---
cve: "CVE-2026-64590"
severity: "LOW"
cvss: 3.1
epss: "16%"
vendor: "Linux"
kev: false
exploited: false
published: "2026-08-06 08:16:34"
tags: [cve, security, low]
source: tsecurity.de CVE-Dossier
exported: "2026-09-12T03:10:07+02:00"
---

# CVE-2026-64590

> 3.1 LOW

## Beschreibung

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.

## Patch verfügbar (OSV)

- Kernel ≥ 5.10.266
- Kernel ≥ 5.15.217
- Kernel ≥ 6.1.184
- Kernel ≥ 6.6.148
- Kernel ≥ 6.12.96
- Kernel ≥ 6.18.39
- Kernel ≥ 7.1.4

## Referenzen

- <https://git.kernel.org/stable/c/0db56e7eae932f8e2f3eb44ad1a63633d8f504f8>
- <https://git.kernel.org/stable/c/d6552f5cff795d60e629f37513ecf23d88fd2f82>
- <https://git.kernel.org/stable/c/34696563461c9a23177feb6d8aff43f4c0510278>
- <https://git.kernel.org/stable/c/0449a6583c0ee76778d314e4e82f166fc97fa9d8>
- <https://git.kernel.org/stable/c/504e2b4ab97a51d56d966cd36d0997ad30b65b2d>
- <https://git.kernel.org/stable/c/01126abc11bcc6a45b664293b0b5df715be911d7>
- <https://git.kernel.org/stable/c/4a7c644e632741c2a3116a0d3da6c11de957a6ba>
- <https://git.kernel.org/stable/c/dd7f1e572f44d3d039dc77e3989f537196c3bf52>

---
_Exportiert aus dem [tsecurity.de CVE-Dossier](https://tsecurity.de/cve?cve=CVE-2026-64590) · Datenquellen: EUVD (ENISA), NVD, OSV, CISA KEV, FIRST EPSS, Exploit-DB, BSI BITS_