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authorNicolai Hähnle <nicolai.haehnle@amd.com>2017-02-18 22:59:56 +0100
committerAlex Deucher <alexander.deucher@amd.com>2017-02-21 16:48:45 -0500
commit3089c1df10e2931b1d72d2ffa7d86431084c86b3 (patch)
treedfcf8846b214b4b340ed5eac64cc1810219d4ecb
parentc836fec5ce8eb0d0c08fa0ea5fb71df3290d1601 (diff)
drm/ttm: fix use-after-free races in vm fault handling
The vm fault handler relies on the fact that the VMA owns a reference to the BO. However, once mmap_sem is released, other tasks are free to destroy the VMA, which can lead to the BO being freed. Fix two code paths where that can happen, both related to vm fault retries. Found via a lock debugging warning which flagged &bo->wu_mutex as locked while being destroyed. Fixes: cbe12e74ee4e ("drm/ttm: Allow vm fault retries") Signed-off-by: Nicolai Hähnle <nicolai.haehnle@amd.com> Reviewed-by: Christian König <christian.koenig@amd.com> Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
-rw-r--r--drivers/gpu/drm/ttm/ttm_bo_vm.c12
1 files changed, 12 insertions, 0 deletions
diff --git a/drivers/gpu/drm/ttm/ttm_bo_vm.c b/drivers/gpu/drm/ttm/ttm_bo_vm.c
index 68ef993ab431..88169141bef5 100644
--- a/drivers/gpu/drm/ttm/ttm_bo_vm.c
+++ b/drivers/gpu/drm/ttm/ttm_bo_vm.c
@@ -66,8 +66,11 @@ static int ttm_bo_vm_fault_idle(struct ttm_buffer_object *bo,
if (vmf->flags & FAULT_FLAG_RETRY_NOWAIT)
goto out_unlock;
+ ttm_bo_reference(bo);
up_read(&vma->vm_mm->mmap_sem);
(void) dma_fence_wait(bo->moving, true);
+ ttm_bo_unreserve(bo);
+ ttm_bo_unref(&bo);
goto out_unlock;
}
@@ -120,8 +123,10 @@ static int ttm_bo_vm_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
if (vmf->flags & FAULT_FLAG_ALLOW_RETRY) {
if (!(vmf->flags & FAULT_FLAG_RETRY_NOWAIT)) {
+ ttm_bo_reference(bo);
up_read(&vma->vm_mm->mmap_sem);
(void) ttm_bo_wait_unreserved(bo);
+ ttm_bo_unref(&bo);
}
return VM_FAULT_RETRY;
@@ -166,6 +171,13 @@ static int ttm_bo_vm_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
ret = ttm_bo_vm_fault_idle(bo, vma, vmf);
if (unlikely(ret != 0)) {
retval = ret;
+
+ if (retval == VM_FAULT_RETRY &&
+ !(vmf->flags & FAULT_FLAG_RETRY_NOWAIT)) {
+ /* The BO has already been unreserved. */
+ return retval;
+ }
+
goto out_unlock;
}