used to check whether the BTF ID has a struct sock_common at it's start.
Replace both of these mechanisms with an explicit BTF ID for each argument
in a function proto. Thanks to btf_struct_ids_match this is very flexible:
check_arg_btf_id can be replaced by requiring struct sock_common.
Signed-off-by: Lorenz Bauer <lmb@cloudflare.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Link: https://lore.kernel.org/bpf/20200921121227.255763-5-lmb@cloudflare.com
bsearch doesn't modify the contents of the array, so we can take a const pointer.
Signed-off-by: Lorenz Bauer <lmb@cloudflare.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Link: https://lore.kernel.org/bpf/20200921121227.255763-2-lmb@cloudflare.com
This commit serves two things:
1) it optimizes BPF prologue/epilogue generation
2) it makes possible to have tailcalls within BPF subprogram
Both points are related to each other since without 1), 2) could not be
achieved.
In [1], Alexei says:
"The prologue will look like:
nop5
xor eax,eax // two new bytes if bpf_tail_call() is used in this
// function
push rbp
mov rbp, rsp
sub rsp, rounded_stack_depth
push rax // zero init tail_call counter
variable number of push rbx,r13,r14,r15
Then bpf_tail_call will pop variable number rbx,..
and final 'pop rax'
Then 'add rsp, size_of_current_stack_frame'
jmp to next function and skip over 'nop5; xor eax,eax; push rpb; mov
rbp, rsp'
This way new function will set its own stack size and will init tail
call
counter with whatever value the parent had.
If next function doesn't use bpf_tail_call it won't have 'xor eax,eax'.
Instead it would need to have 'nop2' in there."
Implement that suggestion.
Since the layout of stack is changed, tail call counter handling can not
rely anymore on popping it to rbx just like it have been handled for
constant prologue case and later overwrite of rbx with actual value of
rbx pushed to stack. Therefore, let's use one of the register (%rcx) that
is considered to be volatile/caller-saved and pop the value of tail call
counter in there in the epilogue.
Drop the BUILD_BUG_ON in emit_prologue and in
emit_bpf_tail_call_indirect where instruction layout is not constant
anymore.
Introduce new poke target, 'tailcall_bypass' to poke descriptor that is
dedicated for skipping the register pops and stack unwind that are
generated right before the actual jump to target program.
For case when the target program is not present, BPF program will skip
the pop instructions and nop5 dedicated for jmpq $target. An example of
such state when only R6 of callee saved registers is used by program:
ffffffffc0513aa1: e9 0e 00 00 00 jmpq 0xffffffffc0513ab4
ffffffffc0513aa6: 5b pop %rbx
ffffffffc0513aa7: 58 pop %rax
ffffffffc0513aa8: 48 81 c4 00 00 00 00 add $0x0,%rsp
ffffffffc0513aaf: 0f 1f 44 00 00 nopl 0x0(%rax,%rax,1)
ffffffffc0513ab4: 48 89 df mov %rbx,%rdi
When target program is inserted, the jump that was there to skip
pops/nop5 will become the nop5, so CPU will go over pops and do the
actual tailcall.
One might ask why there simply can not be pushes after the nop5?
In the following example snippet:
ffffffffc037030c: 48 89 fb mov %rdi,%rbx
(...)
ffffffffc0370332: 5b pop %rbx
ffffffffc0370333: 58 pop %rax
ffffffffc0370334: 48 81 c4 00 00 00 00 add $0x0,%rsp
ffffffffc037033b: 0f 1f 44 00 00 nopl 0x0(%rax,%rax,1)
ffffffffc0370340: 48 81 ec 00 00 00 00 sub $0x0,%rsp
ffffffffc0370347: 50 push %rax
ffffffffc0370348: 53 push %rbx
ffffffffc0370349: 48 89 df mov %rbx,%rdi
ffffffffc037034c: e8 f7 21 00 00 callq 0xffffffffc0372548
There is the bpf2bpf call (at ffffffffc037034c) right after the tailcall
and jump target is not present. ctx is in %rbx register and BPF
subprogram that we will call into on ffffffffc037034c is relying on it,
e.g. it will pick ctx from there. Such code layout is therefore broken
as we would overwrite the content of %rbx with the value that was pushed
on the prologue. That is the reason for the 'bypass' approach.
