Commit 1af2dface5 ("af_unix: Don't access successor in unix_del_edges()
during GC.") fixed use-after-free by avoid accessing edge->successor while
GC is in progress.
However, there could be a small race window where another process could
call unix_del_edges() while gc_in_progress is true and __skb_queue_purge()
is on the way.
So, we need another marker for struct scm_fp_list which indicates if the
skb is garbage-collected.
This patch adds dead flag in struct scm_fp_list and set it true before
calling __skb_queue_purge().
Fixes: 1af2dface5 ("af_unix: Don't access successor in unix_del_edges() during GC.")
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Acked-by: Paolo Abeni <pabeni@redhat.com>
Link: https://lore.kernel.org/r/20240508171150.50601-1-kuniyu@amazon.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
As with the previous patch, we preallocate to skb's scm_fp_list an
array of struct unix_edge in the number of inflight AF_UNIX fds.
There we just preallocate memory and do not use immediately because
sendmsg() could fail after this point. The actual use will be in
the next patch.
When we queue skb with inflight edges, we will set the inflight
socket's unix_sock as unix_edge->predecessor and the receiver's
unix_sock as successor, and then we will link the edge to the
inflight socket's unix_vertex.edges.
Note that we set NULL to cloned scm_fp_list.edges in scm_fp_dup()
so that MSG_PEEK does not change the shape of the directed graph.
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Acked-by: Paolo Abeni <pabeni@redhat.com>
Link: https://lore.kernel.org/r/20240325202425.60930-3-kuniyu@amazon.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
We will replace the garbage collection algorithm for AF_UNIX, where
we will consider each inflight AF_UNIX socket as a vertex and its file
descriptor as an edge in a directed graph.
This patch introduces a new struct unix_vertex representing a vertex
in the graph and adds its pointer to struct unix_sock.
When we send a fd using the SCM_RIGHTS message, we allocate struct
scm_fp_list to struct scm_cookie in scm_fp_copy(). Then, we bump
each refcount of the inflight fds' struct file and save them in
scm_fp_list.fp.
After that, unix_attach_fds() inexplicably clones scm_fp_list of
scm_cookie and sets it to skb. (We will remove this part after
replacing GC.)
Here, we add a new function call in unix_attach_fds() to preallocate
struct unix_vertex per inflight AF_UNIX fd and link each vertex to
skb's scm_fp_list.vertices.
When sendmsg() succeeds later, if the socket of the inflight fd is
still not inflight yet, we will set the preallocated vertex to struct
unix_sock.vertex and link it to a global list unix_unvisited_vertices
under spin_lock(&unix_gc_lock).
If the socket is already inflight, we free the preallocated vertex.
This is to avoid taking the lock unnecessarily when sendmsg() could
fail later.
In the following patch, we will similarly allocate another struct
per edge, which will finally be linked to the inflight socket's
unix_vertex.edges.
And then, we will count the number of edges as unix_vertex.out_degree.
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Acked-by: Paolo Abeni <pabeni@redhat.com>
Link: https://lore.kernel.org/r/20240325202425.60930-2-kuniyu@amazon.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
If more than 16000 inflight AF_UNIX sockets exist and the garbage
collector is not running, unix_(dgram|stream)_sendmsg() call unix_gc().
Also, they wait for unix_gc() to complete.
In unix_gc(), all inflight AF_UNIX sockets are traversed at least once,
and more if they are the GC candidate. Thus, sendmsg() significantly
slows down with too many inflight AF_UNIX sockets.
However, if a process sends data with no AF_UNIX FD, the sendmsg() call
does not need to wait for GC. After this change, only the process that
meets the condition below will be blocked under such a situation.
1) cmsg contains AF_UNIX socket
2) more than 32 AF_UNIX sent by the same user are still inflight
Note that even a sendmsg() call that does not meet the condition but has
AF_UNIX FD will be blocked later in unix_scm_to_skb() by the spinlock,
but we allow that as a bonus for sane users.
The results below are the time spent in unix_dgram_sendmsg() sending 1
byte of data with no FD 4096 times on a host where 32K inflight AF_UNIX
sockets exist.
Without series: the sane sendmsg() needs to wait gc unreasonably.
$ sudo /usr/share/bcc/tools/funclatency -p 11165 unix_dgram_sendmsg
Tracing 1 functions for "unix_dgram_sendmsg"... Hit Ctrl-C to end.
^C
nsecs : count distribution
[...]
