diff options
| author | Oleg Nesterov <oleg@redhat.com> | 2017-09-01 18:55:33 +0200 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2017-09-07 08:35:41 +0200 |
| commit | d325f1f1e245f3fc19fa4008018a19d224328a63 (patch) | |
| tree | a0b80468bb76c1fe9228684f13f3f71ac31ce437 /lib | |
| parent | dd2342ad66659e759da0cba023fb13acb4b27406 (diff) | |
epoll: fix race between ep_poll_callback(POLLFREE) and ep_free()/ep_remove()
commit 138e4ad67afd5c6c318b056b4d17c17f2c0ca5c0 upstream.
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>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'lib')
0 files changed, 0 insertions, 0 deletions