linux-stable/kernel
Christian Brauner 99cdb8b9a5 seccomp: notify about unused filter
We've been making heavy use of the seccomp notifier to intercept and
handle certain syscalls for containers. This patch allows a syscall
supervisor listening on a given notifier to be notified when a seccomp
filter has become unused.

A container is often managed by a singleton supervisor process the
so-called "monitor". This monitor process has an event loop which has
various event handlers registered. If the user specified a seccomp
profile that included a notifier for various syscalls then we also
register a seccomp notify even handler. For any container using a
separate pid namespace the lifecycle of the seccomp notifier is bound to
the init process of the pid namespace, i.e. when the init process exits
the filter must be unused.

If a new process attaches to a container we force it to assume a seccomp
profile. This can either be the same seccomp profile as the container
was started with or a modified one. If the attaching process makes use
of the seccomp notifier we will register a new seccomp notifier handler
in the monitor's event loop. However, when the attaching process exits
we can't simply delete the handler since other child processes could've
been created (daemons spawned etc.) that have inherited the seccomp
filter and so we need to keep the seccomp notifier fd alive in the event
loop. But this is problematic since we don't get a notification when the
seccomp filter has become unused and so we currently never remove the
seccomp notifier fd from the event loop and just keep accumulating fds
in the event loop. We've had this issue for a while but it has recently
become more pressing as more and larger users make use of this.

To fix this, we introduce a new "users" reference counter that tracks any
tasks and dependent filters making use of a filter. When a notifier is
registered waiting tasks will be notified that the filter is now empty
by receiving a (E)POLLHUP event.

The concept in this patch introduces is the same as for signal_struct,
i.e. reference counting for life-cycle management is decoupled from
reference counting taks using the object. There's probably some trickery
possible but the second counter is just the correct way of doing this
IMHO and has precedence.

