[PATCH 6.12 474/567] drm/ttm: Avoid NULL pointer deref for evicted BOs

Greg Kroah-Hartman
2026-01-06T17:40:26Z

From: Simon Richter <Simon.Richter@hogyros.de>

commit 491adc6a0f9903c32b05f284df1148de39e8e644 upstream.

It is possible for a BO to exist that is not currently associated with a
resource, e.g. because it has been evicted.

When devcoredump tries to read the contents of all BOs for dumping, we need
to expect this as well -- in this case, ENODATA is recorded instead of the
buffer contents.

Fixes: 7d08df5d0bd3 ("drm/ttm: Add ttm_bo_access")
Fixes: 09ac4fcb3f25 ("drm/ttm: Implement vm_operations_struct.access v2")
Cc: stable <stable@kernel.org>
Closes: https://gitlab.freedesktop.org/drm/xe/kernel/-/issues/6271
Signed-off-by: Simon Richter <Simon.Richter@hogyros.de>
Reviewed-by: Matthew Brost <matthew.brost@intel.com>
Reviewed-by: Shuicheng Lin <shuicheng.lin@intel.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Matthew Brost <matthew.brost@intel.com>
Link: https://patch.msgid.link/20251013161241.709916-1-Simon.Richter@hogyros.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/gpu/drm/ttm/ttm_bo_vm.c | 6 ++++++
1 file changed, 6 insertions(+)

--- a/drivers/gpu/drm/ttm/ttm_bo_vm.c
+++ b/drivers/gpu/drm/ttm/ttm_bo_vm.c
@@ -421,6 +421,11 @@ int ttm_bo_vm_access(struct vm_area_stru
if (ret)
return ret;

+ if (!bo->resource) {
+ ret = -ENODATA;
+ goto unlock;
+ }
+
switch (bo->resource->mem_type) {
case TTM_PL_SYSTEM:
fallthrough;
@@ -435,6 +440,7 @@ int ttm_bo_vm_access(struct vm_area_stru
ret = -EIO;
}

+unlock:
ttm_bo_unreserve(bo);

return ret;