FKIE_CVE-2026-64590

Vulnerability from fkie_nvd - Published: 2026-08-06 08:16 - Updated: 2026-08-06 08:16
Severity
Summary
In 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.
References
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/0449a6583c0ee76778d314e4e82f166fc97fa9d8
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/0db56e7eae932f8e2f3eb44ad1a63633d8f504f8
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/34696563461c9a23177feb6d8aff43f4c0510278
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/504e2b4ab97a51d56d966cd36d0997ad30b65b2d
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/d6552f5cff795d60e629f37513ecf23d88fd2f82
Impacted products
Vendor Product Version
To clipboard 

{
  "affected": [
    {
      "affectedData": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "drivers/dma-buf/udmabuf.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "0db56e7eae932f8e2f3eb44ad1a63633d8f504f8",
              "status": "affected",
              "version": "284562e1f34874e267d4f499362c3816f8f6bc3f",
              "versionType": "git"
            },
            {
              "lessThan": "d6552f5cff795d60e629f37513ecf23d88fd2f82",
              "status": "affected",
              "version": "284562e1f34874e267d4f499362c3816f8f6bc3f",
              "versionType": "git"
            },
            {
              "lessThan": "34696563461c9a23177feb6d8aff43f4c0510278",
              "status": "affected",
              "version": "284562e1f34874e267d4f499362c3816f8f6bc3f",
              "versionType": "git"
            },
            {
              "lessThan": "0449a6583c0ee76778d314e4e82f166fc97fa9d8",
              "status": "affected",
              "version": "284562e1f34874e267d4f499362c3816f8f6bc3f",
              "versionType": "git"
            },
            {
              "lessThan": "504e2b4ab97a51d56d966cd36d0997ad30b65b2d",
              "status": "affected",
              "version": "284562e1f34874e267d4f499362c3816f8f6bc3f",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "drivers/dma-buf/udmabuf.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "5.6"
            },
            {
              "lessThan": "5.6",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.6.*",
              "status": "unaffected",
              "version": "6.6.148",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.96",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.39",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.1.*",
              "status": "unaffected",
              "version": "7.1.4",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.2-rc1",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "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\u0027t 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."
    }
  ],
  "id": "CVE-2026-64590",
  "lastModified": "2026-08-06T08:16:34.357",
  "metrics": {},
  "published": "2026-08-06T08:16:34.357",
  "references": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/0449a6583c0ee76778d314e4e82f166fc97fa9d8"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/0db56e7eae932f8e2f3eb44ad1a63633d8f504f8"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/34696563461c9a23177feb6d8aff43f4c0510278"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/504e2b4ab97a51d56d966cd36d0997ad30b65b2d"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/d6552f5cff795d60e629f37513ecf23d88fd2f82"
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Received"
}



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