524288 -> 1048575 : 0 | |
1048576 -> 2097151 : 3881 |****************************************|
2097152 -> 4194303 : 214 |** |
4194304 -> 8388607 : 1 | |
avg = 1825567 nsecs, total: 7477526027 nsecs, count: 4096
With series: the sane sendmsg() can finish much faster.
$ sudo /usr/share/bcc/tools/funclatency -p 8702 unix_dgram_sendmsg
Tracing 1 functions for "unix_dgram_sendmsg"... Hit Ctrl-C to end.
^C
nsecs : count distribution
[...]
128 -> 255 : 0 | |
256 -> 511 : 4092 |****************************************|
512 -> 1023 : 2 | |
1024 -> 2047 : 0 | |
2048 -> 4095 : 0 | |
4096 -> 8191 : 1 | |
8192 -> 16383 : 1 | |
avg = 410 nsecs, total: 1680510 nsecs, count: 4096
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Link: https://lore.kernel.org/r/20240123170856.41348-6-kuniyu@amazon.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Since we no longer allow sending io_uring fds over SCM_RIGHTS, move to
using io_is_uring_fops() to detect whether this is a io_uring fd or not.
With that done, kill off io_uring_get_socket() as nobody calls it
anymore.
This is in preparation to yanking out the rest of the core related to
unix gc with io_uring.
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Merge vfs.file from the VFS tree to avoid conflicts with receive_fd() now
having 3 arguments rather than just 2.
* 'vfs.file' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs:
file: remove __receive_fd()
file: stop exposing receive_fd_user()
fs: replace f_rcuhead with f_task_work
file: remove pointless wrapper
file: s/close_fd_get_file()/file_close_fd()/g
Improve __fget_files_rcu() code generation (and thus __fget_light())
file: massage cleanup of files that failed to open
Not every subsystem needs to have their own specialized helper.
Just us the __receive_fd() helper.
Link: https://lore.kernel.org/r/20231130-vfs-files-fixes-v1-4-e73ca6f4ea83@kernel.org
Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Christian Brauner <brauner@kernel.org>
File reference cycles have caused lots of problems for io_uring
in the past, and it still doesn't work exactly right and races with
unix_stream_read_generic(). The safest fix would be to completely
disallow sending io_uring files via sockets via SCM_RIGHT, so there
are no possible cycles invloving registered files and thus rendering
SCM accounting on the io_uring side unnecessary.
Cc: <stable@vger.kernel.org>
Fixes: 0091bfc817 ("io_uring/af_unix: defer registered files gc to io_uring release")
Reported-and-suggested-by: Jann Horn <jannh@google.com>
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/c716c88321939156909cfa1bd8b0faaf1c804103.1701868795.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
IPV6_ADDRFORM socket option is evil, because it can change sock->ops
while other threads might read it. Same issue for sk->sk_family
being set to AF_INET.
Adding READ_ONCE() over sock->ops reads is needed for sockets
that might be impacted by IPV6_ADDRFORM.
Note that mptcp_is_tcpsk() can also overwrite sock->ops.
Adding annotations for all sk->sk_family reads will require
more patches :/
BUG: KCSAN: data-race in ____sys_sendmsg / do_ipv6_setsockopt
write to 0xffff888109f24ca0 of 8 bytes by task 4470 on cpu 0:
do_ipv6_setsockopt+0x2c5e/0x2ce0 net/ipv6/ipv6_sockglue.c:491
ipv6_setsockopt+0x57/0x130 net/ipv6/ipv6_sockglue.c:1012
udpv6_setsockopt+0x95/0xa0 net/ipv6/udp.c:1690
sock_common_setsockopt+0x61/0x70 net/core/sock.c:3663
__sys_setsockopt+0x1c3/0x230 net/socket.c:2273
__do_sys_setsockopt net/socket.c:2284 [inline]
__se_sys_setsockopt net/socket.c:2281 [inline]
__x64_sys_setsockopt+0x66/0x80 net/socket.c:2281
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd
read to 0xffff888109f24ca0 of 8 bytes by task 4469 on cpu 1:
sock_sendmsg_nosec net/socket.c:724 [inline]
sock_sendmsg net/socket.c:747 [inline]
____sys_sendmsg+0x349/0x4c0 net/socket.c:2503
___sys_sendmsg net/socket.c:2557 [inline]
__sys_sendmmsg+0x263/0x500 net/socket.c:2643
__do_sys_sendmmsg net/socket.c:2672 [inline]
__se_sys_sendmmsg net/socket.c:2669 [inline]
__x64_sys_sendmmsg+0x57/0x60 net/socket.c:2669
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd
value changed: 0xffffffff850e32b8 -> 0xffffffff850da890
Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 4469 Comm: syz-executor.1 Not tainted 6.4.0-rc5-syzkaller-00313-g4c605260bc60 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/25/2023
Reported-by: syzbot <syzkaller@googlegroups.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Link: https://lore.kernel.org/r/20230808135809.2300241-1-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Since commit 1f466e1f15 ("net: cleanly handle kernel vs user
buffers for ->msg_control"), pointers to user buffers should be
stored in struct msghdr::msg_control_user, instead of the
msg_control field. Most users of msg_control have already been
converted (where user buffers are involved), but not all of them.
