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

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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@xxxxxxxxxx>

The patch is

Reviewed-by: Felix Kuehling <Felix.Kuehling@xxxxxxx>

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;



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