Commit 3d44cc3e authored Dec 20, 2008 by Thomas Gleixner Committed by Linus Torvalds Dec 20, 2008

Null pointer deref with hrtimer_try_to_cancel()



Impact: Prevent kernel crash with posix timer clockid CLOCK_MONOTONIC_RAW

commit 2d42244a (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>

parent ab653872

kernel/posix-timers.c

+6 −0

Original line number	Original line	Diff line number	Diff line
	@@ -197,6 +197,11 @@ static int common_timer_create(struct k_itimer *new_timer)
	return 0;		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.		* Return nonzero if we know a priori this clockid_t value is bogus.
	*/		*/
	@@ -248,6 +253,7 @@ static __init int init_posix_timers(void)
	.clock_getres = hrtimer_get_res,		.clock_getres = hrtimer_get_res,
	.clock_get = posix_get_monotonic_raw,		.clock_get = posix_get_monotonic_raw,
	.clock_set = do_posix_clock_nosettime,		.clock_set = do_posix_clock_nosettime,
			.timer_create = no_timer_create,
	};		};

	register_posix_clock(CLOCK_REALTIME, &clock_realtime);		register_posix_clock(CLOCK_REALTIME, &clock_realtime);

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