CVE-2026-68305: drm/xe/vf: Add drm_dev guards when detaching CCS read/write buffers

From: Greg Kroah-Hartman <[email protected]>

Description
===========

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

drm/xe/vf: Add drm_dev guards when detaching CCS read/write buffers

CCS read/write buffers are freed during BO destruction. In some cases,
BOs may be destroyed after the device is unbound but while the DRM
structure remains valid, leading to NULL pointer dereferences when
accessing device resources.

BUG: kernel NULL pointer dereference, address: 0000000000000000
PGD 0 P4D 0
Oops: Oops: 0000 [#1] SMP NOPTI
CPU: 0 UID: 0 PID: 9376 Comm: xe_pat Not tainted 7.2.0-rc2+ #1 PREEMPT(lazy)
RIP: 0010:xe_sriov_vf_ccs_rw_update_bb_addr+0x4d/0xa0 [xe]
RSP: 0018:ffffcf304110b9c8 EFLAGS: 00010246
RAX: ffff8a85c38a0a00 RBX: 00000000810ef000 RCX: 0000000000000000
RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffff8a85c39c1888
RBP: ffffcf304110b9e8 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: ffff8a85c39c1888
R13: 0000000000000000 R14: ffff8a85c39b4f28 R15: ffff8a85c3885000
FS:  0000000000000000(0000) GS:ffff8a878b809000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000000 CR3: 000000010314a002 CR4: 0000000000772ef0
PKRU: 55555554
Call Trace:
 <TASK>
 xe_migrate_ccs_rw_copy_clear+0x98/0x120 [xe]
 xe_sriov_vf_ccs_detach_bo+0x2c/0x60 [xe]
 xe_ttm_bo_delete_mem_notify+0xc8/0xe0 [xe]
 ttm_bo_cleanup_memtype_use+0x26/0x80 [ttm]
 ttm_bo_release+0x29e/0x2d0 [ttm]
 ttm_bo_fini+0x39/0x70 [ttm]
 xe_gem_object_free+0x1f/0x30 [xe]
 drm_gem_object_free+0x1d/0x40
 ttm_bo_vm_close+0x5f/0x90 [ttm]
 remove_vma+0x2c/0x70
 tear_down_vmas+0x63/0xf0
 exit_mmap+0x20d/0x3f0
 __mmput+0x45/0x170
 mmput+0x31/0x40
 do_exit+0x2ba/0xac0
 do_group_exit+0x2d/0xb0
 __x64_sys_exit_group+0x18/0x20
 x64_sys_call+0x14a0/0x2390
 do_syscall_64+0xdd/0x640
 ? count_memcg_events+0xea/0x240
 ? handle_mm_fault+0x1ec/0x2f0

(cherry picked from commit 1ae415a6eefe5004954a1d352b1718faca8844ef)

The Linux kernel CVE team has assigned CVE-2026-68305 to this issue.


Affected and fixed versions
===========================

	Issue introduced in 6.18 with commit 864690cf4dd62482b6dd049d82c509886c904303 and fixed in 7.1.6 with commit 523ed2831ee55b2a1edabdea96781651f9df9685
	Issue introduced in 6.18 with commit 864690cf4dd62482b6dd049d82c509886c904303 and fixed in 7.2-rc5 with commit 4c92afb4c143526d340545ca581e88e6952ea511

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2026-68305
will be updated if fixes are backported, please check that for the most
up to date information about this issue.


Affected files
==============

The file(s) affected by this issue are:
	drivers/gpu/drm/xe/xe_migrate.c
	drivers/gpu/drm/xe/xe_migrate.h
	drivers/gpu/drm/xe/xe_sriov_vf_ccs.c


Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/523ed2831ee55b2a1edabdea96781651f9df9685
	https://git.kernel.org/stable/c/4c92afb4c143526d340545ca581e88e6952ea511