This patch attempts to address the remaining cases. An exception is
made for null checks, as it should be safe to use msg_control
unconditionally for that purpose.
Cc: Christoph Hellwig <hch@lst.de>
Cc: Eric Dumazet <edumazet@google.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Kevin Brodsky <kevin.brodsky@arm.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: David S. Miller <davem@davemloft.net>
This is a followup of commit 2558b8039d ("net: use a bounce
buffer for copying skb->mark")
x86 and powerpc define user_access_begin, meaning
that they are not able to perform user copy checks
when using user_write_access_begin() / unsafe_copy_to_user()
and friends [1]
Instead of waiting bugs to trigger on other arches,
add a check_object_size() in put_cmsg() to make sure
that new code tested on x86 with CONFIG_HARDENED_USERCOPY=y
will perform more security checks.
[1] We can not generically call check_object_size() from
unsafe_copy_to_user() because UACCESS is enabled at this point.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Kees Cook <keescook@chromium.org>
Acked-by: Kees Cook <keescook@chromium.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
unix sockets allows to send file descriptors via SCM_RIGHTS type messages.
Each such send call forces kernel to allocate up to 2Kb memory for
struct scm_fp_list.
It makes sense to account for them to restrict the host's memory
consumption from inside the memcg-limited container.
Signed-off-by: Vasily Averin <vvs@virtuozzo.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
We need to store cmlen instead of len in cm->cmsg_len.
Fixes: 38ebcf5096 ("scm: optimize put_cmsg()")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Calling two copy_to_user() for very small regions has very high overhead.
Switch to inlined unsafe_put_user() to save one stac/clac sequence,
and avoid copy_to_user().
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Soheil Hassas Yeganeh <soheil@google.com>
Acked-by: Soheil Hassas Yeganeh <soheil@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
For both pidfd and seccomp, the __user pointer is not used. Update
__receive_fd() to make writing to ufd optional via a NULL check. However,
for the receive_fd_user() wrapper, ufd is NULL checked so an -EFAULT
can be returned to avoid changing the SCM_RIGHTS interface behavior. Add
new wrapper receive_fd() for pidfd and seccomp that does not use the ufd
argument. For the new helper, the allocated fd needs to be returned on
success. Update the existing callers to handle it.
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: linux-fsdevel@vger.kernel.org
Reviewed-by: Sargun Dhillon <sargun@sargun.me>
Acked-by: Christian Brauner <christian.brauner@ubuntu.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
In preparation for users of the "install a received file" logic outside
of net/ (pidfd and seccomp), relocate and rename __scm_install_fd() from
net/core/scm.c to __receive_fd() in fs/file.c, and provide a wrapper
named receive_fd_user(), as future patches will change the interface
to __receive_fd().
Additionally add a comment to fd_install() as a counterpoint to how
__receive_fd() interacts with fput().
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: Dmitry Kadashev <dkadashev@gmail.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Sargun Dhillon <sargun@sargun.me>
Cc: Ido Schimmel <idosch@idosch.org>
Cc: Ioana Ciornei <ioana.ciornei@nxp.com>
Cc: linux-fsdevel@vger.kernel.org
Cc: netdev@vger.kernel.org
Reviewed-by: Sargun Dhillon <sargun@sargun.me>
Acked-by: Christian Brauner <christian.brauner@ubuntu.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Duplicate the cleanups from commit 2618d530dd ("net/scm: cleanup
scm_detach_fds") into the compat code.
Replace open-coded __receive_sock() with a call to the helper.
Move the check added in commit 1f466e1f15 ("net: cleanly handle kernel
vs user buffers for ->msg_control") to before the compat call, even
though it should be impossible for an in-kernel call to also be compat.
Correct the int "flags" argument to unsigned int to match fd_install()
and similar APIs.
