Bug 2492760 (CVE-2026-53187)

Summary: CVE-2026-53187 kernel: RDMA/core: Validate cpu_id against nr_cpu_ids in DMAH alloc
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security <prodsec-ir-bot>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: 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 RDMA/core component. A local attacker could supply an invalid `cpu_id` through the `UVERBS_ATTR_ALLOC_DMAH_CPU_ID` attribute without proper validation. This improper validation could lead to an out-of-bounds read of the `cpumask` bitmap. On systems configured with `CONFIG_DEBUG_PER_CPU_MAPS` and `panic_on_warn`, this vulnerability could result in a system reboot, leading to a denial of service.
 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 2026-06-25 10:04:18 UTC 
In the Linux kernel, the following vulnerability has been resolved:

RDMA/core: Validate cpu_id against nr_cpu_ids in DMAH alloc

The cpu_id attribute supplied by user space through
UVERBS_ATTR_ALLOC_DMAH_CPU_ID is passed directly to cpumask_test_cpu()
without first verifying that the value is within the valid CPU range.

Passing such untrusted data to cpumask_test_cpu() may lead to an
out-of-bounds read of the underlying cpumask bitmap: the helper expands
to a test_bit() that indexes the bitmap by cpu_id / BITS_PER_LONG with
no bound check.

In addition, on kernels built with CONFIG_DEBUG_PER_CPU_MAPS it trips
the WARN_ON_ONCE() in cpumask_check(); combined with panic_on_warn this
turns a bad user input into a machine reboot.

Reject any cpu_id that is not smaller than nr_cpu_ids with -EINVAL
before it is used.

Reported by Smatch.
Comment 1 Keith Grant 2026-06-25 23:32:12 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2026062556-CVE-2026-53187-786d@gregkh/T