Bug 2513329 (CVE-2026-68274)

Summary: CVE-2026-68274 kernel: drm/xe/guc: Fix buffer overflow in steered register list allocation
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security <prodsec-ir-bot>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: akhatavk, aos-team-art-private, asdas, dpaolell, jdelft, jupierce, lgarciaa, mbiarnes, ppalepu, ppostler, prdhamdh, rhel-process-autobot, sghai, sidsharm, suppawar, vlaad, watson-tool-maintainers
Target Milestone: ---Keywords: Security
Target Release: ---   
Hardware: All   
OS: Linux   
Whiteboard:
Fixed In Version: Doc Type: ---
Doc Text:
A flaw was found in the Linux kernel's `drm/xe/guc` component. An incorrect calculation of the steered register list allocation size can lead to a buffer overflow. This allows an attacker to write past the allocated buffer, corrupting adjacent memory objects. This memory corruption can result in system instability and a denial of service.
 Story Points: ---
Clone Of: Environment:
Last Closed: Type: ---
Regression: --- Mount Type: ---
Documentation: --- CRM:
Verified Versions: Category: ---
oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
Embargoed:

Description OSIDB Bzimport 2026-08-10 12:31:18 UTC 
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)