linux-kernel - [PATCH] epoll: clear the tfile_check

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Message-Id: <201204171434.q3HEYqrq007242@int-mx09.intmail.prod.int.phx2.redhat.com>
Date:	Tue, 17 Apr 2012 10:34:52 -0400
From:	Jason Baron <jbaron@...hat.com>
To:	akpm@...ux-foundation.org
Cc:	Yurij.Plotnikov@...etlabs.ru, Alexandra.Kossovsky@...etlabs.ru,
	davidel@...ilserver.org, nelhage@...hage.com,
	linux-kernel@...r.kernel.org
Subject: [PATCH] epoll: clear the tfile_check_list on -ELOOP

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.

Reported-by: Yurij M. Plotnikov <Yurij.Plotnikov@...etlabs.ru>
Tested-by: Alexandra N. Kossovsky <Alexandra.Kossovsky@...etlabs.ru>
Signed-off-by: Jason Baron <jbaron@...hat.com>
---
 fs/eventpoll.c |    4 +++-
 1 files changed, 3 insertions(+), 1 deletions(-)

diff --git a/fs/eventpoll.c b/fs/eventpoll.c
index 739b098..c0b3c70 100644
--- a/fs/eventpoll.c
+++ b/fs/eventpoll.c
@@ -1663,8 +1663,10 @@ 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);
 	}
-- 
1.7.7.6

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