Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932262AbaF3MT3 (ORCPT ); Mon, 30 Jun 2014 08:19:29 -0400 Received: from ip4-83-240-18-248.cust.nbox.cz ([83.240.18.248]:51940 "EHLO ip4-83-240-18-248.cust.nbox.cz" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753113AbaF3LxZ (ORCPT ); Mon, 30 Jun 2014 07:53:25 -0400 From: Jiri Slaby To: stable@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Konstantin Khlebnikov , Sasha Levin , Jason Baron , Linus Torvalds , Jiri Slaby Subject: [PATCH 3.12 005/181] epoll: fix use-after-free in eventpoll_release_file Date: Mon, 30 Jun 2014 13:50:26 +0200 Message-Id: X-Mailer: git-send-email 2.0.0 In-Reply-To: <61844d8e25eb8899b0836afa9796fa239db80f1f.1404128997.git.jslaby@suse.cz> References: <61844d8e25eb8899b0836afa9796fa239db80f1f.1404128997.git.jslaby@suse.cz> In-Reply-To: References: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Konstantin Khlebnikov 3.12-stable review patch. If anyone has any objections, please let me know. =============== 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 Reported-by: Cyrill Gorcunov Cc: Stable # 3.13+ Cc: Sasha Levin Cc: Jason Baron Signed-off-by: Linus Torvalds Signed-off-by: Jiri Slaby --- fs/eventpoll.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/fs/eventpoll.c b/fs/eventpoll.c index d76c9744c774..55ebb8886014 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); -- 2.0.0 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/