Regularize any remaining differences, including a whitespace issue,
a checkpatch warning, and add the check from commit 6900317f5e ("net,
scm: fix PaX detected msg_controllen overflow in scm_detach_fds") which
fixed an overflow unique to 64-bit. To avoid confusion when comparing
the compat handler to the native handler, just include the same check
in the compat handler.
Cc: Christoph Hellwig <hch@lst.de>
Cc: Sargun Dhillon <sargun@sargun.me>
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: netdev@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Acked-by: Christian Brauner <christian.brauner@ubuntu.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
The code had historically been ignoring these errors, and my recent
refactoring changed that, which broke ssh in some setups.
Fixes: 2618d530dd ("net/scm: cleanup scm_detach_fds")
Reported-by: Ido Schimmel <idosch@idosch.org>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Tested-by: Ido Schimmel <idosch@mellanox.com>
Tested-by: Ioana Ciornei <ioana.ciornei@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
The msg_control field in struct msghdr can either contain a user
pointer when used with the recvmsg system call, or a kernel pointer
when used with sendmsg. To complicate things further kernel_recvmsg
can stuff a kernel pointer in and then use set_fs to make the uaccess
helpers accept it.
Replace it with a union of a kernel pointer msg_control field, and
a user pointer msg_control_user one, and allow kernel_recvmsg operate
on a proper kernel pointer using a bitfield to override the normal
choice of a user pointer for recvmsg.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: David S. Miller <davem@davemloft.net>
Add a variant of CMSG_DATA that operates on user pointer to avoid
sparse warnings about casting to/from user pointers. Also fix up
CMSG_DATA to rely on the gcc extension that allows void pointer
arithmetics to cut down on the amount of casts.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: David S. Miller <davem@davemloft.net>
In order to remove the 'struct timespec' definition and the
timespec64_to_timespec() helper function, change over the in-kernel
definition of 'struct scm_timestamping' to use the __kernel_old_timespec
replacement and open-code the assignment.
Acked-by: Deepa Dinamani <deepa.kernel@gmail.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Based on 1 normalized pattern(s):
this program is free software you can redistribute it and or modify
it under the terms of the gnu general public license as published by
the free software foundation either version 2 of the license or at
your option any later version
extracted by the scancode license scanner the SPDX license identifier
GPL-2.0-or-later
has been chosen to replace the boilerplate/reference in 3029 file(s).
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Allison Randal <allison@lohutok.net>
Cc: linux-spdx@vger.kernel.org
Link: https://lkml.kernel.org/r/20190527070032.746973796@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
We are going to split <linux/sched/user.h> out of <linux/sched.h>, which
will have to be picked up from other headers and a couple of .c files.
Create a trivial placeholder <linux/sched/user.h> file that just
maps to <linux/sched.h> to make this patch obviously correct and
bisectable.
Include the new header in the files that are going to need it.
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
sizeof(struct cmsghdr) and sizeof(struct compat_cmsghdr) already aligned.
remove use CMSG_ALIGN(sizeof(struct cmsghdr)) and
CMSG_COMPAT_ALIGN(sizeof(struct compat_cmsghdr)) keep code consistent.
Signed-off-by: yuan linyu <Linyu.Yuan@alcatel-sbell.com.cn>
Signed-off-by: David S. Miller <davem@davemloft.net>
This was entirely automated, using the script by Al:
PATT='^[[:blank:]]*#[[:blank:]]*include[[:blank:]]*<asm/uaccess.h>'
sed -i -e "s!$PATT!#include <linux/uaccess.h>!" \
$(git grep -l "$PATT"|grep -v ^include/linux/uaccess.h)
to do the replacement at the end of the merge window.
Requested-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The commit referenced in the Fixes tag incorrectly accounted the number
of in-flight fds over a unix domain socket to the original opener
of the file-descriptor. This allows another process to arbitrary
deplete the original file-openers resource limit for the maximum of
open files. Instead the sending processes and its struct cred should
be credited.
To do so, we add a reference counted struct user_struct pointer to the
scm_fp_list and use it to account for the number of inflight unix fds.
Fixes: 712f4aad40 ("unix: properly account for FDs passed over unix sockets")
Reported-by: David Herrmann <dh.herrmann@gmail.com>
Cc: David Herrmann <dh.herrmann@gmail.com>
Cc: Willy Tarreau <w@1wt.eu>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Introduce sock->sk_cgrp_data which is a struct sock_cgroup_data.
->sk_cgroup_prioidx and ->sk_classid are moved into it. The struct
and its accessors are defined in cgroup-defs.h. This is to prepare
for overloading the fields with a cgroup pointer.
This patch mostly performs equivalent conversions but the followings
are noteworthy.
