CVE-2026-74712: vdpa/mlx5: Fix buffer length in create_direct_keys()

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

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

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

vdpa/mlx5: Fix buffer length in create_direct_keys()

We have seen in our CI the following KASAN message:
BUG: KASAN: slab-out-of-bounds in cmd_exec+0x550/0xca0 [mlx5_core]
Read of size 272 at addr 0000000176795020 by task qemu-system-s39/82764
[...]
[<000011388ab3a7a0>] cmd_exec+0x550/0xca0 [mlx5_core]
[<000011388ab3b61c>] mlx5_cmd_exec_cb+0x25c/0x4f0 [mlx5_core]
[<000011388b21e82e>] mlx5_vdpa_exec_async_cmds+0x22e/0x5e0 [mlx5_vdpa]
[<000011388b21fd44>] create_direct_keys+0x954/0xef0 [mlx5_vdpa]
[...]
The buggy address is located 4128 bytes inside of
allocated 4384-byte region [0000000176794000, 0000000176795120)

So in essence we read 16 bytes beyond 4384-byte allocation.
create_direct_keys calculates the pointer and length for in and out
buffers.
The size calculation for in includes the entire structure
size (out + in + mtt[]) but the pointer passed to cmd_exec points only
to the 'in' field, skipping the 'out' field.

This causes mlx5_copy_to_msg() to read beyond the allocated buffer
by sizeof(out) bytes when copying command data.

Properly calculate the input size to match the pointer and allocation size.

The Linux kernel CVE team has assigned CVE-2026-74712 to this issue.


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

	Issue introduced in 6.12 with commit 0071b138d44af4296bf871e6624369ce697b4b15 and fixed in 6.12.104 with commit ec3bb289cf19d526224117d5d450a5fd9cbd5ab2
	Issue introduced in 6.12 with commit 0071b138d44af4296bf871e6624369ce697b4b15 and fixed in 6.18.45 with commit cde8931a25392670dd59a0acfcab87a830ab66c5
	Issue introduced in 6.12 with commit 0071b138d44af4296bf871e6624369ce697b4b15 and fixed in 7.1.9 with commit 6c8a9f7bc00301e533a5366384f3070a8e7f8430
	Issue introduced in 6.12 with commit 0071b138d44af4296bf871e6624369ce697b4b15 and fixed in 7.2 with commit 727e1f569855df83579edbd73dcb4a0723543a12

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-2026-74712
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/vdpa/mlx5/core/mr.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/ec3bb289cf19d526224117d5d450a5fd9cbd5ab2
	https://git.kernel.org/stable/c/cde8931a25392670dd59a0acfcab87a830ab66c5
	https://git.kernel.org/stable/c/6c8a9f7bc00301e533a5366384f3070a8e7f8430
	https://git.kernel.org/stable/c/727e1f569855df83579edbd73dcb4a0723543a12