UBUNTU-CVE-2026-64590: Medium severity ubuntu/linux-hwe-edge vulnerability
In the Linux kernel, the following vulnerability has been resolved: dma-buf/udmabuf: skip redundant cpu sync to fix cacheline EEXIST warning When CONFIGDMAAPIDEBUGSG 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 adddmaentry+0x473/0x5f0 The call chain is: amdgpucsioctl -> amdgputtmbackendbind -> dmabufmapattachment -> [udmabuf] mapudmabuf -> getsgtable -> dmamapsgtable(dev, sg, direction, 0) // attrs=0 -> debugdmamapsg -> adddmaentry -> EEXIST This happens because udmabuf builds a per-page scatter-gather list via sgsetfolio(). When begincpuudmabuf() 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 mapudmabuf(), the DMA debug infrastructure sees two active mappings whose physical addresses share cacheline boundaries and warns about the overlap. The DMAATTRSKIPCPUSYNC flag suppresses this check in adddmaentry() 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: - drmgemmapdmabuf() passes DMAATTRSKIPCPUSYNC - amdgpudmabufmap() passes DMAATTRSKIPCPUSYNC The CPU sync at map/unmap time is also redundant for udmabuf: begincpuudmabuf() and endcpuudmabuf() already perform explicit cache synchronization via dmasyncsgtableforcpu/device() when CPU access is requested through the dma-buf interface. Pass DMAATTRSKIPCPUSYNC to dmamapsgtable() and dmaunmapsgtable() in udmabuf to suppress the spurious warning and skip the redundant sync.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
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ubuntu/linuxto a version that resolves this vulnerability.Fixed in 6.8.0-147.147 - Upgrade
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ubuntu/linux-awsto a version that resolves this vulnerability.Fixed in 6.8.0-1067.70 - Upgrade
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ubuntu/linux-aws-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-1012.12~24.04.1 - Upgrade
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ubuntu/linux-azureto a version that resolves this vulnerability.Fixed in 6.8.0-1071.79 - Upgrade
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ubuntu/linux-azure-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-1014.14~24.04.1 - Upgrade
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ubuntu/linux-gcpto a version that resolves this vulnerability.Fixed in 6.8.0-1071.79 - Upgrade
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ubuntu/linux-gcp-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-1011.11~24.04.1 - Upgrade
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ubuntu/linux-gkeopto a version that resolves this vulnerability.Fixed in 6.8.0-1052.56 - Upgrade
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ubuntu/linux-hwe-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-31.31~24.04.1 - Upgrade
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ubuntu/linux-ibmto a version that resolves this vulnerability.Fixed in 6.8.0-1067.68 - Upgrade
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ubuntu/linux-lowlatencyto a version that resolves this vulnerability.Fixed in 6.8.0-147.147.1 - Upgrade
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ubuntu/linux-nvidia-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-1018.18~24.04.1 - Upgrade
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ubuntu/linux-oracleto a version that resolves this vulnerability.Fixed in 6.8.0-1064.67 - Upgrade
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ubuntu/linux-bluefieldto a version that resolves this vulnerability.Fixed in 6.8.0-1033.38 - Upgrade
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ubuntu/linux-realtimeto a version that resolves this vulnerability.Fixed in 6.8.1-1062.63 - Upgrade
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ubuntu/linuxto a version that resolves this vulnerability.Fixed in 7.0.0-31.31 - Upgrade
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ubuntu/linux-awsto a version that resolves this vulnerability.Fixed in 7.0.0-1012.12 - Upgrade
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ubuntu/linux-azureto a version that resolves this vulnerability.Fixed in 7.0.0-1014.14 - Upgrade
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ubuntu/linux-gcpto a version that resolves this vulnerability.Fixed in 7.0.0-1011.11 - Upgrade
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ubuntu/linux-gketo a version that resolves this vulnerability.Fixed in 7.0.0-1006.7 - Upgrade
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ubuntu/linux-nvidia-bosto a version that resolves this vulnerability.Fixed in 7.0.0-2018.18 - Upgrade
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ubuntu/linux-oem-7.0to a version that resolves this vulnerability.Fixed in 7.0.0-1013.13 - Upgrade
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ubuntu/linux-raspito a version that resolves this vulnerability.Fixed in 7.0.0-1019.19 - Upgrade
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ubuntu/linux-realtimeto a version that resolves this vulnerability.Fixed in 7.0.0-31.31.1 - Upgrade
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ubuntu/linux-riscvto a version that resolves this vulnerability.Fixed in 7.0.0-31.31.1 - Compensating control
In udmabuf, pass DMA_ATTR_SKIP_CPU_SYNC to dma_map_sgtable() and dma_unmap_sgtable() to suppress the spurious DMA-API cacheline EEXIST warning and avoid redundant CPU synchronization.
Event History
Frequently Asked Questions
Which systems are likely to encounter the warning?
Systems with CONFIG_DMA_API_DEBUG_SG enabled can encounter it when a udmabuf is imported into a DRM driver. The described example is amdgpu during video playback in GNOME Videos or Showtime.
How can I tell whether this issue is occurring?
The DMA debugging output reports a cacheline tracking EEXIST condition and states that overlapping mappings are not supported. The described call path includes amdgpu_cs_ioctl, dma_buf_map_attachment, map_udmabuf, dma_map_sgtable, and add_dma_entry.