drm/xe: skip eviction of a BO with no resource

Overview

In the Linux kernel, the following vulnerability has been resolved:

drm/xe: skip eviction of a BO with no resource

xe_evict_flags() switches on tbo->resource->mem_type to choose an eviction placement. An xe BO can reach eviction with no ttm.resource, e.g. an imported dma-buf BO whose resource was freed during teardown while its attachment is still live: the exporter then invalidates it via xe_dma_buf_move_notify() -> xe_bo_evict(), and the switch dereferences a NULL resource and faults.

A BO with no resource has nothing placed or mapped, so there is nothing to evict. Return an empty placement (num_placement = 0), mirroring the handling already used for non-xe scatter-gather BOs just above; ttm_bo_validate() then takes the pipeline-gutting path and returns 0.

Without the fix the xe_dma_buf@xe_test_dmabuf_move_notify_no_resource dynamic live selftest will fail with below stack.

BUG: kernel NULL pointer dereference, address: 0000000000000010 RIP: 0010:xe_evict_flags+0xf4/0x140 [xe] Call Trace: <TASK> xe_bo_evict+0x40/0xa0 [xe] ? ttm_bo_pipeline_gutting+0x71/0x180 [ttm] xe_test_dmabuf_move_notify_no_resource+0x182/0x440 [xe] xe_dma_buf_kunit+0x387/0x580 [xe]

v2: Add Fixes tag and failure info in commit text (Matt Brost)

(cherry picked from commit dbcfaac6331f1fcb0c2fe3ad3e9adb1e5d43ec0c)

Affected

• Linux >= dd08ebf6c3525a7ea2186e636df064ea47281987 < 6046bb9cb2859e3d9bf939e4d6527f3827e1096f
• Linux >= dd08ebf6c3525a7ea2186e636df064ea47281987 < b6499d19ade1f1e4a1e6b739abc8c815297c98b8
• Linux >= dd08ebf6c3525a7ea2186e636df064ea47281987 < 448e76cbdc6652ccd3ba337b7a6e1f028859f2ed
• Linux 6.8

Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.