Nicolas Iooss <nicolas.iooss_linux@xxxxxxx> wrote:
> 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>
Looks good to me. Tested without regressions on several of my
(non-EPOLLWAKEUP) projects. Adding a few more folks to the Cc: list.
Acked-by: Eric Wong <normalperson@xxxxxxxx>
> ---
> fs/eventpoll.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/fs/eventpoll.c b/fs/eventpoll.c
> index b10b48c..7bcfff9 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
> --
> 1.7.10.4
--
To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
