Null pointer deref with hrtimer_try_to_cancel()

Impact: Prevent kernel crash with posix timer clockid CLOCK_MONOTONIC_RAW commit 2d42244ae71d6c7b0884b5664cf2eda30fb2ae68 (clocksource: introduce CLOCK_MONOTONIC_RAW) introduced a new clockid, which is only available to read out the raw not NTP adjusted system time. The above commit did not prevent that a posix timer can be created with that clockid. The timer_create() syscall succeeds and initializes the timer to a non existing hrtimer base. When the timer is deleted either by timer_delete() or by the exit() cleanup the kernel crashes. Prevent the creation of timers for CLOCK_MONOTONIC_RAW by setting the posix clock function to no_timer_create which returns an error code. Reported-and-tested-by: Eric Sesterhenn <snakebyte@gmx.de> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: Oleg Nesterov <oleg@redhat.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Null pointer deref with hrtimer_try_to_cancel()
Impact: Prevent kernel crash with posix timer clockid CLOCK_MONOTONIC_RAW commit 2d42244ae71d6c7b0884b5664cf2eda30fb2ae68 (clocksource: introduce CLOCK_MONOTONIC_RAW) introduced a new clockid, which is only available to read out the raw not NTP adjusted system time. The above commit did not prevent that a posix timer can be created with that clockid. The timer_create() syscall succeeds and initializes the timer to a non existing hrtimer base. When the timer is deleted either by timer_delete() or by the exit() cleanup the kernel crashes. Prevent the creation of timers for CLOCK_MONOTONIC_RAW by setting the posix clock function to no_timer_create which returns an error code. Reported-and-tested-by: Eric Sesterhenn <snakebyte@gmx.de> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: Oleg Nesterov <oleg@redhat.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Thomas Gleixner · Linus Torvalds
1 parent ab65387243
Showing 1 changed file with 6 additions and 0 deletions Side-by-side Diff
kernel/posix-timers.c
@@ -197,6 +197,11 @@
 	return 0;
 }
  
+static int no_timer_create(struct k_itimer *new_timer)
+{
+	return -EOPNOTSUPP;
+}
+
 /*
  * Return nonzero if we know a priori this clockid_t value is bogus.
  */
@@ -248,6 +253,7 @@
 		.clock_getres = hrtimer_get_res,
 		.clock_get = posix_get_monotonic_raw,
 		.clock_set = do_posix_clock_nosettime,
+		.timer_create = no_timer_create,
 	};
  
 	register_posix_clock(CLOCK_REALTIME, &clock_realtime);
...	...	@@ -197,6 +197,11 @@
197	197	return 0;
198	198	}
199	199
	200	+static int no_timer_create(struct k_itimer *new_timer)
	201	+{
	202	+ return -EOPNOTSUPP;
	203	+}
	204	+
200	205	/*
201	206	* Return nonzero if we know a priori this clockid_t value is bogus.
202	207	*/
...	...	@@ -248,6 +253,7 @@
248	253	.clock_getres = hrtimer_get_res,
249	254	.clock_get = posix_get_monotonic_raw,
250	255	.clock_set = do_posix_clock_nosettime,
	256	+ .timer_create = no_timer_create,
251	257	};
252	258
253	259	register_posix_clock(CLOCK_REALTIME, &clock_realtime);