Re: [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.carpen...@oracle.com>

The patch is

Reviewed-by: Felix Kuehling <felix.kuehl...@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;