Special care needs to be taken during the install/update/remove of
tailcall target. In case when target program is not present, the CPU
must not execute the pop instructions that precede the tailcall.
To address that, the following states can be defined:
A nop, unwind, nop
B nop, unwind, tail
C skip, unwind, nop
D skip, unwind, tail
A is forbidden (lead to incorrectness). The state transitions between
tailcall install/update/remove will work as follows:
First install tail call f: C->D->B(f)
* poke the tailcall, after that get rid of the skip
Update tail call f to f': B(f)->B(f')
* poke the tailcall (poke->tailcall_target) and do NOT touch the
poke->tailcall_bypass
Remove tail call: B(f')->C(f')
* poke->tailcall_bypass is poked back to jump, then we wait the RCU
grace period so that other programs will finish its execution and
after that we are safe to remove the poke->tailcall_target
Install new tail call (f''): C(f')->D(f'')->B(f'').
* same as first step
This way CPU can never be exposed to "unwind, tail" state.
Last but not least, when tailcalls get mixed with bpf2bpf calls, it
would be possible to encounter the endless loop due to clearing the
tailcall counter if for example we would use the tailcall3-like from BPF
selftests program that would be subprogram-based, meaning the tailcall
would be present within the BPF subprogram.
This test, broken down to particular steps, would do:
entry -> set tailcall counter to 0, bump it by 1, tailcall to func0
func0 -> call subprog_tail
(we are NOT skipping the first 11 bytes of prologue and this subprogram
has a tailcall, therefore we clear the counter...)
subprog -> do the same thing as entry
and then loop forever.
To address this, the idea is to go through the call chain of bpf2bpf progs
and look for a tailcall presence throughout whole chain. If we saw a single
tail call then each node in this call chain needs to be marked as a subprog
that can reach the tailcall. We would later feed the JIT with this info
and:
- set eax to 0 only when tailcall is reachable and this is the entry prog
- if tailcall is reachable but there's no tailcall in insns of currently
JITed prog then push rax anyway, so that it will be possible to
propagate further down the call chain
- finally if tailcall is reachable, then we need to precede the 'call'
insn with mov rax, [rbp - (stack_depth + 8)]
Tail call related cases from test_verifier kselftest are also working
fine. Sample BPF programs that utilize tail calls (sockex3, tracex5)
work properly as well.
[1]: https://lore.kernel.org/bpf/20200517043227.2gpq22ifoq37ogst@ast-mbp.dhcp.thefacebook.com/
Suggested-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Reflect the actual purpose of poke->ip and rename it to
poke->tailcall_target so that it will not the be confused with another
poke target that will be introduced in next commit.
While at it, do the same thing with poke->ip_stable - rename it to
poke->tailcall_target_stable.
Signed-off-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Previously, there was no need for poke descriptors being present in
subprogram's bpf_prog_aux struct since tailcalls were simply not allowed
in them. Each subprog is JITed independently so in order to enable
JITing subprograms that use tailcalls, do the following:
- in fixup_bpf_calls() store the index of tailcall insn onto the generated
poke descriptor,
- in case when insn patching occurs, adjust the tailcall insn idx from
bpf_patch_insn_data,
- then in jit_subprogs() check whether the given poke descriptor belongs
to the current subprog by checking if that previously stored absolute
index of tail call insn is in the scope of the insns of given subprog,
- update the insn->imm with new poke descriptor slot so that while JITing
the proper poke descriptor will be grabbed
This way each of the main program's poke descriptors are distributed
across the subprograms poke descriptor array, so main program's
descriptors can be untracked out of the prog array map.
