{"id":"CVE-2026-68266","title":"drm/xe: Hold a dma-buf reference for imported BOs","summary":"In the Linux kernel, the following vulnerability has been resolved:\n\ndrm/xe: Hold a dma-buf reference for imported BOs\n\nAn imported dma-buf BO is created as a ttm_bo_type_sg BO whose\nreservation object is the exporter's dma_buf->resv. Th…","severity":"high","cvss":7.8,"cvssVector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","cvssSource":"cna","vendor":"Linux","product":"Linux","affected":["Linux >= dd08ebf6c3525a7ea2186e636df064ea47281987 < c22d65d62b3318e237c0e5b1177d90ab83d9fe06","Linux >= dd08ebf6c3525a7ea2186e636df064ea47281987 < c1954c66662de477a8f4309335b775f7b07bd28b","Linux >= dd08ebf6c3525a7ea2186e636df064ea47281987 < ba8c4cbb31c6f81fa5b12d6e28f1f706040aff48","Linux >= dd08ebf6c3525a7ea2186e636df064ea47281987 < 62775525a27c3b0d56382e08ba81ee2d322058b6","Linux 6.8"],"ssvc":{"exploitation":"none","automatable":"no","technicalImpact":"total","timestamp":"2026-10-16T15:46:26.487807Z"},"published":"2026-08-10","updated":"2026-10-16","sourceUpdated":"2026-10-16T15:53:05.657Z","source":"CVEORG","sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-68266","references":[{"url":"https://git.kernel.org/stable/c/c22d65d62b3318e237c0e5b1177d90ab83d9fe06"},{"url":"https://git.kernel.org/stable/c/c1954c66662de477a8f4309335b775f7b07bd28b"},{"url":"https://git.kernel.org/stable/c/ba8c4cbb31c6f81fa5b12d6e28f1f706040aff48"},{"url":"https://git.kernel.org/stable/c/62775525a27c3b0d56382e08ba81ee2d322058b6"}],"tags":["cve.org"],"epss":0.00134,"epssPercentile":0.026,"ingestedAt":"2026-10-16T17:24:46.853Z","slug":"CVE-2026-68266","body":"## Overview\n\nIn the Linux kernel, the following vulnerability has been resolved:\n\ndrm/xe: Hold a dma-buf reference for imported BOs\n\nAn imported dma-buf BO is created as a ttm_bo_type_sg BO whose\nreservation object is the exporter's dma_buf->resv. The importer,\nhowever, only takes a dma-buf reference after a successful\ndma_buf_dynamic_attach(). Until then nothing keeps the exporter alive,\nso if the exporter is freed while the BO still references its resv, a\nlater access to that resv is a use-after-free:\n\n  Oops: general protection fault, probably for non-canonical address\n        0x6b6b6b6b6b6b6b9c\n  Workqueue: ttm ttm_bo_delayed_delete [ttm]\n  RIP: 0010:mutex_can_spin_on_owner+0x3f/0xc0\n\nThis can be reached on two paths:\n\n - dma_buf_dynamic_attach() fails, or\n - ttm_bo_init_reserved() fails during BO creation.\n\nIn both cases the BO already has bo->base.resv pointing at the exporter\nresv, and sg BOs are always torn down via ttm_bo_delayed_delete(), which\nlocks bo->base.resv asynchronously - potentially after the exporter has\nbeen freed.\n\nTake the dma-buf reference in xe_bo_init_locked(), before\nttm_bo_init_reserved(), so it also covers a creation failure there, and\nrelease it in xe_ttm_bo_destroy(). The reference is held for the whole\nBO lifetime, keeping the shared resv alive on every path.\n\nv2:\n  - Reworked the fix to avoid creating the imported sg BO before\n    dma_buf_dynamic_attach() succeeds.\n  - Attach with importer_priv == NULL and make invalidate_mappings ignore\n    incomplete imports.\n\nv3:\n  - Dropped the xe-side reordering approach since importer_priv must be\n    valid when dma_buf_dynamic_attach() publishes the attachment.\n  - Per Christian's suggestion on the v1 thread, keyed the check on\n    import_attach rather than removing the sg guard entirely.\n  - Fixes both xe and amdgpu in a single TTM patch.\n\nv4:\n  - Moved import_attach check to after dma_resv_copy_fences() so fences\n    are copied before returning for successful imports (Thomas).\n  - Removed exporter-alive claim from commit message (Thomas).\n\nv5:\n  - Add drm/xe patch to keep imported sg BOs off the LRU before attach\n    succeeds; the TTM fix alone is not sufficient for xe if the BO is\n    already LRU-visible. (Thomas)\n    v4 patch:\n    https://patchwork.freedesktop.org/patch/736663/?series=169129&rev=2\n  - Patch 1 (drm/ttm) carries Christian's Reviewed-by from v4.\n\nv6:\n  - Reworked the fix based on Thomas' suggestion. Instead of the TTM resv\n    individualization (v1-v5) plus the xe off-LRU/placement handling (v5),\n    just hold a dma-buf reference for the imported BO lifetime so the\n    shared resv can never be freed while the BO still references it.\n    Single xe patch, no TTM change. (Thomas)\n  - Take the reference in xe_bo_init_locked() before ttm_bo_init_reserved()\n    so a TTM creation failure is covered too (Thomas).\n  - Dropped the v5 series (drm/ttm + drm/xe off-LRU); the off-LRU approach\n    also regressed in CI BAT via ttm_bo_pipeline_gutting() creating a ghost\n    BO that outlived the exporter.\n    Link to v5: https://patchwork.freedesktop.org/series/169984/\n\nv7:\n  - Move changelog above --- so it stays in the commit message.\n  - Reorder changelog entries oldest-to-newest. (Thomas)\n\n(cherry picked from commit 3516f3fae6be35642f8f06f8a218da6425c0306a)\n\n## Affected\n\n- `Linux >= dd08ebf6c3525a7ea2186e636df064ea47281987 < c22d65d62b3318e237c0e5b1177d90ab83d9fe06`\n- `Linux >= dd08ebf6c3525a7ea2186e636df064ea47281987 < c1954c66662de477a8f4309335b775f7b07bd28b`\n- `Linux >= dd08ebf6c3525a7ea2186e636df064ea47281987 < ba8c4cbb31c6f81fa5b12d6e28f1f706040aff48`\n- `Linux >= dd08ebf6c3525a7ea2186e636df064ea47281987 < 62775525a27c3b0d56382e08ba81ee2d322058b6`\n- `Linux 6.8`\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"twilight","depthScore":43,"depthScoreParts":{"impact":42.9,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}