CVE-2026-68274

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

drm/xe/guc: Fix buffer overflow in steered register list allocation

The size calculation for the steered register extarray uses only the geometry DSS mask (g_dss_mask) to determine the number of entries to allocate:

total = bitmap_weight(gt->fuse_topo.g_dss_mask, …) * steer_reg_num;

However, the filling loop uses for_each_dss_steering(), which iterates over for_each_dss(), defined as the union of g_dss_mask and c_dss_mask (geometry + compute DSS). On platforms with compute-only DSS bits, the loop writes past the allocated buffer, corrupting adjacent slab objects.

This manifests as list_del corruption and SLUB redzone overwrites during drm_managed_release on device unbind, since the overflow corrupts the drmres list_head of neighboring allocations.

Fix by computing the allocation size using the union of both DSS masks, matching the iteration pattern of for_each_dss_steering().

– v2:

• use bitmap_weighted_or() (Zhanjun)

(cherry picked from commit 0a78a44f4901aa6c9263e66be7fce02282f1109f)

Weakness

The product writes data past the end, or before the beginning, of the intended buffer.

Affected Software

Potential Mitigations

• Use a language that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.

• For example, many languages that perform their own memory management, such as Java and Perl, are not subject to buffer overflows. Other languages, such as Ada and C#, typically provide overflow protection, but the protection can be disabled by the programmer.

• Be wary that a language’s interface to native code may still be subject to overflows, even if the language itself is theoretically safe.

• Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.

• Examples include the Safe C String Library (SafeStr) by Messier and Viega [REF-57], and the Strsafe.h library from Microsoft [REF-56]. These libraries provide safer versions of overflow-prone string-handling functions.

• Use automatic buffer overflow detection mechanisms that are offered by certain compilers or compiler extensions. Examples include: the Microsoft Visual Studio /GS flag, Fedora/Red Hat FORTIFY_SOURCE GCC flag, StackGuard, and ProPolice, which provide various mechanisms including canary-based detection and range/index checking.

• D3-SFCV (Stack Frame Canary Validation) from D3FEND [REF-1334] discusses canary-based detection in detail.

• Consider adhering to the following rules when allocating and managing an application’s memory:

• Run or compile the software using features or extensions that randomly arrange the positions of a program’s executable and libraries in memory. Because this makes the addresses unpredictable, it can prevent an attacker from reliably jumping to exploitable code.

• Examples include Address Space Layout Randomization (ASLR) [REF-58] [REF-60] and Position-Independent Executables (PIE) [REF-64]. Imported modules may be similarly realigned if their default memory addresses conflict with other modules, in a process known as “rebasing” (for Windows) and “prelinking” (for Linux) [REF-1332] using randomly generated addresses. ASLR for libraries cannot be used in conjunction with prelink since it would require relocating the libraries at run-time, defeating the whole purpose of prelinking.

• For more information on these techniques see D3-SAOR (Segment Address Offset Randomization) from D3FEND [REF-1335].

• Use a CPU and operating system that offers Data Execution Protection (using hardware NX or XD bits) or the equivalent techniques that simulate this feature in software, such as PaX [REF-60] [REF-61]. These techniques ensure that any instruction executed is exclusively at a memory address that is part of the code segment.

• For more information on these techniques see D3-PSEP (Process Segment Execution Prevention) from D3FEND [REF-1336].

References

• https://git.kernel.org/stable/c/632ecc90e1ca5d3b6822bb4d08f84a175b6c42c0
• https://git.kernel.org/stable/c/a9a020f3c11eba6573b699f9cf9245a51b025ade
• https://git.kernel.org/stable/c/b485bfb45555163bfa5f565d6a3415fcb3035b02