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author | Oleg Nesterov <oleg@redhat.com> | 2017-09-01 19:55:33 +0300 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2017-09-01 23:07:35 +0300 |
commit | 138e4ad67afd5c6c318b056b4d17c17f2c0ca5c0 (patch) | |
tree | 2d214e233ed80eb887d8a81e11be2613c37d9874 /arch/alpha/boot/stdio.c | |
parent | 8cf9f2a29ff1265a392e5b2461c69a9e53b4539f (diff) | |
download | linux-138e4ad67afd5c6c318b056b4d17c17f2c0ca5c0.tar.xz |
epoll: fix race between ep_poll_callback(POLLFREE) and ep_free()/ep_remove()
The race was introduced by me in commit 971316f0503a ("epoll:
ep_unregister_pollwait() can use the freed pwq->whead"). I did not
realize that nothing can protect eventpoll after ep_poll_callback() sets
->whead = NULL, only whead->lock can save us from the race with
ep_free() or ep_remove().
Move ->whead = NULL to the end of ep_poll_callback() and add the
necessary barriers.
TODO: cleanup the ewake/EPOLLEXCLUSIVE logic, it was confusing even
before this patch.
Hopefully this explains use-after-free reported by syzcaller:
BUG: KASAN: use-after-free in debug_spin_lock_before
...
_raw_spin_lock_irqsave+0x4a/0x60 kernel/locking/spinlock.c:159
ep_poll_callback+0x29f/0xff0 fs/eventpoll.c:1148
this is spin_lock(eventpoll->lock),
...
Freed by task 17774:
...
kfree+0xe8/0x2c0 mm/slub.c:3883
ep_free+0x22c/0x2a0 fs/eventpoll.c:865
Fixes: 971316f0503a ("epoll: ep_unregister_pollwait() can use the freed pwq->whead")
Reported-by: 范龙飞 <long7573@126.com>
Cc: stable@vger.kernel.org
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'arch/alpha/boot/stdio.c')
0 files changed, 0 insertions, 0 deletions