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authorNicolai Hähnle <nicolai.haehnle@amd.com>2017-02-18 22:59:56 +0100
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2017-05-14 13:32:59 +0200
commit60e3f5a916dc163753df31d0560b42f2d7a6958c (patch)
tree905ebadd794c90a68d45bfb020e1e72f18278553
parent4edbdf57bc26a126aa3cbafd63fae4b00e002e2d (diff)
drm/ttm: fix use-after-free races in vm fault handling
commit 3089c1df10e2931b1d72d2ffa7d86431084c86b3 upstream. 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> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-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 8fb7213277cc..b75391495778 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) ttm_bo_wait(bo, false, true, false);
+ ttm_bo_unreserve(bo);
+ ttm_bo_unref(&bo);
goto out_unlock;
}
@@ -114,8 +117,10 @@ 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;
@@ -160,6 +165,13 @@ 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;
}