Cc: Tycho Andersen <tycho@tycho.ws>
Cc: Kees Cook <keescook@chromium.org>
Cc: Matt Denton <mpdenton@google.com>
Cc: Sargun Dhillon <sargun@sargun.me>
Cc: Jann Horn <jannh@google.com>
Cc: Chris Palmer <palmer@google.com>
Cc: Aleksa Sarai <cyphar@cyphar.com>
Cc: Robert Sesek <rsesek@google.com>
Cc: Jeffrey Vander Stoep <jeffv@google.com>
Cc: Linux Containers <containers@lists.linux-foundation.org>
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
Link: https://lore.kernel.org/r/20200531115031.391515-3-christian.brauner@ubuntu.com
Signed-off-by: Kees Cook <keescook@chromium.org>
2020-07-10 16:01:51 -07:00
..
bpf Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2020-06-13 16:27:13 -07:00
cgroup mmap locking API: convert mmap_sem comments 2020-06-09 09:39:14 -07:00
configs compiler: remove CONFIG_OPTIMIZE_INLINING entirely 2020-04-07 10:43:42 -07:00
debug kernel: rename show_stack_loglvl() => show_stack() 2020-06-09 09:39:13 -07:00
dma dma-mapping updates for 5.8, part 1 2020-06-06 11:43:23 -07:00
events Merge branch 'akpm' (patches from Andrew) 2020-06-09 09:54:46 -07:00
gcov treewide: replace '---help---' in Kconfig files with 'help' 2020-06-14 01:57:21 +09:00
irq treewide: replace '---help---' in Kconfig files with 'help' 2020-06-14 01:57:21 +09:00
kcsan kcsan: Support distinguishing volatile accesses 2020-06-11 20:04:01 +02:00
livepatch livepatch: Make klp_apply_object_relocs static 2020-05-11 00:31:38 +02:00
locking The X86 entry, exception and interrupt code rework 2020-06-13 10:05:47 -07:00
power treewide: replace '---help---' in Kconfig files with 'help' 2020-06-14 01:57:21 +09:00
printk One more printk change for 5.8 2020-06-12 12:13:36 -07:00
rcu TTY/Serial driver updates for 5.8-rc1 2020-06-07 09:52:36 -07:00
sched Rebase locking/kcsan to locking/urgent 2020-06-11 20:02:46 +02:00
time The X86 entry, exception and interrupt code rework 2020-06-13 10:05:47 -07:00
trace Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2020-06-13 16:27:13 -07:00
.gitignore .gitignore: add SPDX License Identifier 2020-03-25 11:50:48 +01:00
acct.c mmap locking API: convert mmap_sem comments 2020-06-09 09:39:14 -07:00
async.c
audit.c audit/stable-5.8 PR 20200601 2020-06-02 17:13:37 -07:00
audit.h audit: fix a net reference leak in audit_list_rules_send() 2020-04-22 15:23:10 -04:00
audit_fsnotify.c fsnotify: use helpers to access data by data_type 2020-03-23 18:19:06 +01:00
audit_tree.c
audit_watch.c \n 2020-04-06 08:58:42 -07:00
auditfilter.c audit: fix a net reference leak in audit_list_rules_send() 2020-04-22 15:23:10 -04:00
auditsc.c audit: add subj creds to NETFILTER_CFG record to 2020-05-20 18:09:19 -04:00
backtracetest.c
bounds.c
capability.c
compat.c uaccess: Selectively open read or write user access 2020-05-01 12:35:21 +10:00
configs.c proc: convert everything to "struct proc_ops" 2020-02-04 03:05:26 +00:00
context_tracking.c context_tracking: Ensure that the critical path cannot be instrumented 2020-06-11 15:14:36 +02:00
cpu.c The changes in this cycle are: 2020-06-03 13:06:42 -07:00
cpu_pm.c kernel/cpu_pm: Fix uninitted local in cpu_pm 2020-05-15 11:44:34 -07:00
crash_core.c
crash_dump.c crash_dump: Remove no longer used saved_max_pfn 2020-04-15 11:21:54 +02:00
cred.c exec: Teach prepare_exec_creds how exec treats uids & gids 2020-05-20 14:44:21 -05:00
delayacct.c
dma.c
elfcore.c
exec_domain.c
exit.c seccomp: release filter after task is fully dead 2020-07-10 16:01:51 -07:00
extable.c kernel/extable.c: use address-of operator on section symbols 2020-04-07 10:43:42 -07:00
fail_function.c
fork.c seccomp: release filter after task is fully dead 2020-07-10 16:01:51 -07:00
freezer.c
futex.c mmap locking API: use coccinelle to convert mmap_sem rwsem call sites 2020-06-09 09:39:14 -07:00
gen_kheaders.sh kbuild: add variables for compression tools 2020-06-06 23:42:01 +09:00
groups.c mm: remove the pgprot argument to __vmalloc 2020-06-02 10:59:11 -07:00
hung_task.c kernel/hung_task.c: introduce sysctl to print all traces when a hung task is detected 2020-06-08 11:05:56 -07:00
iomem.c
irq_work.c irq_work, smp: Allow irq_work on call_single_queue 2020-05-28 10:54:15 +02:00
