[PATCH 1/1] [ONEIRIC] [PRECISE] [CVE-2012-3375] epoll: clear the tfile_check_list on -ELOOP

[Brad Figg]

From: Jason Baron <jbaron at redhat.com>

CVE-2012-3375

BugLink: http://bugs.launchpad.net/bugs/1021811

An epoll_ctl(,EPOLL_CTL_ADD,,) operation can return '-ELOOP' to prevent
circular epoll dependencies from being created.  However, in that case we
do not properly clear the 'tfile_check_list'.  Thus, add a call to
clear_tfile_check_list() for the -ELOOP case.

Signed-off-by: Jason Baron <jbaron at redhat.com>
Reported-by: Yurij M. Plotnikov <Yurij.Plotnikov at oktetlabs.ru>
Cc: Nelson Elhage <nelhage at nelhage.com>
Cc: Davide Libenzi <davidel at xmailserver.org>
Tested-by: Alexandra N. Kossovsky <Alexandra.Kossovsky at oktetlabs.ru>
Signed-off-by: Andrew Morton <akpm at linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds at linux-foundation.org>
(cherry picked from commit 13d518074a952d33d47c428419693f63389547e9)
Signed-off-by: Brad Figg <brad.figg at canonical.com>
---
 fs/eventpoll.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/fs/eventpoll.c b/fs/eventpoll.c
index 4d9d3a4..a6f3763 100644
--- a/fs/eventpoll.c
+++ b/fs/eventpoll.c
@@ -1629,8 +1629,10 @@ SYSCALL_DEFINE4(epoll_ctl, int, epfd, int, op, int, fd,
 	if (op == EPOLL_CTL_ADD) {
 		if (is_file_epoll(tfile)) {
 			error = -ELOOP;
-			if (ep_loop_check(ep, tfile) != 0)
+			if (ep_loop_check(ep, tfile) != 0) {
+				clear_tfile_check_list();
 				goto error_tgt_fput;
+			}
 		} else
 			list_add(&tfile->f_tfile_llink, &tfile_check_list);
 	}
-- 
1.7.9.5