CVE-2026-98142

Status: UPDATED  |  Advisory ID: CVE-2026-98142

Key Details

Affected Products, Subsystems & Sectors

What to Know

In the Linux kernel, the following vulnerability has been resolved:

drm/cirrus-qemu: Validate BAR0 size during probe

The `cirrus-qemu` driver relies on `CIRRUS_VRAM_SIZE` (4 MB) to validate

framebuffer sizes. However, during PCI probe, the driver mapped BAR0

without verifying that its size matches `CIRRUS_VRAM_SIZE`.

If a PCI device with a BAR0 smaller than 4 MB is bound to the driver, the

mapped VRAM will be smaller than expected. Because validation checks assume

4 MB VRAM, framebuffers larger than the mapped memory can be created.

When the display plane is updated (e.g. during release),

`cirrus_primary_plane_helper_atomic_update()` copies the framebuffer to

VRAM using `drm_fb_memcpy()`. Writing past the end of the mapped I/O memory

causes a supervisor write page fault:

BUG: unable to handle page fault for address: ffffc9000389c000

...

RIP: 0010:memcpy_toio+0x7c/0xe0 arch/x86/lib/iomem.c:110

...

Call Trace:

<TASK>

iosys_map_memcpy_to include/linux/iosys-map.h:285 [inline]

drm_fb_memcpy+0x325/0x5d0 drivers/gpu/drm/drm_format_helper.c:442

cirrus_primary_plane_helper_atomic_update+0x98a/0xb00

drivers/gpu/drm/tiny/cirrus-qemu.c:358

drm_atomic_helper_commit_planes+0x626/0xea0

drivers/gpu/drm/drm_atomic_helper.c:3038

drm_atomic_helper_commit_tail+0x60/0x510

drivers/gpu/drm/drm_atomic_helper.c:1989

commit_tail+0x2b1/0x3c0 drivers/gpu/drm/drm_atomic_helper.c:2074

drm_atomic_helper_commit+0xa77/0xb10

drivers/gpu/drm/drm_atomic_helper.c:2312

Fix this by validating in `cirrus_pci_probe()` that the PCI BAR0 resource

is not less than `CIRRUS_VRAM_SIZE`, returning `-ENODEV` if it is less. (NVD)

What to Do

Monitor Linux's web page for any future patch releases.

References