CVE-2026-64590

What the bug is

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.

Where it lives

The fix touches these files. If the subsystem is one you do not use, the practical exposure is lower, though the package is still the vulnerable one.

drivers/dma-buf/udmabuf.c

What this is

USERSPACE DMA BUFFER DRIVERMAINTAINERS section matched on drivers/dma-buf/udmabuf.c · dri-devel@lists.freedesktop.org · Maintained

Check it on the machine

grep -wE 'CONFIG_DMA_SHARED_BUFFER|CONFIG_UDMABUF' /boot/config-$(uname -r)

Reads the booted kernel's own configuration, on the machine and nowhere else. =y is built in, =m is a module, and an is not set line means the code is not there.

Show whether Debian builds this, per release

Debian does not build this code in 1 release. It does build it in 4 releases, so the answer depends on which release the machine runs.

• bookwormn
• trixieYnot built on armel/rpi, armhf/armmp, armhf/armmp-lpae, armhf/rt/armmp, ppc64el/powerpc64le, ppc64el/powerpc64le-64k, riscv64/riscv64, s390x/s390x
• forky, sidYnot built on armhf/armmp, armhf/armmp-lpae, loong64/loong64, ppc64el/powerpc64le, ppc64el/powerpc64le-64k, riscv64/riscv64, s390x/s390x
• bookworm · linux-6.12Ynot built on armhf/armmp, armhf/armmp-lpae, armhf/rt/armmp, ppc64el/powerpc64le, ppc64el/powerpc64le-64k

n

not enabled on any flavour - this release does not build the code

Y

built in where it is built at all; some flavours do not build it

Build switches

CONFIG_DMA_SHARED_BUFFER, CONFIG_UDMABUF

Reads as

all on means the file is compiled; any one off means it is not.

From the configuration Debian publishes for every kernel flavour it builds. It covers only the architectures Debian ships a linux-config package for, and nothing about a kernel you built yourself. Debian's own status above stays authoritative about the source package.MAINTAINERS kbuild Makefiles Debian linux-config packages

Signals

Published

2026-08-06 (2 months ago)source

CVSS

no vector published, unrated

Attack vector

not published

EPSS

0.17%, higher than 5.3% of all CVEssource

CISA KEV

not listedthe KEV catalogue

Debian urgency

not yet assignedsource

Subsystem

drivers/dma-buf

Upstream fixes

The versions the CNA records as introducing and fixing this, and the commit for each. source

Introduced	Fixed in	Commit
5.6	5.10.266	4a7c644e6327
5.6	5.15.217	01126abc11bc
5.6	6.1.184	dd7f1e572f44
5.6	6.6.148	0db56e7eae93
5.6	6.12.96	d6552f5cff79
5.6	6.18.39	34696563461c
5.6	7.1.4	0449a6583c0e
5.6	7.2	504e2b4ab97a

Debian advisories