* Equality test before updating classid is removed from
sock_update_classid(). This shouldn't make any noticeable
difference and a similar test will be implemented on the helper side
later.
* sock_update_netprioidx() now takes struct sock_cgroup_data and can
be moved to netprio_cgroup.h without causing include dependency
loop. Moved.
* The dummy version of sock_update_netprioidx() converted to a static
inline function while at it.
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
David and HacKurx reported a following/similar size overflow triggered
in a grsecurity kernel, thanks to PaX's gcc size overflow plugin:
(Already fixed in later grsecurity versions by Brad and PaX Team.)
[ 1002.296137] PAX: size overflow detected in function scm_detach_fds net/core/scm.c:314
cicus.202_127 min, count: 4, decl: msg_controllen; num: 0; context: msghdr;
[ 1002.296145] CPU: 0 PID: 3685 Comm: scm_rights_recv Not tainted 4.2.3-grsec+ #7
[ 1002.296149] Hardware name: Apple Inc. MacBookAir5,1/Mac-66F35F19FE2A0D05, [...]
[ 1002.296153] ffffffff81c27366 0000000000000000 ffffffff81c27375 ffffc90007843aa8
[ 1002.296162] ffffffff818129ba 0000000000000000 ffffffff81c27366 ffffc90007843ad8
[ 1002.296169] ffffffff8121f838 fffffffffffffffc fffffffffffffffc ffffc90007843e60
[ 1002.296176] Call Trace:
[ 1002.296190] [<ffffffff818129ba>] dump_stack+0x45/0x57
[ 1002.296200] [<ffffffff8121f838>] report_size_overflow+0x38/0x60
[ 1002.296209] [<ffffffff816a979e>] scm_detach_fds+0x2ce/0x300
[ 1002.296220] [<ffffffff81791899>] unix_stream_read_generic+0x609/0x930
[ 1002.296228] [<ffffffff81791c9f>] unix_stream_recvmsg+0x4f/0x60
[ 1002.296236] [<ffffffff8178dc00>] ? unix_set_peek_off+0x50/0x50
[ 1002.296243] [<ffffffff8168fac7>] sock_recvmsg+0x47/0x60
[ 1002.296248] [<ffffffff81691522>] ___sys_recvmsg+0xe2/0x1e0
[ 1002.296257] [<ffffffff81693496>] __sys_recvmsg+0x46/0x80
[ 1002.296263] [<ffffffff816934fc>] SyS_recvmsg+0x2c/0x40
[ 1002.296271] [<ffffffff8181a3ab>] entry_SYSCALL_64_fastpath+0x12/0x85
Further investigation showed that this can happen when an *odd* number of
fds are being passed over AF_UNIX sockets.
In these cases CMSG_LEN(i * sizeof(int)) and CMSG_SPACE(i * sizeof(int)),
where i is the number of successfully passed fds, differ by 4 bytes due
to the extra CMSG_ALIGN() padding in CMSG_SPACE() to an 8 byte boundary
on 64 bit. The padding is used to align subsequent cmsg headers in the
control buffer.
When the control buffer passed in from the receiver side *lacks* these 4
bytes (e.g. due to buggy/wrong API usage), then msg->msg_controllen will
overflow in scm_detach_fds():
int cmlen = CMSG_LEN(i * sizeof(int)); <--- cmlen w/o tail-padding
err = put_user(SOL_SOCKET, &cm->cmsg_level);
if (!err)
err = put_user(SCM_RIGHTS, &cm->cmsg_type);
if (!err)
err = put_user(cmlen, &cm->cmsg_len);
if (!err) {
cmlen = CMSG_SPACE(i * sizeof(int)); <--- cmlen w/ 4 byte extra tail-padding
msg->msg_control += cmlen;
msg->msg_controllen -= cmlen; <--- iff no tail-padding space here ...
} ... wrap-around
F.e. it will wrap to a length of 18446744073709551612 bytes in case the
receiver passed in msg->msg_controllen of 20 bytes, and the sender
properly transferred 1 fd to the receiver, so that its CMSG_LEN results
in 20 bytes and CMSG_SPACE in 24 bytes.
In case of MSG_CMSG_COMPAT (scm_detach_fds_compat()), I haven't seen an
issue in my tests as alignment seems always on 4 byte boundary. Same
should be in case of native 32 bit, where we end up with 4 byte boundaries
as well.
