From c680e41b3a2e944185c74bf60531e3d316d3ecc4 Mon Sep 17 00:00:00 2001 From: Nicolas Iooss Date: Tue, 9 Sep 2014 14:50:51 -0700 Subject: [PATCH] eventpoll: fix uninitialized variable in epoll_ctl MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit 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 Cc: Alexander Viro Cc: Arve Hjønnevåg Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- fs/eventpoll.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/fs/eventpoll.c b/fs/eventpoll.c index b10b48c2a7af..7bcfff900f05 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 -- 2.20.1