drm/ttm: Avoid NULL pointer deref for evicted BOs

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>

diff --git a/drivers/gpu/drm/ttm/ttm_bo_vm.c b/drivers/gpu/drm/ttm/ttm_bo_vm.c
index 4212b8c91dd425d4c94e53ba5e8d2b01410e03d4..d69d71ed7dd99d1f86cfe2036e41dcfdf31d7ee0 100644 (file)
--- 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_struct *vma, unsigned long addr,
        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_struct *vma, unsigned long addr,
                        ret = -EIO;
        }
 
+unlock:
        ttm_bo_unreserve(bo);
 
        return ret;