In practice, passing msg->msg_controllen of 20 to recvmsg() while receiving
a single fd would mean that on successful return, msg->msg_controllen is
being set by the kernel to 24 bytes instead, thus more than the input
buffer advertised. It could f.e. become an issue if such application later
on zeroes or copies the control buffer based on the returned msg->msg_controllen
elsewhere.
Maximum number of fds we can send is a hard upper limit SCM_MAX_FD (253).
Going over the code, it seems like msg->msg_controllen is not being read
after scm_detach_fds() in scm_recv() anymore by the kernel, good!
Relevant recvmsg() handler are unix_dgram_recvmsg() (unix_seqpacket_recvmsg())
and unix_stream_recvmsg(). Both return back to their recvmsg() caller,
and ___sys_recvmsg() places the updated length, that is, new msg_control -
old msg_control pointer into msg->msg_controllen (hence the 24 bytes seen
in the example).
Long time ago, Wei Yongjun fixed something related in commit 1ac70e7ad2
("[NET]: Fix function put_cmsg() which may cause usr application memory
overflow").
RFC3542, section 20.2. says:
The fields shown as "XX" are possible padding, between the cmsghdr
structure and the data, and between the data and the next cmsghdr
structure, if required by the implementation. While sending an
application may or may not include padding at the end of last
ancillary data in msg_controllen and implementations must accept both
as valid. On receiving a portable application must provide space for
padding at the end of the last ancillary data as implementations may
copy out the padding at the end of the control message buffer and
include it in the received msg_controllen. When recvmsg() is called
if msg_controllen is too small for all the ancillary data items
including any trailing padding after the last item an implementation
may set MSG_CTRUNC.
Since we didn't place MSG_CTRUNC for already quite a long time, just do
the same as in 1ac70e7ad2 to avoid an overflow.
Btw, even man-page author got this wrong :/ See db939c9b26e9 ("cmsg.3: Fix
error in SCM_RIGHTS code sample"). Some people must have copied this (?),
thus it got triggered in the wild (reported several times during boot by
David and HacKurx).
No Fixes tag this time as pre 2002 (that is, pre history tree).
Reported-by: David Sterba <dave@jikos.cz>
Reported-by: HacKurx <hackurx@gmail.com>
Cc: PaX Team <pageexec@freemail.hu>
Cc: Emese Revfy <re.emese@gmail.com>
Cc: Brad Spengler <spender@grsecurity.net>
Cc: Wei Yongjun <yongjun_wei@trendmicro.com.cn>
Cc: Eric Dumazet <edumazet@google.com>
Reviewed-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
Introduce helper macro for_each_cmsghdr as a wrapper of the enumerating
cmsghdr from msghdr, just cleanup.
Signed-off-by: Gu Zheng <guz.fnst@cn.fujitsu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Pull namespace changes from Eric Biederman:
"This is an assorted mishmash of small cleanups, enhancements and bug
fixes.
The major theme is user namespace mount restrictions. nsown_capable
is killed as it encourages not thinking about details that need to be
considered. A very hard to hit pid namespace exiting bug was finally
tracked and fixed. A couple of cleanups to the basic namespace
infrastructure.
Finally there is an enhancement that makes per user namespace
capabilities usable as capabilities, and an enhancement that allows
the per userns root to nice other processes in the user namespace"
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace:
userns: Kill nsown_capable it makes the wrong thing easy
capabilities: allow nice if we are privileged
pidns: Don't have unshare(CLONE_NEWPID) imply CLONE_THREAD
userns: Allow PR_CAPBSET_DROP in a user namespace.
namespaces: Simplify copy_namespaces so it is clear what is going on.
pidns: Fix hang in zap_pid_ns_processes by sending a potentially extra wakeup
sysfs: Restrict mounting sysfs
userns: Better restrictions on when proc and sysfs can be mounted
vfs: Don't copy mount bind mounts of /proc/<pid>/ns/mnt between namespaces
kernel/nsproxy.c: Improving a snippet of code.
proc: Restrict mounting the proc filesystem
vfs: Lock in place mounts from more privileged users
nsown_capable is a special case of ns_capable essentially for just CAP_SETUID and
CAP_SETGID. For the existing users it doesn't noticably simplify things and
from the suggested patches I have seen it encourages people to do the wrong
thing. So remove nsown_capable.
Acked-by: Serge Hallyn <serge.hallyn@canonical.com>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
This is a security bug.
The follow-up will fix nsproxy to discourage this type of issue from
happening again.
Cc: stable@vger.kernel.org
Signed-off-by: Andy Lutomirski <luto@amacapital.net>
Reviewed-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
The callers always pass current to sock_update_netprio().
