This is a note to let you know that I've just added the patch titled
epoll: fix use-after-free in eventpoll_release_file
to the 3.15-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
epoll-fix-use-after-free-in-eventpoll_release_file.patch
and it can be found in the queue-3.15 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From ebe06187bf2aec10d537ce4595e416035367d703 Mon Sep 17 00:00:00 2001
From: Konstantin Khlebnikov <koct9i@xxxxxxxxx>
Date: Tue, 17 Jun 2014 06:58:05 +0400
Subject: epoll: fix use-after-free in eventpoll_release_file
From: Konstantin Khlebnikov <koct9i@xxxxxxxxx>
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@xxxxxxxxx>
Reported-by: Cyrill Gorcunov <gorcunov@xxxxxxxxxx>
Cc: Sasha Levin <sasha.levin@xxxxxxxxxx>
Cc: Jason Baron <jbaron@xxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
fs/eventpoll.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
--- a/fs/eventpoll.c
+++ b/fs/eventpoll.c
@@ -910,7 +910,7 @@ static const struct file_operations even
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
* 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);
Patches currently in stable-queue which might be from koct9i@xxxxxxxxx are
queue-3.15/epoll-fix-use-after-free-in-eventpoll_release_file.patch
queue-3.15/tools-vm-page-types.c-catch-sigbus-if-raced-with-truncate.patch
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