CVE-2024-35910
Assigner: Linux
Published: 2024-05-19T08:35:03.287Z
State: PUBLISHED
descriptions: value: In the Linux kernel, the following vulnerability has been resolved:

tcp: properly terminate timers for kernel sockets

We had various syzbot reports about tcp timers firing after
the corresponding netns has been dismantled.

Fortunately Josef Bacik could trigger the issue more often,
and could test a patch I wrote two years ago.

When TCP sockets are closed, we call inet_csk_clear_xmit_timers()
to 'stop' the timers.

inet_csk_clear_xmit_timers() can be called from any context,
including when socket lock is held.
This is the reason it uses sk_stop_timer(), aka del_timer().
This means that ongoing timers might finish much later.

For user sockets, this is fine because each running timer
holds a reference on the socket, and the user socket holds
a reference on the netns.

For kernel sockets, we risk that the netns is freed before
timer can complete, because kernel sockets do not hold
reference on the netns.

This patch adds inet_csk_clear_xmit_timers_sync() function
that using sk_stop_timer_sync() to make sure all timers
are terminated before the kernel socket is released.
Modules using kernel sockets close them in their netns exit()
handler.

Also add sock_not_owned_by_me() helper to get LOCKDEP
support : inet_csk_clear_xmit_timers_sync() must not be called
while socket lock is held.

It is very possible we can revert in the future commit
3a58f13a881e ("net: rds: acquire refcount on TCP sockets")
which attempted to solve the issue in rds only.
(net/smc/af_smc.c and net/mptcp/subflow.c have similar code)

We probably can remove the check_net() tests from
tcp_out_of_resources() and __tcp_close() in the future.
affected: product: Linux
vendor: Linux
defaultStatus: unaffected
repo: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
versions: version: 8a68173691f0
lessThan: 93f0133b9d58
status: affected
versionType: git
version: 8a68173691f0
lessThan: 44e62f5d3567
status: affected
versionType: git
version: 8a68173691f0
lessThan: e3e27d2b446d
status: affected
versionType: git
version: 8a68173691f0
lessThan: 2e43d8eba6ed
status: affected
versionType: git
version: 8a68173691f0
lessThan: 91b243de910a
status: affected
versionType: git
version: 8a68173691f0
lessThan: c1ae4d1e76ea
status: affected
versionType: git
version: 8a68173691f0
lessThan: 899265c1389f
status: affected
versionType: git
version: 8a68173691f0
lessThan: 151c9c724d05
status: affected
versionType: git
product: Linux
vendor: Linux
defaultStatus: affected
repo: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
versions: version: 4.2
status: affected
version: 0
lessThan: 4.2
status: unaffected
versionType: custom
version: 4.19.312
lessThanOrEqual: 4.19.*
status: unaffected
versionType: custom
version: 5.4.274
lessThanOrEqual: 5.4.*
status: unaffected
versionType: custom
version: 5.10.215
lessThanOrEqual: 5.10.*
status: unaffected
versionType: custom
version: 5.15.154
lessThanOrEqual: 5.15.*
status: unaffected
versionType: custom
version: 6.1.85
lessThanOrEqual: 6.1.*
status: unaffected
versionType: custom
version: 6.6.26
lessThanOrEqual: 6.6.*
status: unaffected
versionType: custom
version: 6.8.5
lessThanOrEqual: 6.8.*
status: unaffected
versionType: custom
version: 6.9
lessThanOrEqual: *
status: unaffected
versionType: original_commit_for_fix
title: tcp: properly terminate timers for kernel sockets
x_generator: engine: bippy-d175d3acf727