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

[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.carpen...@oracle.com>
---
 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;
 
-- 
2.20.1