From cb8d50dfb341e9615c8d203a3e6513dae9ff901d Mon Sep 17 00:00:00 2001 From: Tvrtko Ursulin Date: Tue, 17 Oct 2017 16:09:08 +0100 Subject: [PATCH] drm/i915: Fixup userptr mmu notifier registration error handling 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 Reported-by: Dan Carpenter Fixes: 7741b547b6e0 ("drm/i915: Preallocate our mmu notifier workequeu to unbreak cpu hotplug deadlock") Cc: Dan Carpenter Cc: Chris Wilson Cc: Tvrtko Ursulin Cc: Joonas Lahtinen Reviewed-by: Chris Wilson Link: https://patchwork.freedesktop.org/patch/msgid/20171017150908.12840-1-tvrtko.ursulin@linux.intel.com --- 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 cdc9be7..e26b231 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); } -- 2.7.4