1. 03 Sep, 2017 16 commits
  2. 02 Sep, 2017 23 commits
  3. 01 Sep, 2017 1 commit
    • Oleg Nesterov's avatar
      epoll: fix race between ep_poll_callback(POLLFREE) and ep_free()/ep_remove() · 138e4ad6
      Oleg Nesterov authored
      The race was introduced by me in commit 971316f0 ("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: 971316f0 ("epoll: ep_unregister_pollwait() can use the freed pwq->whead")
      Reported-by: default avatar范龙飞 <long7573@126.com>
      Cc: stable@vger.kernel.org
      Signed-off-by: default avatarOleg Nesterov <oleg@redhat.com>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      138e4ad6