Add also subprog's aux struct to the BPF map poke_progs list by calling
on it map_poke_track().
In case of any error, call the map_poke_untrack() on subprog's aux
structs that have already been registered to prog array map.
Signed-off-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
To support modifying the used_maps array, we use a mutex to protect
the use of the counter and the array. The mutex is initialized right
after the prog aux is allocated, and destroyed right before prog
aux is freed. This way we guarantee it's initialized for both cBPF
and eBPF.
Signed-off-by: YiFei Zhu <zhuyifei@google.com>
Signed-off-by: Stanislav Fomichev <sdf@google.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Cc: YiFei Zhu <zhuyifei1999@gmail.com>
Link: https://lore.kernel.org/bpf/20200915234543.3220146-2-sdf@google.com
Sleepable BPF programs can now use copy_from_user() to access user memory.
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Acked-by: KP Singh <kpsingh@google.com>
Link: https://lore.kernel.org/bpf/20200827220114.69225-4-alexei.starovoitov@gmail.com
Introduce sleepable BPF programs that can request such property for themselves
via BPF_F_SLEEPABLE flag at program load time. In such case they will be able
to use helpers like bpf_copy_from_user() that might sleep. At present only
fentry/fexit/fmod_ret and lsm programs can request to be sleepable and only
when they are attached to kernel functions that are known to allow sleeping.
The non-sleepable programs are relying on implicit rcu_read_lock() and
migrate_disable() to protect life time of programs, maps that they use and
per-cpu kernel structures used to pass info between bpf programs and the
kernel. The sleepable programs cannot be enclosed into rcu_read_lock().
migrate_disable() maps to preempt_disable() in non-RT kernels, so the progs
should not be enclosed in migrate_disable() as well. Therefore
rcu_read_lock_trace is used to protect the life time of sleepable progs.
There are many networking and tracing program types. In many cases the
'struct bpf_prog *' pointer itself is rcu protected within some other kernel
data structure and the kernel code is using rcu_dereference() to load that
program pointer and call BPF_PROG_RUN() on it. All these cases are not touched.
Instead sleepable bpf programs are allowed with bpf trampoline only. The
program pointers are hard-coded into generated assembly of bpf trampoline and
synchronize_rcu_tasks_trace() is used to protect the life time of the program.
The same trampoline can hold both sleepable and non-sleepable progs.
When rcu_read_lock_trace is held it means that some sleepable bpf program is
running from bpf trampoline. Those programs can use bpf arrays and preallocated
hash/lru maps. These map types are waiting on programs to complete via
synchronize_rcu_tasks_trace();
Updates to trampoline now has to do synchronize_rcu_tasks_trace() and
synchronize_rcu_tasks() to wait for sleepable progs to finish and for
trampoline assembly to finish.
This is the first step of introducing sleepable progs. Eventually dynamically
allocated hash maps can be allowed and networking program types can become
sleepable too.
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Acked-by: KP Singh <kpsingh@google.com>
Link: https://lore.kernel.org/bpf/20200827220114.69225-3-alexei.starovoitov@gmail.com
Some properties of the inner map is used in the verification time.
When an inner map is inserted to an outer map at runtime,
bpf_map_meta_equal() is currently used to ensure those properties
of the inserting inner map stays the same as the verification
time.
In particular, the current bpf_map_meta_equal() checks max_entries which
turns out to be too restrictive for most of the maps which do not use
max_entries during the verification time. It limits the use case that
wants to replace a smaller inner map with a larger inner map. There are
some maps do use max_entries during verification though. For example,
the map_gen_lookup in array_map_ops uses the max_entries to generate
the inline lookup code.
To accommodate differences between maps, the map_meta_equal is added
to bpf_map_ops. Each map-type can decide what to check when its
map is used as an inner map during runtime.
Also, some map types cannot be used as an inner map and they are
currently black listed in bpf_map_meta_alloc() in map_in_map.c.
