From 12058077b2e963d16d2d673d46233a7f46add7c9 Mon Sep 17 00:00:00 2001 From: =?utf8?q?Thomas=20Hellstr=C3=B6m?= Date: Mon, 20 Jun 2022 14:36:59 +0200 Subject: [PATCH] drm/i915: Fix vm use-after-free in vma destruction MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit In vma destruction, the following race may occur: Thread 1: Thread 2: i915_vma_destroy(); ... list_del_init(vma->vm_link); ... mutex_unlock(vma->vm->mutex); __i915_vm_release(); release_references(); And in release_reference() we dereference vma->vm to get to the vm gt pointer, leading to a use-after free. However, __i915_vm_release() grabs the vm->mutex so the vm won't be destroyed before vma->vm->mutex is released, so extract the gt pointer under the vm->mutex to avoid the vma->vm dereference in release_references(). v2: Fix a typo in the commit message (Andi Shyti) Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/5944 Fixes: e1a7ab4fca0c ("drm/i915: Remove the vm open count") Cc: Niranjana Vishwanathapura Cc: Matthew Auld Signed-off-by: Thomas Hellström Acked-by: Nirmoy Das Reviewed-by: Andrzej Hajda Reviewed-by: Matthew Auld Link: https://patchwork.freedesktop.org/patch/msgid/20220620123659.381772-1-thomas.hellstrom@linux.intel.com (cherry picked from commit 1926a6b75954fc1a8b44d10bd0c67db957b78cf7) Signed-off-by: Rodrigo Vivi --- drivers/gpu/drm/i915/i915_vma.c | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-) diff --git a/drivers/gpu/drm/i915/i915_vma.c b/drivers/gpu/drm/i915/i915_vma.c index 0bffb70b3c5f..04d12f278f57 100644 --- a/drivers/gpu/drm/i915/i915_vma.c +++ b/drivers/gpu/drm/i915/i915_vma.c @@ -1637,10 +1637,10 @@ static void force_unbind(struct i915_vma *vma) GEM_BUG_ON(drm_mm_node_allocated(&vma->node)); } -static void release_references(struct i915_vma *vma, bool vm_ddestroy) +static void release_references(struct i915_vma *vma, struct intel_gt *gt, + bool vm_ddestroy) { struct drm_i915_gem_object *obj = vma->obj; - struct intel_gt *gt = vma->vm->gt; GEM_BUG_ON(i915_vma_is_active(vma)); @@ -1695,11 +1695,12 @@ void i915_vma_destroy_locked(struct i915_vma *vma) force_unbind(vma); list_del_init(&vma->vm_link); - release_references(vma, false); + release_references(vma, vma->vm->gt, false); } void i915_vma_destroy(struct i915_vma *vma) { + struct intel_gt *gt; bool vm_ddestroy; mutex_lock(&vma->vm->mutex); @@ -1707,8 +1708,11 @@ void i915_vma_destroy(struct i915_vma *vma) list_del_init(&vma->vm_link); vm_ddestroy = vma->vm_ddestroy; vma->vm_ddestroy = false; + + /* vma->vm may be freed when releasing vma->vm->mutex. */ + gt = vma->vm->gt; mutex_unlock(&vma->vm->mutex); - release_references(vma, vm_ddestroy); + release_references(vma, gt, vm_ddestroy); } void i915_vma_parked(struct intel_gt *gt) -- 2.34.1