[PATCH 3.13 050/163] eventpoll: fix uninitialized variable in epoll_ctl

[Kamal Mostafa]

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

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

From: Nicolas Iooss <nicolas.iooss_linux@xxxxxxx>

commit c680e41b3a2e944185c74bf60531e3d316d3ecc4 upstream.

When calling epoll_ctl with operation EPOLL_CTL_DEL, structure epds is
not initialized but ep_take_care_of_epollwakeup reads its event field.
When this unintialized field has EPOLLWAKEUP bit set, a capability check
is done for CAP_BLOCK_SUSPEND in ep_take_care_of_epollwakeup.  This
produces unexpected messages in the audit log, such as (on a system
running SELinux):

    type=AVC msg=audit(1408212798.866:410): avc:  denied
    { block_suspend } for  pid=7754 comm="dbus-daemon" capability=36
    scontext=unconfined_u:unconfined_r:unconfined_t
    tcontext=unconfined_u:unconfined_r:unconfined_t
    tclass=capability2 permissive=1

    type=SYSCALL msg=audit(1408212798.866:410): arch=c000003e syscall=233
    success=yes exit=0 a0=3 a1=2 a2=9 a3=7fffd4d66ec0 items=0 ppid=1
    pid=7754 auid=1000 uid=0 gid=0 euid=0 suid=0 fsuid=0 egid=0 sgid=0
    fsgid=0 tty=(none) ses=3 comm="dbus-daemon"
    exe="/usr/bin/dbus-daemon"
    subj=unconfined_u:unconfined_r:unconfined_t key=(null)

("arch=c000003e syscall=233 a1=2" means "epoll_ctl(op=EPOLL_CTL_DEL)")

Remove use of epds in epoll_ctl when op == EPOLL_CTL_DEL.

Fixes: 4d7e30d98939 ("epoll: Add a flag, EPOLLWAKEUP, to prevent suspend while epoll events are ready")
Signed-off-by: Nicolas Iooss <nicolas.iooss_linux@xxxxxxx>
Cc: Alexander Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: Arve HjÃnnevÃg <arve@xxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Kamal Mostafa <kamal@xxxxxxxxxxxxx>
---
 fs/eventpoll.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/fs/eventpoll.c b/fs/eventpoll.c
index ead0046..f50d79e 100644
--- a/fs/eventpoll.c
+++ b/fs/eventpoll.c
@@ -1852,7 +1852,8 @@ SYSCALL_DEFINE4(epoll_ctl, int, epfd, int, op, int, fd,
 		goto error_tgt_fput;
 
 	/* Check if EPOLLWAKEUP is allowed */
-	ep_take_care_of_epollwakeup(&epds);
+	if (ep_op_has_event(op))
+		ep_take_care_of_epollwakeup(&epds);
 
 	/*
 	 * We have to check that the file structure underneath the file descriptor
-- 
1.9.1

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/