CVE-2026-68260: drm/imagination: acquire vm_ctx->lock before mapping memory to GPU VM

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

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

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

drm/imagination: acquire vm_ctx->lock before mapping memory to GPU VM

The drm gpuvm code doesn't protect find operation against map operation,
and the driver needs to ensure a map operation shouldn't happen when a
find operation is in progress.

In some cases a find operation will be in progress when doing map/unmap
operations, and the find operation will do a NULL pointer dereference.

An example of the stack trace of such NULL dereference is shown below:

```
Unable to handle kernel access to user memory without uaccess routines at
virtual address 0000000000000010

[<ffffffff01e989d4>] drm_gpuva_find+0x28/0x6c [drm_gpuvm]
[<ffffffff01ed3a40>] pvr_vm_unmap+0x34/0x68 [powervr]
[<ffffffff01ec69da>] pvr_ioctl_vm_unmap+0x2e/0x50 [powervr]
[<ffffffff8080ce0a>] drm_ioctl_kernel+0x8e/0xdc
[<ffffffff8080d016>] drm_ioctl+0x1be/0x3e0
[<ffffffff802bec3e>] __riscv_sys_ioctl+0xba/0xc4
[<ffffffff80d858b2>] do_trap_ecall_u+0x23e/0x3f4
[<ffffffff80d92288>] handle_exception+0x168/0x174
```

As all occurences of drm_gpuva_find*() are already guarded by
vm_ctx->lock, make pvr_vm_map() to acquire this lock to prevent
disturbing any find operation. This fixes the NULL deference problem in
drm_gpuva_find*().

The Linux kernel CVE team has assigned CVE-2026-68260 to this issue.


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

	Issue introduced in 6.8 with commit ff5f643de0bf27874c4033cd57a0bd034b5c7d11 and fixed in 6.12.101 with commit 1f1f2618e44b21a7d4eb30d3bbd7e015ffbbbadf
	Issue introduced in 6.8 with commit ff5f643de0bf27874c4033cd57a0bd034b5c7d11 and fixed in 6.18.42 with commit 6253bb56bb2ebdf317d8b599ce737a2510cc2e17
	Issue introduced in 6.8 with commit ff5f643de0bf27874c4033cd57a0bd034b5c7d11 and fixed in 7.1.6 with commit 15f58d44c24477a6ebffa44ec05207b81cfa55d9
	Issue introduced in 6.8 with commit ff5f643de0bf27874c4033cd57a0bd034b5c7d11 and fixed in 7.2-rc5 with commit 17e2030f37600994440f875dc410615d5c66ee6d

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-2026-68260
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/imagination/pvr_vm.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/1f1f2618e44b21a7d4eb30d3bbd7e015ffbbbadf
	https://git.kernel.org/stable/c/6253bb56bb2ebdf317d8b599ce737a2510cc2e17
	https://git.kernel.org/stable/c/15f58d44c24477a6ebffa44ec05207b81cfa55d9
	https://git.kernel.org/stable/c/17e2030f37600994440f875dc410615d5c66ee6d