Bug 2521368 (CVE-2026-74712)

Summary:	CVE-2026-74712 kernel: vdpa/mlx5: Fix buffer length in create_direct_keys()
Product:	[Other] Security Response	Reporter:	OSIDB Bzimport <bzimport>
Component:	vulnerability	Assignee:	Product Security DevOps Team <prodsec-dev>
Status:	NEW ---	QA Contact:
Severity:	medium	Docs Contact:
Priority:	medium
Version:	unspecified	CC:	rhel-process-autobot, 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 `vdpa/mlx5` driver. This vulnerability occurs due to an incorrect calculation of buffer length within the `create_direct_keys()` function, causing the system to read beyond its allocated memory boundaries. A local attacker could exploit this memory corruption to trigger a system crash, leading to a denial of service (DoS), or potentially gain access to sensitive information.	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 2026-08-22 15:42:05 UTC

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.

Comment 1 gkamathe 2026-08-24 08:03:30 UTC

Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2026082238-CVE-2026-74712-1399@gregkh/T