Signed-off-by: Li Zefan <lizefan@huawei.com>
Acked-by: Neil Horman <nhorman@tuxdriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
The callers always pass current to sock_update_classid().
Signed-off-by: Li Zefan <lizefan@huawei.com>
Acked-by: Neil Horman <nhorman@tuxdriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Now that uids and gids are completely encapsulated in kuid_t
and kgid_t we no longer need to pass struct cred which allowed
us to test both the uid and the user namespace for equality.
Passing struct cred potentially allows us to pass the entire group
list as BSD does but I don't believe the cost of cache line misses
justifies retaining code for a future potential application.
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Don't allow spoofing pids over unix domain sockets in the corner
cases where a user has created a user namespace but has not yet
created a pid namespace.
Cc: stable@vger.kernel.org
Reported-by: Andy Lutomirski <luto@amacapital.net>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Commit 6a328d8c6f changed the update
logic for the socket but it does not update the SCM_RIGHTS update
as well. This patch is based on the net_prio fix commit
48a87cc26c
net: netprio: fd passed in SCM_RIGHTS datagram not set correctly
A socket fd passed in a SCM_RIGHTS datagram was not getting
updated with the new tasks cgrp prioidx. This leaves IO on
the socket tagged with the old tasks priority.
To fix this add a check in the scm recvmsg path to update the
sock cgrp prioidx with the new tasks value.
Let's apply the same fix for net_cls.
Signed-off-by: Daniel Wagner <daniel.wagner@bmw-carit.de>
Reported-by: Li Zefan <lizefan@huawei.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: John Fastabend <john.r.fastabend@intel.com>
Cc: Neil Horman <nhorman@tuxdriver.com>
Cc: netdev@vger.kernel.org
Cc: cgroups@vger.kernel.org
Signed-off-by: David S. Miller <davem@davemloft.net>
If the user calling sendmsg has the appropriate privieleges
in their user namespace allow them to set the uid, gid, and
pid in the SCM_CREDENTIALS control message to any valid value.
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Pull vfs update from Al Viro:
- big one - consolidation of descriptor-related logics; almost all of
that is moved to fs/file.c
(BTW, I'm seriously tempted to rename the result to fd.c. As it is,
we have a situation when file_table.c is about handling of struct
file and file.c is about handling of descriptor tables; the reasons
are historical - file_table.c used to be about a static array of
struct file we used to have way back).
A lot of stray ends got cleaned up and converted to saner primitives,
disgusting mess in android/binder.c is still disgusting, but at least
doesn't poke so much in descriptor table guts anymore. A bunch of
relatively minor races got fixed in process, plus an ext4 struct file
leak.
- related thing - fget_light() partially unuglified; see fdget() in
there (and yes, it generates the code as good as we used to have).
- also related - bits of Cyrill's procfs stuff that got entangled into
that work; _not_ all of it, just the initial move to fs/proc/fd.c and
switch of fdinfo to seq_file.
- Alex's fs/coredump.c spiltoff - the same story, had been easier to
take that commit than mess with conflicts. The rest is a separate
pile, this was just a mechanical code movement.
- a few misc patches all over the place. Not all for this cycle,
there'll be more (and quite a few currently sit in akpm's tree)."
Fix up trivial conflicts in the android binder driver, and some fairly
simple conflicts due to two different changes to the sock_alloc_file()
interface ("take descriptor handling from sock_alloc_file() to callers"
vs "net: Providing protocol type via system.sockprotoname xattr of
/proc/PID/fd entries" adding a dentry name to the socket)
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: (72 commits)
MAX_LFS_FILESIZE should be a loff_t
compat: fs: Generic compat_sys_sendfile implementation
fs: push rcu_barrier() from deactivate_locked_super() to filesystems
btrfs: reada_extent doesn't need kref for refcount
coredump: move core dump functionality into its own file
coredump: prevent double-free on an error path in core dumper
usb/gadget: fix misannotations
fcntl: fix misannotations
ceph: don't abuse d_delete() on failure exits
hypfs: ->d_parent is never NULL or negative
vfs: delete surplus inode NULL check
switch simple cases of fget_light to fdget
new helpers: fdget()/fdput()
switch o2hb_region_dev_write() to fget_light()
proc_map_files_readdir(): don't bother with grabbing files
make get_file() return its argument
vhost_set_vring(): turn pollstart/pollstop into bool
switch prctl_set_mm_exe_file() to fget_light()
switch xfs_find_handle() to fget_light()
switch xfs_swapext() to fget_light()
...