It is not unusual that the new map types may not aware that such
blacklist exists. This patch enforces an explicit opt-in
and only allows a map to be used as an inner map if it has
implemented the map_meta_equal ops. It is based on the
discussion in [1].
All maps that support inner map has its map_meta_equal points
to bpf_map_meta_equal in this patch. A later patch will
relax the max_entries check for most maps. bpf_types.h
counts 28 map types. This patch adds 23 ".map_meta_equal"
by using coccinelle. -5 for
BPF_MAP_TYPE_PROG_ARRAY
BPF_MAP_TYPE_(PERCPU)_CGROUP_STORAGE
BPF_MAP_TYPE_STRUCT_OPS
BPF_MAP_TYPE_ARRAY_OF_MAPS
BPF_MAP_TYPE_HASH_OF_MAPS
The "if (inner_map->inner_map_meta)" check in bpf_map_meta_alloc()
is moved such that the same error is returned.
[1]: https://lore.kernel.org/bpf/20200522022342.899756-1-kafai@fb.com/
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20200828011806.1970400-1-kafai@fb.com
Adding support to define sorted set of BTF ID values.
Following defines sorted set of BTF ID values:
BTF_SET_START(btf_allowlist_d_path)
BTF_ID(func, vfs_truncate)
BTF_ID(func, vfs_fallocate)
BTF_ID(func, dentry_open)
BTF_ID(func, vfs_getattr)
BTF_ID(func, filp_close)
BTF_SET_END(btf_allowlist_d_path)
It defines following 'struct btf_id_set' variable to access
values and count:
struct btf_id_set btf_allowlist_d_path;
Adding 'allowed' callback to struct bpf_func_proto, to allow
verifier the check on allowed callers.
Adding btf_id_set_contains function, which will be used by
allowed callbacks to verify the caller's BTF ID value is
within allowed set.
Also removing extra '\' in __BTF_ID_LIST macro.
Added BTF_SET_START_GLOBAL macro for global sets.
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Link: https://lore.kernel.org/bpf/20200825192124.710397-10-jolsa@kernel.org
Adding btf_struct_ids_match function to check if given address provided
by BTF object + offset is also address of another nested BTF object.
This allows to pass an argument to helper, which is defined via parent
BTF object + offset, like for bpf_d_path (added in following changes):
SEC("fentry/filp_close")
int BPF_PROG(prog_close, struct file *file, void *id)
{
...
ret = bpf_d_path(&file->f_path, ...
The first bpf_d_path argument is hold by verifier as BTF file object
plus offset of f_path member.
The btf_struct_ids_match function will walk the struct file object and
check if there's nested struct path object on the given offset.
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Link: https://lore.kernel.org/bpf/20200825192124.710397-9-jolsa@kernel.org
Refactor the functionality in bpf_sk_storage.c so that concept of
storage linked to kernel objects can be extended to other objects like
inode, task_struct etc.
Each new local storage will still be a separate map and provide its own
set of helpers. This allows for future object specific extensions and
still share a lot of the underlying implementation.
This includes the changes suggested by Martin in:
https://lore.kernel.org/bpf/20200725013047.4006241-1-kafai@fb.com/
adding new map operations to support bpf_local_storage maps:
* storages for different kernel objects to optionally have different
memory charging strategy (map_local_storage_charge,
map_local_storage_uncharge)
* Functionality to extract the storage pointer from a pointer to the
owning object (map_owner_storage_ptr)
Co-developed-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: KP Singh <kpsingh@google.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200825182919.1118197-4-kpsingh@chromium.org
Don't go via map->ops to call sock_map_update_elem, since we know
what function to call in bpf_map_update_value. Since we currently
don't allow calling map_update_elem from BPF context, we can remove
ops->map_update_elem and rename the function to sock_map_update_elem_sys.
