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authorKonstantin Khlebnikov <koct9i@gmail.com>2014-06-17 06:58:05 +0400
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2014-06-30 20:14:04 -0700
commitfaf067b39a509e17682b6276cc54012b67683dc3 (patch)
parenta8e9e3d06557c580665d1ac5a6059cb7b9b4a01e (diff)
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>
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.
- 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);