drm/xe: Add bounds check on pat_index to prevent OOB kernel read in madvise

Overview

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

drm/xe: Add bounds check on pat_index to prevent OOB kernel read in madvise

When user provides a bogus pat_index value through the madvise IOCTL, the xe_pat_index_get_coh_mode() function performs an array access without validating bounds. This allows a malicious user to trigger an out-of-bounds kernel read from the xe->pat.table array.

The vulnerability exists because the validation in madvise_args_are_sane() directly calls xe_pat_index_get_coh_mode(xe, args->pat_index.val) without first checking if pat_index is within [0, xe->pat.n_entries).

Although xe_pat_index_get_coh_mode() has a WARN_ON to catch this in debug builds, it still performs the unsafe array access in production kernels.

v2(Matthew Auld)

• Using array_index_nospec() to mitigate spectre attacks when the value is used

v3(Matthew Auld)

• Put the declarations at the start of the block

(cherry picked from commit 944a3329b05510d55c69c2ef455136e2fc02de29)

Affected

• Linux >= ada7486c5668db542a7d361268df931aca5b726a < ffba51100ff61792fefbae11ca38ac1987a818dd
• Linux >= ada7486c5668db542a7d361268df931aca5b726a < 79f52655567a6471ff3d0d6325ede91bb14461f4
• Linux >= ada7486c5668db542a7d361268df931aca5b726a < fbbe32618e97eff81577a01eb7d9adcd64a216d7
• Linux 6.18

Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.