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.

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>

1 files changed, 3 insertions, 1 deletions

diff --git a/fs/eventpoll.c b/fs/eventpoll.c
index 739b0985b398..c0b3c70ee87a 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);
         }