{"cve":"CVE-2026-64590","nvd":{"published":"2026-08-06T08:16:34.357","modified":"2026-08-23T13:16:32.443","status":"Received","description":"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   -> amdgpu_ttm_backend_bind\n    -> dma_buf_map_attachment\n     -> [udmabuf] map_udmabuf -> get_sg_table\n      -> dma_map_sgtable(dev, sg, direction, 0)  // attrs=0\n       -> debug_dma_map_sg -> add_dma_entry -> 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.","cvss_v4":null,"cvss_v3":null,"cwes":[],"references":["https://git.kernel.org/stable/c/01126abc11bcc6a45b664293b0b5df715be911d7","https://git.kernel.org/stable/c/0449a6583c0ee76778d314e4e82f166fc97fa9d8","https://git.kernel.org/stable/c/0db56e7eae932f8e2f3eb44ad1a63633d8f504f8","https://git.kernel.org/stable/c/34696563461c9a23177feb6d8aff43f4c0510278","https://git.kernel.org/stable/c/4a7c644e632741c2a3116a0d3da6c11de957a6ba"],"products":[],"source":"nvd","synced_at":"2026-10-19T22:47:10.050265369+00:00"},"epss":{"cve":"CVE-2026-64590","score":0.00165,"percentile":0.0566,"date":"2026-10-31"},"kev":null,"osv":[],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}