epoll: fix use-after-free in eventpoll_release_file
This fixes use-after-free of epi->fllink.next inside list loop macro.
This loop actually releases elements in the body. The list is
rcu-protected but here we cannot hold rcu_read_lock because we need to
lock mutex inside.
The obvious solution is to use list_for_each_entry_safe(). RCU-ness
isn't essential because nobody can change this list under us, it's final
fput for this file.
The bug was introduced by ae10b2b4eb01 ("epoll: optimize EPOLL_CTL_DEL
using rcu")
Signed-off-by: Konstantin Khlebnikov <[email protected]>
Reported-by: Cyrill Gorcunov <[email protected]>
Cc: Stable <[email protected]> # 3.13+
Cc: Sasha Levin <[email protected]>
Cc: Jason Baron <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
1 file changed
