linux-kernel - [ 023/108] epoll: clear the tfile_check

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Message-Id: <20120723010655.027064805@decadent.org.uk>
Date:	Mon, 23 Jul 2012 02:07:14 +0100
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	torvalds@...ux-foundation.org, akpm@...ux-foundation.org,
	alan@...rguk.ukuu.org.uk, Jason Baron <jbaron@...hat.com>,
	"Yurij M. Plotnikov" <Yurij.Plotnikov@...etlabs.ru>,
	Nelson Elhage <nelhage@...hage.com>,
	Davide Libenzi <davidel@...ilserver.org>,
	"Alexandra N. Kossovsky" <Alexandra.Kossovsky@...etlabs.ru>
Subject: [ 023/108] epoll: clear the tfile_check_list on -ELOOP

3.2-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Jason Baron <jbaron@...hat.com>

commit 13d518074a952d33d47c428419693f63389547e9 upstream.

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@...hat.com>
Reported-by: Yurij M. Plotnikov <Yurij.Plotnikov@...etlabs.ru>
Cc: Nelson Elhage <nelhage@...hage.com>
Cc: Davide Libenzi <davidel@...ilserver.org>
Tested-by: Alexandra N. Kossovsky <Alexandra.Kossovsky@...etlabs.ru>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 fs/eventpoll.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

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);
 	}


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