{"id":"CVE-2026-64590","summary":"dma-buf/udmabuf: skip redundant cpu sync to fix cacheline EEXIST warning","details":"In the Linux kernel, the following vulnerability has been resolved:\n\ndma-buf/udmabuf: skip redundant cpu sync to fix cacheline EEXIST warning\n\nWhen CONFIG_DMA_API_DEBUG_SG is enabled, importing a udmabuf into a DRM\ndriver (e.g. amdgpu for video playback in GNOME Videos / Showtime)\ntriggers a spurious warning:\n\n  DMA-API: amdgpu 0000:03:00.0: cacheline tracking EEXIST, \\\n      overlapping mappings aren't supported\n  WARNING: kernel/dma/debug.c:619 at add_dma_entry+0x473/0x5f0\n\nThe call chain is:\n\n  amdgpu_cs_ioctl\n   -\u003e amdgpu_ttm_backend_bind\n    -\u003e dma_buf_map_attachment\n     -\u003e [udmabuf] map_udmabuf -\u003e get_sg_table\n      -\u003e dma_map_sgtable(dev, sg, direction, 0)  // attrs=0\n       -\u003e debug_dma_map_sg -\u003e add_dma_entry -\u003e EEXIST\n\nThis happens because udmabuf builds a per-page scatter-gather list via\nsg_set_folio().  When begin_cpu_udmabuf() has already created an sg\ntable mapped for the misc device, and an importer such as amdgpu maps\nthe same pages for its own device via map_udmabuf(), the DMA debug\ninfrastructure sees two active mappings whose physical addresses share\ncacheline boundaries and warns about the overlap.\n\nThe DMA_ATTR_SKIP_CPU_SYNC flag suppresses this check in\nadd_dma_entry() because it signals that no CPU cache maintenance is\nperformed at map/unmap time, making the cacheline overlap harmless.\n\nAll other major dma-buf exporters already pass this flag:\n  - drm_gem_map_dma_buf() passes DMA_ATTR_SKIP_CPU_SYNC\n  - amdgpu_dma_buf_map() passes DMA_ATTR_SKIP_CPU_SYNC\n\nThe CPU sync at map/unmap time is also redundant for udmabuf:\nbegin_cpu_udmabuf() and end_cpu_udmabuf() already perform explicit\ncache synchronization via dma_sync_sgtable_for_cpu/device() when CPU\naccess is requested through the dma-buf interface.\n\nPass DMA_ATTR_SKIP_CPU_SYNC to dma_map_sgtable() and\ndma_unmap_sgtable() in udmabuf to suppress the spurious warning and\nskip the redundant sync.","modified":"2026-08-08T03:32:18.609679591Z","published":"2026-08-06T07:13:47.888Z","database_specific":{"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/64xxx/CVE-2026-64590.json","cna_assigner":"Linux"},"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/0449a6583c0ee76778d314e4e82f166fc97fa9d8"},{"type":"WEB","url":"https://git.kernel.org/stable/c/0db56e7eae932f8e2f3eb44ad1a63633d8f504f8"},{"type":"WEB","url":"https://git.kernel.org/stable/c/34696563461c9a23177feb6d8aff43f4c0510278"},{"type":"WEB","url":"https://git.kernel.org/stable/c/504e2b4ab97a51d56d966cd36d0997ad30b65b2d"},{"type":"WEB","url":"https://git.kernel.org/stable/c/d6552f5cff795d60e629f37513ecf23d88fd2f82"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/64xxx/CVE-2026-64590.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-64590"},{"type":"PACKAGE","url":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"284562e1f34874e267d4f499362c3816f8f6bc3f"},{"fixed":"0db56e7eae932f8e2f3eb44ad1a63633d8f504f8"},{"fixed":"d6552f5cff795d60e629f37513ecf23d88fd2f82"},{"fixed":"34696563461c9a23177feb6d8aff43f4c0510278"},{"fixed":"0449a6583c0ee76778d314e4e82f166fc97fa9d8"},{"fixed":"504e2b4ab97a51d56d966cd36d0997ad30b65b2d"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-64590.json"}},{"package":{"name":"Kernel","ecosystem":"Linux"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"5.6.0"},{"fixed":"6.6.148"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.7.0"},{"fixed":"6.12.96"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.13.0"},{"fixed":"6.18.39"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.19.0"},{"fixed":"7.1.4"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-64590.json"}}],"schema_version":"1.8.0"}