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

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Submitter Brad Figg
Date July 11, 2012, 8:05 p.m.
Message ID <1342037101-25923-2-git-send-email-brad.figg@canonical.com>
Download mbox | patch
Permalink /patch/170508/
State New
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Brad Figg - July 11, 2012, 8:05 p.m.
From: Jason Baron <jbaron@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@redhat.com>
Reported-by: Yurij M. Plotnikov <Yurij.Plotnikov@oktetlabs.ru>
Cc: Nelson Elhage <nelhage@nelhage.com>
Cc: Davide Libenzi <davidel@xmailserver.org>
Tested-by: Alexandra N. Kossovsky <Alexandra.Kossovsky@oktetlabs.ru>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
(cherry picked from commit 13d518074a952d33d47c428419693f63389547e9)
Signed-off-by: Brad Figg <brad.figg@canonical.com>
---
 fs/eventpoll.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

Patch

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);
 	}