This is a note to let you know that I've just added the patch titled

posix-timer: Properly check sigevent->sigev_notify

to the 4.14-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...

The filename of the patch is: posix-timer-properly-check-sigevent-sigev_notify.patch and it can be found in the queue-4.14 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.

From cef31d9af908243421258f1df35a4a644604efbe Mon Sep 17 00:00:00 2001

From: Thomas Gleixner tglx@linutronix.de Date: Fri, 15 Dec 2017 10:32:03 +0100 Subject: posix-timer: Properly check sigevent->sigev_notify

From: Thomas Gleixner tglx@linutronix.de

commit cef31d9af908243421258f1df35a4a644604efbe upstream.

timer_create() specifies via sigevent->sigev_notify the signal delivery for the new timer. The valid modes are SIGEV_NONE, SIGEV_SIGNAL, SIGEV_THREAD and (SIGEV_SIGNAL | SIGEV_THREAD_ID).

The sanity check in good_sigevent() is only checking the valid combination for the SIGEV_THREAD_ID bit, i.e. SIGEV_SIGNAL, but if SIGEV_THREAD_ID is not set it accepts any random value.

This has no real effects on the posix timer and signal delivery code, but it affects show_timer() which handles the output of /proc/$PID/timers. That function uses a string array to pretty print sigev_notify. The access to that array has no bound checks, so random sigev_notify cause access beyond the array bounds.

Add proper checks for the valid notify modes and remove the SIGEV_THREAD_ID masking from various code pathes as SIGEV_NONE can never be set in combination with SIGEV_THREAD_ID.

Reported-by: Eric Biggers ebiggers3@gmail.com Reported-by: Dmitry Vyukov dvyukov@google.com Reported-by: Alexey Dobriyan adobriyan@gmail.com Signed-off-by: Thomas Gleixner tglx@linutronix.de Cc: John Stultz john.stultz@linaro.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org

--- kernel/time/posix-timers.c | 29 +++++++++++++++++------------ 1 file changed, 17 insertions(+), 12 deletions(-)

--- a/kernel/time/posix-timers.c +++ b/kernel/time/posix-timers.c @@ -434,17 +434,22 @@ static struct pid *good_sigevent(sigeven { struct task_struct *rtn = current->group_leader;

- if ((event->sigev_notify & SIGEV_THREAD_ID ) && - (!(rtn = find_task_by_vpid(event->sigev_notify_thread_id)) || - !same_thread_group(rtn, current) || - (event->sigev_notify & ~SIGEV_THREAD_ID) != SIGEV_SIGNAL)) + switch (event->sigev_notify) { + case SIGEV_SIGNAL | SIGEV_THREAD_ID: + rtn = find_task_by_vpid(event->sigev_notify_thread_id); + if (!rtn || !same_thread_group(rtn, current)) + return NULL; + /* FALLTHRU */ + case SIGEV_SIGNAL: + case SIGEV_THREAD: + if (event->sigev_signo <= 0 || event->sigev_signo > SIGRTMAX) + return NULL; + /* FALLTHRU */ + case SIGEV_NONE: + return task_pid(rtn); + default: return NULL; - - if (((event->sigev_notify & ~SIGEV_THREAD_ID) != SIGEV_NONE) && - ((event->sigev_signo <= 0) || (event->sigev_signo > SIGRTMAX))) - return NULL; - - return task_pid(rtn); + } }

static struct k_itimer * alloc_posix_timer(void) @@ -669,7 +674,7 @@ void common_timer_get(struct k_itimer *t struct timespec64 ts64; bool sig_none;

- sig_none = (timr->it_sigev_notify & ~SIGEV_THREAD_ID) == SIGEV_NONE; + sig_none = timr->it_sigev_notify == SIGEV_NONE; iv = timr->it_interval;

/* interval timer ? */ @@ -856,7 +861,7 @@ int common_timer_set(struct k_itimer *ti

timr->it_interval = timespec64_to_ktime(new_setting->it_interval); expires = timespec64_to_ktime(new_setting->it_value); - sigev_none = (timr->it_sigev_notify & ~SIGEV_THREAD_ID) == SIGEV_NONE; + sigev_none = timr->it_sigev_notify == SIGEV_NONE;

kc->timer_arm(timr, expires, flags & TIMER_ABSTIME, sigev_none); timr->it_active = !sigev_none;

Patches currently in stable-queue which might be from tglx@linutronix.de are

queue-4.14/sched-rt-do-not-pull-from-current-cpu-if-only-one-cpu-to-pull.patch queue-4.14/x86-boot-compressed-64-print-error-if-5-level-paging-is-not-supported.patch queue-4.14/posix-timer-properly-check-sigevent-sigev_notify.patch queue-4.14/x86-boot-compressed-64-detect-and-handle-5-level-paging-at-boot-time.patch