sctp: hold asoc or transport before mod_timer() in timer handlers

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Take the association or transport reference before rearming a timer in the
timer handlers.

The existing code calls mod_timer() before taking the reference needed by
the rearmed timer without holding the sock lock. This creates a race with
timer cleanup: if the timer is deleted after mod_timer() returns but before
the reference is taken, the cleanup path can drop the timer's reference and
destroy the transport or association. The timer handler then takes a
reference on the already freed object and eventually drops it, causing a
refcount underflow.

Hold the object before mod_timer() and drop the reference if mod_timer()
reports that the timer was already pending in timer handlers. Apply the
same ordering to the proto-unreachable path, which can rearm a transport
timer outside the timer handlers without holding the sock lock.

Fixes: 1da177e4c3 ("Linux-2.6.12-rc2")
Reported-by: Tangxin Xie <xietangxin@h-partners.com>
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Link: https://patch.msgid.link/c31b5e3ee2b7274e804f5eba2f21e2412e7eef7a.1790013825.git.lucien.xin@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

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This commit is contained in:

Xin Long 2026-09-21 14:03:45 -04:00 • committed by Jakub Kicinski

parent 6836807c5f

commit cae23ae3f7

2 changed files with 26 additions and 18 deletions

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7

net/sctp/input.c

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37

net/sctp/sm_sideeffect.c

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