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    Subject[PATCH 4.19 092/211] posix-cpu-timers: Sanitize bogus WARNONS
    Date
    From: Thomas Gleixner <tglx@linutronix.de>

    [ Upstream commit 692117c1f7a6770ed41dd8f277cd9fed1dfb16f1 ]

    Warning when p == NULL and then proceeding and dereferencing p does not
    make any sense as the kernel will crash with a NULL pointer dereference
    right away.

    Bailing out when p == NULL and returning an error code does not cure the
    underlying problem which caused p to be NULL. Though it might allow to
    do proper debugging.

    Same applies to the clock id check in set_process_cpu_timer().

    Clean them up and make them return without trying to do further damage.

    Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
    Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
    Link: https://lkml.kernel.org/r/20190819143801.846497772@linutronix.de
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    kernel/time/posix-cpu-timers.c | 20 +++++++++++++-------
    1 file changed, 13 insertions(+), 7 deletions(-)

    diff --git a/kernel/time/posix-cpu-timers.c b/kernel/time/posix-cpu-timers.c
    index 76801b9b481eb..d62d7ae5201c5 100644
    --- a/kernel/time/posix-cpu-timers.c
    +++ b/kernel/time/posix-cpu-timers.c
    @@ -375,7 +375,8 @@ static int posix_cpu_timer_del(struct k_itimer *timer)
    struct sighand_struct *sighand;
    struct task_struct *p = timer->it.cpu.task;

    - WARN_ON_ONCE(p == NULL);
    + if (WARN_ON_ONCE(!p))
    + return -EINVAL;

    /*
    * Protect against sighand release/switch in exit/exec and process/
    @@ -580,7 +581,8 @@ static int posix_cpu_timer_set(struct k_itimer *timer, int timer_flags,
    u64 old_expires, new_expires, old_incr, val;
    int ret;

    - WARN_ON_ONCE(p == NULL);
    + if (WARN_ON_ONCE(!p))
    + return -EINVAL;

    /*
    * Use the to_ktime conversion because that clamps the maximum
    @@ -716,10 +718,11 @@ static int posix_cpu_timer_set(struct k_itimer *timer, int timer_flags,

    static void posix_cpu_timer_get(struct k_itimer *timer, struct itimerspec64 *itp)
    {
    - u64 now;
    struct task_struct *p = timer->it.cpu.task;
    + u64 now;

    - WARN_ON_ONCE(p == NULL);
    + if (WARN_ON_ONCE(!p))
    + return;

    /*
    * Easy part: convert the reload time.
    @@ -1004,12 +1007,13 @@ static void check_process_timers(struct task_struct *tsk,
    */
    static void posix_cpu_timer_rearm(struct k_itimer *timer)
    {
    + struct task_struct *p = timer->it.cpu.task;
    struct sighand_struct *sighand;
    unsigned long flags;
    - struct task_struct *p = timer->it.cpu.task;
    u64 now;

    - WARN_ON_ONCE(p == NULL);
    + if (WARN_ON_ONCE(!p))
    + return;

    /*
    * Fetch the current sample and update the timer's expiry time.
    @@ -1206,7 +1210,9 @@ void set_process_cpu_timer(struct task_struct *tsk, unsigned int clock_idx,
    u64 now;
    int ret;

    - WARN_ON_ONCE(clock_idx == CPUCLOCK_SCHED);
    + if (WARN_ON_ONCE(clock_idx >= CPUCLOCK_SCHED))
    + return;
    +
    ret = cpu_timer_sample_group(clock_idx, tsk, &now);

    if (oldval && ret != -EINVAL) {
    --
    2.20.1


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