jump_label.c
kallsyms.c kallsyms: unexport kallsyms_lookup_name() and kallsyms_on_each_symbol() 2020-04-07 10:43:44 -07:00
kcmp.c kernel/kcmp.c: Use new infrastructure to fix deadlocks in execve 2020-03-25 10:04:01 -05:00
Kconfig.freezer
Kconfig.hz
Kconfig.locks
Kconfig.preempt
kcov.c kcov: check kcov_softirq in kcov_remote_stop() 2020-06-10 19:14:17 -07:00
kexec.c
kexec_core.c
kexec_elf.c
kexec_file.c kexec_file: don't place kexec images on IORESOURCE_MEM_DRIVER_MANAGED 2020-06-04 19:06:23 -07:00
kexec_internal.h
kheaders.c
kmod.c kmod: make request_module() return an error when autoloading is disabled 2020-04-10 15:36:22 -07:00
kprobes.c kernel/kprobes.c: convert to use DEFINE_SEQ_ATTRIBUTE macro 2020-06-04 19:06:26 -07:00
ksysfs.c
kthread.c Merge branch 'akpm' (patches from Andrew) 2020-06-11 13:25:53 -07:00
latencytop.c sysctl: pass kernel pointers to ->proc_handler 2020-04-27 02:07:40 -04:00
Makefile Notifications over pipes + Keyring notifications 2020-06-13 09:56:21 -07:00
module-internal.h
module.c module: move the set_fs hack for flush_icache_range to m68k 2020-06-08 11:05:58 -07:00
module_signature.c
module_signing.c
notifier.c mm: remove vmalloc_sync_(un)mappings() 2020-06-02 10:59:12 -07:00
nsproxy.c nsproxy: attach to namespaces via pidfds 2020-05-13 11:41:22 +02:00
padata.c padata: add basic support for multithreaded jobs 2020-06-03 20:09:45 -07:00
panic.c bug: Annotate WARN/BUG/stackfail as noinstr safe 2020-06-11 15:14:36 +02:00
params.c
pid.c remove the no longer needed pid_alive() check in __task_pid_nr_ns() 2020-04-30 06:40:14 -05:00
pid_namespace.c Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next 2020-06-03 16:27:18 -07:00
profile.c proc: convert everything to "struct proc_ops" 2020-02-04 03:05:26 +00:00
ptrace.c ptrace: reintroduce usage of subjective credentials in ptrace_has_cap() 2020-01-18 13:51:39 +01:00
range.c
reboot.c printk: Collapse shutdown types into a single dump reason 2020-05-30 10:34:03 -07:00
relay.c mmap locking API: convert mmap_sem comments 2020-06-09 09:39:14 -07:00
resource.c /dev/mem: Revoke mappings when a driver claims the region 2020-05-27 11:10:05 +02:00
rseq.c
scs.c scs: Report SCS usage in bytes rather than number of entries 2020-06-04 16:14:56 +01:00
seccomp.c seccomp: notify about unused filter 2020-07-10 16:01:51 -07:00
signal.c Merge branch 'work.set_fs-exec' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2020-06-01 16:21:46 -07:00
smp.c The changes in this cycle are: 2020-06-03 13:06:42 -07:00
smpboot.c
smpboot.h
softirq.c x86/entry: Clarify irq_{enter,exit}_rcu() 2020-06-11 15:15:24 +02:00
stackleak.c
stacktrace.c
stop_machine.c stop_machine: Make stop_cpus() static 2020-01-17 10:19:21 +01:00
sys.c Add additional LSM hooks for SafeSetID 2020-06-14 11:39:31 -07:00
sys_ni.c
sysctl-test.c
sysctl.c kernel/sysctl.c: ignore out-of-range taint bits introduced via kernel.tainted 2020-06-08 11:05:56 -07:00
sysctl_binary.c
task_work.c task_work_run: don't take ->pi_lock unconditionally 2020-03-02 14:06:33 -07:00
taskstats.c
test_kprobes.c
torture.c CPU (hotplug) updates: 2020-03-30 18:06:39 -07:00
tracepoint.c
tsacct.c
ucount.c ucount: Make sure ucounts in /proc/sys/user don't regress again 2020-04-07 21:51:27 +02:00
uid16.c
uid16.h
umh.c Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2020-05-15 13:48:59 -07:00
up.c smp/up: Make smp_call_function_single() match SMP semantics 2020-02-07 15:34:12 +01:00
user-return-notifier.c
user.c user.c: make uidhash_table static 2020-06-04 19:06:24 -07:00
user_namespace.c nsproxy: add struct nsset 2020-05-09 13:57:12 +02:00
utsname.c nsproxy: add struct nsset 2020-05-09 13:57:12 +02:00
utsname_sysctl.c sysctl: pass kernel pointers to ->proc_handler 2020-04-27 02:07:40 -04:00
watch_queue.c Notifications over pipes + Keyring notifications 2020-06-13 09:56:21 -07:00
watchdog.c kernel/watchdog.c: convert {soft/hard}lockup boot parameters to sysctl aliases 2020-06-08 11:05:56 -07:00
watchdog_hld.c
workqueue.c workqueue: use BUILD_BUG_ON() for compile time test instead of WARN_ON() 2020-06-01 11:02:42 -04:00
workqueue_internal.h