Linus Torvalds fixes Intel GPU driver bug with one-line patch

The bug represents a subtle but critical memory alignment issue in Intel's Xe GPU driver. The problem lay in how the driver managed memory stolen for CCS (Compute Core Scratch) — a performance feature used in modern Intel GPUs. By rounding up the memory address to a 128kB boundary without accounting for where that boundary fell, the driver inadvertently created a window where both the driver and the hardware engine could write to unallocated or already-allocated memory regions.

What made this bug particularly difficult to track was its non-deterministic impact. When the misaligned memory region overlapped with GPU page tables — the structures that map virtual memory to physical memory — the corruption was severe and immediate, manifesting as kernel timeouts. But in cases where the misaligned region contained less critical bitmap or texture data, the corruption went unnoticed until it manifested as intermittent screen glitches. This explains why Torvalds observed both predictable kernel job timeouts and occasional random screen corruption in the wild.

The two-year gap between the introduction of the bug and its becoming reliably reproducible suggests the issue was always latent, but user space behavior changes (such as different memory allocation patterns or GPU usage profiles) finally triggered consistent exposure of the flaw, allowing Torvalds to reproduce it reliably and fix it.