CVE-2026-46220

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

drm/amdgpu/sdma4: replace BUG_ON with WARN_ON in fence emission

sdma_v4_0_ring_emit_fence() contains two BUG_ON(addr & 0x3) assertions that verify fence writeback addresses are dword-aligned. These assertions can be reached from unprivileged userspace via crafted DRM_IOCTL_AMDGPU_CS submissions, causing a fatal kernel panic in a scheduler worker thread.

Replace both BUG_ON() calls with WARN_ON() to log the condition without crashing the kernel. A misaligned fence address at this point indicates a driver bug, but crashing the kernel is never the correct response when the assertion is reachable from userspace.

The CS IOCTL path is the correct place to filter invalid submissions; the ring emission callback is too late to do anything about it.

(cherry picked from commit b90250bd933afd1ba94d86d6b13821997b22b18e)

Weakness

The product contains an assert() or similar statement that can be triggered by an attacker, which leads to an application exit or other behavior that is more severe than necessary.

Affected Software

Extended Description

While assertion is good for catching logic errors and reducing the chances of reaching more serious vulnerability conditions, it can still lead to a denial of service. For example, if a server handles multiple simultaneous connections, and an assert() occurs in one single connection that causes all other connections to be dropped, this is a reachable assertion that leads to a denial of service.

Potential Mitigations

References

• https://git.kernel.org/stable/c/0b91ea46bb68abf98a082bf239092253bbd6aaa2
• https://git.kernel.org/stable/c/25e7d56a39657d56d1ea6d78992f7ed15dedb412
• https://git.kernel.org/stable/c/4f7ca00fa91daf0795ec6b3b130c5ebba1f155fe
• https://git.kernel.org/stable/c/78d2e624fa073c14970aa097adcf3ea31c157a66
• https://git.kernel.org/stable/c/a4fd82fb0757c180bf622907397c528b89a827b2
• https://git.kernel.org/stable/c/d331fb241a4602253976ddd65144a8ba2b05665d
• https://git.kernel.org/stable/c/d4c56932d29773e278be6a65a5384a36c95b89a4
• https://git.kernel.org/stable/c/ecaa80318e900ca0c3f687742ede33b41cfd2f8e