[PATCH AUTOSEL 5.3 109/203] posix-cpu-timers: Sanitize bogus WARNONS

Sasha Levin
2019-09-22T19:34:47Z

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 0a426f4e31251..5bbad147a90cf 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
@@ -715,10 +717,11 @@ 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.
@@ -1000,12 +1003,13 @@ 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.
@@ -1202,7 +1206,9 @@ 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