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    SubjectRe: [BUG] 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-by: Eric Sesterhenn <>
    Signed-off-by: Thomas Gleixner <>
    diff --git a/kernel/posix-timers.c b/kernel/posix-timers.c
    index 5e79c66..a140e44 100644
    --- a/kernel/posix-timers.c
    +++ b/kernel/posix-timers.c
    @@ -197,6 +197,11 @@ static int common_timer_create(struct k_itimer *new_timer)
    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 @@ static __init int init_posix_timers(void)
    .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);

     \ /
      Last update: 2008-12-20 21:31    [W:0.024 / U:17.252 seconds]
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