Passing uids and gids on NETLINK_CB from a process in one user
namespace to a process in another user namespace can result in the
wrong uid or gid being presented to userspace. Avoid that problem by
passing kuids and kgids instead.
- define struct scm_creds for use in scm_cookie and netlink_skb_parms
that holds uid and gid information in kuid_t and kgid_t.
- Modify scm_set_cred to fill out scm_creds by heand instead of using
cred_to_ucred to fill out struct ucred. This conversion ensures
userspace does not get incorrect uid or gid values to look at.
- Modify scm_recv to convert from struct scm_creds to struct ucred
before copying credential values to userspace.
- Modify __scm_send to populate struct scm_creds on in the scm_cookie,
instead of just copying struct ucred from userspace.
- Modify netlink_sendmsg to copy scm_creds instead of struct ucred
into the NETLINK_CB.
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This is an initial merge in of Eric Biederman's work to start adding
user namespace support to the networking.
Signed-off-by: David S. Miller <davem@davemloft.net>
A socket fd passed in a SCM_RIGHTS datagram was not getting
updated with the new tasks cgrp prioidx. This leaves IO on
the socket tagged with the old tasks priority.
To fix this add a check in the scm recvmsg path to update the
sock cgrp prioidx with the new tasks value.
Thanks to Al Viro for catching this.
CC: Neil Horman <nhorman@tuxdriver.com>
Reported-by: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: John Fastabend <john.r.fastabend@intel.com>
Acked-by: Neil Horman <nhorman@tuxdriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
With the existence of kuid_t and kgid_t we can take this further
and remove the usage of struct cred altogether, ensuring we
don't get cache line misses from reference counts. For now
however start simply and do a straight forward conversion
I can be certain is correct.
In cred_to_ucred use from_kuid_munged and from_kgid_munged
as these values are going directly to userspace and we want to use
the userspace safe values not -1 when reporting a value that does not
map. The earlier conversion that used from_kuid was buggy in that
respect. Oops.
Cc: Eric Dumazet <eric.dumazet@gmail.com>
Acked-by: David S. Miller <davem@davemloft.net>
Acked-by: Serge Hallyn <serge.hallyn@canonical.com>
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Remove all #inclusions of asm/system.h preparatory to splitting and killing
it. Performed with the following command:
perl -p -i -e 's!^#\s*include\s*<asm/system[.]h>.*\n!!' `grep -Irl '^#\s*include\s*<asm/system[.]h>' *`
Signed-off-by: David Howells <dhowells@redhat.com>
Since commit 7361c36c52 (af_unix: Allow credentials to work across
user and pid namespaces) af_unix performance dropped a lot.
This is because we now take a reference on pid and cred in each write(),
and release them in read(), usually done from another process,
eventually from another cpu. This triggers false sharing.
# Events: 154K cycles
#
# Overhead Command Shared Object Symbol
# ........ ....... .................. .........................
#
10.40% hackbench [kernel.kallsyms] [k] put_pid
8.60% hackbench [kernel.kallsyms] [k] unix_stream_recvmsg
7.87% hackbench [kernel.kallsyms] [k] unix_stream_sendmsg
6.11% hackbench [kernel.kallsyms] [k] do_raw_spin_lock
4.95% hackbench [kernel.kallsyms] [k] unix_scm_to_skb
4.87% hackbench [kernel.kallsyms] [k] pid_nr_ns
4.34% hackbench [kernel.kallsyms] [k] cred_to_ucred
2.39% hackbench [kernel.kallsyms] [k] unix_destruct_scm
2.24% hackbench [kernel.kallsyms] [k] sub_preempt_count
1.75% hackbench [kernel.kallsyms] [k] fget_light
1.51% hackbench [kernel.kallsyms] [k]
__mutex_lock_interruptible_slowpath
1.42% hackbench [kernel.kallsyms] [k] sock_alloc_send_pskb
This patch includes SCM_CREDENTIALS information in a af_unix message/skb
only if requested by the sender, [man 7 unix for details how to include
ancillary data using sendmsg() system call]
Note: This might break buggy applications that expected SCM_CREDENTIAL
from an unaware write() system call, and receiver not using SO_PASSCRED
socket option.
If SOCK_PASSCRED is set on source or destination socket, we still
include credentials for mere write() syscalls.
Performance boost in hackbench : more than 50% gain on a 16 thread
machine (2 quad-core cpus, 2 threads per core)
hackbench 20 thread 2000
4.228 sec instead of 9.102 sec
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Acked-by: Tim Chen <tim.c.chen@linux.intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Kuniyuki Iwashima