dma-buf/udmabuf: skip redundant cpu sync to fix cacheline EEXIST warning

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-64590
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-08-06 08:16:34 UTC
Updated2026-08-06 08:16:34 UTC
DescriptionIn the Linux kernel, the following vulnerability has been resolved: dma-buf/udmabuf: skip redundant cpu sync to fix cacheline EEXIST warning When CONFIG_DMA_API_DEBUG_SG is enabled, importing a udmabuf into a DRM driver (e.g. amdgpu for video playback in GNOME Videos / Showtime) triggers a spurious warning: DMA-API: amdgpu 0000:03:00.0: cacheline tracking EEXIST, \ overlapping mappings aren't supported WARNING: kernel/dma/debug.c:619 at add_dma_entry+0x473/0x5f0 The call chain is: amdgpu_cs_ioctl -> amdgpu_ttm_backend_bind -> dma_buf_map_attachment -> [udmabuf] map_udmabuf -> get_sg_table -> dma_map_sgtable(dev, sg, direction, 0) // attrs=0 -> debug_dma_map_sg -> add_dma_entry -> EEXIST This happens because udmabuf builds a per-page scatter-gather list via sg_set_folio(). When begin_cpu_udmabuf() has already created an sg table mapped for the misc device, and an importer such as amdgpu maps the same pages for its own device via map_udmabuf(), the DMA debug infrastructure sees two active mappings whose physical addresses share cacheline boundaries and warns about the overlap. The DMA_ATTR_SKIP_CPU_SYNC flag suppresses this check in add_dma_entry() because it signals that no CPU cache maintenance is performed at map/unmap time, making the cacheline overlap harmless. All other major dma-buf exporters already pass this flag: - drm_gem_map_dma_buf() passes DMA_ATTR_SKIP_CPU_SYNC - amdgpu_dma_buf_map() passes DMA_ATTR_SKIP_CPU_SYNC The CPU sync at map/unmap time is also redundant for udmabuf: begin_cpu_udmabuf() and end_cpu_udmabuf() already perform explicit cache synchronization via dma_sync_sgtable_for_cpu/device() when CPU access is requested through the dma-buf interface. Pass DMA_ATTR_SKIP_CPU_SYNC to dma_map_sgtable() and dma_unmap_sgtable() in udmabuf to suppress the spurious warning and skip the redundant sync.

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected 284562e1f34874e267d4f499362c3816f8f6bc3f 0db56e7eae932f8e2f3eb44ad1a63633d8f504f8 git Not specified
CNA Linux Linux affected 284562e1f34874e267d4f499362c3816f8f6bc3f d6552f5cff795d60e629f37513ecf23d88fd2f82 git Not specified
CNA Linux Linux affected 284562e1f34874e267d4f499362c3816f8f6bc3f 34696563461c9a23177feb6d8aff43f4c0510278 git Not specified
CNA Linux Linux affected 284562e1f34874e267d4f499362c3816f8f6bc3f 0449a6583c0ee76778d314e4e82f166fc97fa9d8 git Not specified
CNA Linux Linux affected 284562e1f34874e267d4f499362c3816f8f6bc3f 504e2b4ab97a51d56d966cd36d0997ad30b65b2d git Not specified
CNA Linux Linux affected 5.6 Not specified
CNA Linux Linux unaffected 5.6 semver Not specified
CNA Linux Linux unaffected 6.6.148 6.6.* semver Not specified
CNA Linux Linux unaffected 6.12.96 6.12.* semver Not specified
CNA Linux Linux unaffected 6.18.39 6.18.* semver Not specified
CNA Linux Linux unaffected 7.1.4 7.1.* semver Not specified
CNA Linux Linux unaffected 7.2-rc1 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/34696563461c9a23177feb6d8aff43f4c0510278 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/d6552f5cff795d60e629f37513ecf23d88fd2f82 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/0449a6583c0ee76778d314e4e82f166fc97fa9d8 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/0db56e7eae932f8e2f3eb44ad1a63633d8f504f8 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/504e2b4ab97a51d56d966cd36d0997ad30b65b2d 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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