Signed-off-by: Lorenz Bauer <lmb@cloudflare.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Yonghong Song <yhs@fb.com>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Link: https://lore.kernel.org/bpf/20200821102948.21918-4-lmb@cloudflare.com
For bpf_map_elem and bpf_sk_local_storage bpf iterators,
additional map_id should be shown for fdinfo and
userspace query. For example, the following is for
a bpf_map_elem iterator.
$ cat /proc/1753/fdinfo/9
pos: 0
flags: 02000000
mnt_id: 14
link_type: iter
link_id: 34
prog_tag: 104be6d3fe45e6aa
prog_id: 173
target_name: bpf_map_elem
map_id: 127
Signed-off-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200821184419.574240-1-yhs@fb.com
This patch implemented bpf_link callback functions
show_fdinfo and fill_link_info to support link_query
interface.
The general interface for show_fdinfo and fill_link_info
will print/fill the target_name. Each targets can
register show_fdinfo and fill_link_info callbacks
to print/fill more target specific information.
For example, the below is a fdinfo result for a bpf
task iterator.
$ cat /proc/1749/fdinfo/7
pos: 0
flags: 02000000
mnt_id: 14
link_type: iter
link_id: 11
prog_tag: 990e1f8152f7e54f
prog_id: 59
target_name: task
Signed-off-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200821184418.574122-1-yhs@fb.com
Refactor the code a bit to extract bpf_link_by_id() helper.
It's similar to existing bpf_prog_by_id().
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Acked-by: Song Liu <songliubraving@fb.com>
Link: https://lore.kernel.org/bpf/20200819042759.51280-2-alexei.starovoitov@gmail.com
Commit a5cbe05a66 ("bpf: Implement bpf iterator for
map elements") added bpf iterator support for
map elements. The map element bpf iterator requires
info to identify a particular map. In the above
commit, the attr->link_create.target_fd is used
to carry map_fd and an enum bpf_iter_link_info
is added to uapi to specify the target_fd actually
representing a map_fd:
enum bpf_iter_link_info {
BPF_ITER_LINK_UNSPEC = 0,
BPF_ITER_LINK_MAP_FD = 1,
MAX_BPF_ITER_LINK_INFO,
};
This is an extensible approach as we can grow
enumerator for pid, cgroup_id, etc. and we can
unionize target_fd for pid, cgroup_id, etc.
But in the future, there are chances that
more complex customization may happen, e.g.,
for tasks, it could be filtered based on
both cgroup_id and user_id.
This patch changed the uapi to have fields
__aligned_u64 iter_info;
__u32 iter_info_len;
for additional iter_info for link_create.
The iter_info is defined as
union bpf_iter_link_info {
struct {
__u32 map_fd;
} map;
};
So future extension for additional customization
will be easier. The bpf_iter_link_info will be
passed to target callback to validate and generic
bpf_iter framework does not need to deal it any
more.
Note that map_fd = 0 will be considered invalid
and -EBADF will be returned to user space.
Fixes: a5cbe05a66 ("bpf: Implement bpf iterator for map elements")
Signed-off-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Link: https://lore.kernel.org/bpf/20200805055056.1457463-1-yhs@fb.com
Add LINK_DETACH command to force-detach bpf_link without destroying it. It has
the same behavior as auto-detaching of bpf_link due to cgroup dying for
bpf_cgroup_link or net_device being destroyed for bpf_xdp_link. In such case,
bpf_link is still a valid kernel object, but is defuncts and doesn't hold BPF
program attached to corresponding BPF hook. This functionality allows users
with enough access rights to manually force-detach attached bpf_link without
killing respective owner process.
This patch implements LINK_DETACH for cgroup, xdp, and netns links, mostly
re-using existing link release handling code.
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Song Liu <songliubraving@fb.com>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Link: https://lore.kernel.org/bpf/20200731182830.286260-2-andriin@fb.com
Similarly to bpf_prog, make bpf_link and related generic API available
unconditionally to make it easier to have bpf_link support in various parts of
the kernel. Stub out init/prime/settle/cleanup and inc/put APIs.
