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| author | Konstantin Khlebnikov <koct9i@gmail.com> | 2014-06-17 06:58:05 +0400 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2014-06-30 20:12:02 -0700 |
| commit | b0d3f527adbe90799e10000a0c59e88f0174bfaf (patch) | |
| tree | cfe6fdb21570db8c056c097f936c309ce1d1753f | |
| parent | b83627d417975fa8681344384ac55a1c4751f55f (diff) | |
| download | lwn-b0d3f527adbe90799e10000a0c59e88f0174bfaf.tar.gz lwn-b0d3f527adbe90799e10000a0c59e88f0174bfaf.zip | |
epoll: fix use-after-free in eventpoll_release_file
commit ebe06187bf2aec10d537ce4595e416035367d703 upstream.
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 <koct9i@gmail.com>
Reported-by: Cyrill Gorcunov <gorcunov@openvz.org>
Cc: Sasha Levin <sasha.levin@oracle.com>
Cc: Jason Baron <jbaron@akamai.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | fs/eventpoll.c | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/fs/eventpoll.c b/fs/eventpoll.c index af903128891c..ead00467282d 100644 --- a/fs/eventpoll.c +++ b/fs/eventpoll.c @@ -910,7 +910,7 @@ static const struct file_operations eventpoll_fops = { void eventpoll_release_file(struct file *file) { struct eventpoll *ep; - struct epitem *epi; + struct epitem *epi, *next; /* * We don't want to get "file->f_lock" because it is not @@ -926,7 +926,7 @@ void eventpoll_release_file(struct file *file) * Besides, ep_remove() acquires the lock, so we can't hold it here. */ mutex_lock(&epmutex); - list_for_each_entry_rcu(epi, &file->f_ep_links, fllink) { + list_for_each_entry_safe(epi, next, &file->f_ep_links, fllink) { ep = epi->ep; mutex_lock_nested(&ep->mtx, 0); ep_remove(ep, epi); |