CVE-2026-98142
UnknownSummary
In the Linux kernel, the drm/cirrus-qemu driver did not validate the BAR0 size during PCI probe. If a PCI device with BAR0 smaller than 4 MB (CIRRUS_VRAM_SIZE) was bound to the driver, the mapped VRAM was smaller than expected, allowing framebuffers larger than the mapped memory to be created and copied out of bounds, causing a supervisor write page fault.
Risk Assessment
This can lead to a kernel crash (panic) and denial of service on systems where a PCI device with BAR0 smaller than 4 MB is present or emulated. In virtualized environments or with unprivileged PCI device access, it may be exploited to destabilize the system.
Recommendation
Update the Linux kernel to a version containing the fix that validates BAR0 size in cirrus_pci_probe() (returning -ENODEV for BAR0 < CIRRUS_VRAM_SIZE). Until patched, avoid binding the cirrus-qemu driver to PCI devices with BAR0 smaller than 4 MB.
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Original NVD description (English source)
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.
Vulnerability data from NVD (NIST) · CISA KEV · EPSS