[PATCH] drm/amdkfd: potential NULL dereference in kfd_set/reset_event()

[Felix Kuehling]

Am 2022-04-13 um 03:36 schrieb Dan Carpenter:
> If lookup_event_by_id() returns a NULL "ev" pointer then the
> spin_lock(&ev->lock) will crash.  This was detected by Smatch:
>
>      drivers/gpu/drm/amd/amdgpu/../amdkfd/kfd_events.c:644 kfd_set_event()
>      error: we previously assumed 'ev' could be null (see line 639)
>
> Fixes: 5273e82c5f47 ("drm/amdkfd: Improve concurrency of event handling")
> Signed-off-by: Dan Carpenter <dan.carpenter at oracle.com>

The patch is

Reviewed-by: Felix Kuehling <Felix.Kuehling at amd.com>

I will apply it to amd-staging-drm-next. Thank you!


> ---
>   drivers/gpu/drm/amd/amdkfd/kfd_events.c | 14 ++++++++++++--
>   1 file changed, 12 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_events.c b/drivers/gpu/drm/amd/amdkfd/kfd_events.c
> index 0fef24b0b915..15570e72a5dd 100644
> --- a/drivers/gpu/drm/amd/amdkfd/kfd_events.c
> +++ b/drivers/gpu/drm/amd/amdkfd/kfd_events.c
> @@ -634,14 +634,19 @@ int kfd_set_event(struct kfd_process *p, uint32_t event_id)
>   	rcu_read_lock();
>   
>   	ev = lookup_event_by_id(p, event_id);
> +	if (!ev) {
> +		ret = -EINVAL;
> +		goto unlock_rcu;
> +	}
>   	spin_lock(&ev->lock);
>   
> -	if (ev && event_can_be_cpu_signaled(ev))
> +	if (event_can_be_cpu_signaled(ev))
>   		set_event(ev);
>   	else
>   		ret = -EINVAL;
>   
>   	spin_unlock(&ev->lock);
> +unlock_rcu:
>   	rcu_read_unlock();
>   	return ret;
>   }
> @@ -660,14 +665,19 @@ int kfd_reset_event(struct kfd_process *p, uint32_t event_id)
>   	rcu_read_lock();
>   
>   	ev = lookup_event_by_id(p, event_id);
> +	if (!ev) {
> +		ret = -EINVAL;
> +		goto unlock_rcu;
> +	}
>   	spin_lock(&ev->lock);
>   
> -	if (ev && event_can_be_cpu_signaled(ev))
> +	if (event_can_be_cpu_signaled(ev))
>   		reset_event(ev);
>   	else
>   		ret = -EINVAL;
>   
>   	spin_unlock(&ev->lock);
> +unlock_rcu:
>   	rcu_read_unlock();
>   	return ret;
>