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200722064603.3350758-2-andriin@fb.com
Calling get_perf_callchain() on perf_events from PEBS entries may cause
unwinder errors. To fix this issue, the callchain is fetched early. Such
perf_events are marked with __PERF_SAMPLE_CALLCHAIN_EARLY.
Similarly, calling bpf_get_[stack|stackid] on perf_events from PEBS may
also cause unwinder errors. To fix this, add separate version of these
two helpers, bpf_get_[stack|stackid]_pe. These two hepers use callchain in
bpf_perf_event_data_kern->data->callchain.
Signed-off-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200723180648.1429892-2-songliubraving@fb.com
The bpf iterator for map elements are implemented.
The bpf program will receive four parameters:
bpf_iter_meta *meta: the meta data
bpf_map *map: the bpf_map whose elements are traversed
void *key: the key of one element
void *value: the value of the same element
Here, meta and map pointers are always valid, and
key has register type PTR_TO_RDONLY_BUF_OR_NULL and
value has register type PTR_TO_RDWR_BUF_OR_NULL.
The kernel will track the access range of key and value
during verification time. Later, these values will be compared
against the values in the actual map to ensure all accesses
are within range.
A new field iter_seq_info is added to bpf_map_ops which
is used to add map type specific information, i.e., seq_ops,
init/fini seq_file func and seq_file private data size.
Subsequent patches will have actual implementation
for bpf_map_ops->iter_seq_info.
In user space, BPF_ITER_LINK_MAP_FD needs to be
specified in prog attr->link_create.flags, which indicates
that attr->link_create.target_fd is a map_fd.
The reason for such an explicit flag is for possible
future cases where one bpf iterator may allow more than
one possible customization, e.g., pid and cgroup id for
task_file.
Current kernel internal implementation only allows
the target to register at most one required bpf_iter_link_info.
To support the above case, optional bpf_iter_link_info's
are needed, the target can be extended to register such link
infos, and user provided link_info needs to match one of
target supported ones.
Signed-off-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200723184112.590360-1-yhs@fb.com
Readonly and readwrite buffer register states
are introduced. Totally four states,
PTR_TO_RDONLY_BUF[_OR_NULL] and PTR_TO_RDWR_BUF[_OR_NULL]
are supported. As suggested by their respective
names, PTR_TO_RDONLY_BUF[_OR_NULL] are for
readonly buffers and PTR_TO_RDWR_BUF[_OR_NULL]
for read/write buffers.
These new register states will be used
by later bpf map element iterator.
New register states share some similarity to
PTR_TO_TP_BUFFER as it will calculate accessed buffer
size during verification time. The accessed buffer
size will be later compared to other metrics during
later attach/link_create time.
Similar to reg_state PTR_TO_BTF_ID_OR_NULL in bpf
iterator programs, PTR_TO_RDONLY_BUF_OR_NULL or
PTR_TO_RDWR_BUF_OR_NULL reg_types can be set at
prog->aux->bpf_ctx_arg_aux, and bpf verifier will
retrieve the values during btf_ctx_access().
Later bpf map element iterator implementation
will show how such information will be assigned
during target registeration time.
The verifier is also enhanced such that PTR_TO_RDONLY_BUF
can be passed to ARG_PTR_TO_MEM[_OR_NULL] helper argument, and
PTR_TO_RDWR_BUF can be passed to ARG_PTR_TO_MEM[_OR_NULL] or
ARG_PTR_TO_UNINIT_MEM.
Signed-off-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200723184111.590274-1-yhs@fb.com
This patch refactored target bpf_iter_init_seq_priv_t callback
function to accept additional information. This will be needed
in later patches for map element targets since a particular
map should be passed to traverse elements for that particular
map. In the future, other information may be passed to target
as well, e.g., pid, cgroup id, etc. to customize the iterator.
Signed-off-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200723184110.590156-1-yhs@fb.com
