From: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
Avoid dereferencing the error pointer and also avoid returning NULL
from i915_mmu_notifier_find since the callers do not expect that.
Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
Reported-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
Fixes: 7741b547b6e0 ("drm/i915: Preallocate our mmu notifier workequeu to unbreak cpu hotplug deadlock")
Cc: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
Cc: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Cc: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
Cc: Joonas Lahtinen <joonas.lahtinen@xxxxxxxxxxxxxxx>
---
drivers/gpu/drm/i915/i915_gem_userptr.c | 10 ++++++----
1 file changed, 6 insertions(+), 4 deletions(-)
diff --git a/drivers/gpu/drm/i915/i915_gem_userptr.c b/drivers/gpu/drm/i915/i915_gem_userptr.c
index cdc9be799eee..e26b23171b56 100644
--- a/drivers/gpu/drm/i915/i915_gem_userptr.c
+++ b/drivers/gpu/drm/i915/i915_gem_userptr.c
@@ -221,15 +221,17 @@ i915_mmu_notifier_find(struct i915_mm_struct *mm)
/* Protected by mm_lock */
mm->mn = fetch_and_zero(&mn);
}
- } else {
- /* someone else raced and successfully installed the mmu
- * notifier, we can cancel our own errors */
+ } else if (mm->mn) {
+ /*
+ * Someone else raced and successfully installed the mmu
+ * notifier, we can cancel our own errors.
+ */
err = 0;
}
mutex_unlock(&mm->i915->mm_lock);
up_write(&mm->mm->mmap_sem);
- if (mn) {
+ if (mn && !IS_ERR(mn)) {
destroy_workqueue(mn->wq);
kfree(mn);
}
--
2.9.5
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