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syzbot reported use-after-free in mptcp_schedule_work() [1]
Issue here is that mptcp_schedule_work() schedules a work,
then gets a refcount on sk->sk_refcnt if the work was scheduled.
This refcount will be released by mptcp_worker().
[A] if (schedule_work(...)) {
[B] sock_hold(sk);
return true;
}
Problem is that mptcp_worker() can run immediately and complete before [B]
We need instead :
sock_hold(sk);
if (schedule_work(...))
return true;
sock_put(sk);
[1]
refcount_t: addition on 0; use-after-free.
WARNING: CPU: 1 PID: 29 at lib/refcount.c:25 refcount_warn_saturate+0xfa/0x1d0 lib/refcount.c:25
Call Trace:
<TASK>
__refcount_add include/linux/refcount.h:-1 [inline]
__refcount_inc include/linux/refcount.h:366 [inline]
refcount_inc include/linux/refcount.h:383 [inline]
sock_hold include/net/sock.h:816 [inline]
mptcp_schedule_work+0x164/0x1a0 net/mptcp/protocol.c:943
mptcp_tout_timer+0x21/0xa0 net/mptcp/protocol.c:2316
call_timer_fn+0x17e/0x5f0 kernel/time/timer.c:1747
expire_timers kernel/time/timer.c:1798 [inline]
__run_timers kernel/time/timer.c:2372 [inline]
__run_timer_base+0x648/0x970 kernel/time/timer.c:2384
run_timer_base kernel/time/timer.c:2393 [inline]
run_timer_softirq+0xb7/0x180 kernel/time/timer.c:2403
handle_softirqs+0x22f/0x710 kernel/softirq.c:622
__do_softirq kernel/softirq.c:656 [inline]
run_ktimerd+0xcf/0x190 kernel/softirq.c:1138
smpboot_thread_fn+0x542/0xa60 kernel/smpboot.c:160
kthread+0x711/0x8a0 kernel/kthread.c:463
ret_from_fork+0x4bc/0x870 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
Cc: stable@vger.kernel.org
Fixes: 3b1d6210a957 ("mptcp: implement and use MPTCP-level retransmission")
Reported-by: syzbot+355158e7e301548a1424@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/netdev/6915b46f.050a0220.3565dc.0028.GAE@google.com/T/#u
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Link: https://patch.msgid.link/20251113103924.3737425-1-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Linux kernel
============
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In order to build the documentation, use ``make htmldocs`` or
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There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.