Bug 2400594 (CVE-2025-39902)

Summary: CVE-2025-39902 kernel: mm/slub: avoid accessing metadata when pointer is invalid in object_err()
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
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   
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A flaw was found in the Linux kernel’s SLUB memory allocator (mm/slub). The function object_err() — used for debugging object metadata (freelist pointer, redzone, etc.) — can access invalid pointers when reporting corruption, leading to a crash. In some cases, due to freelist corruption (e.g., detected by alloc_consistency_checks()), the pointer passed to object_err() is invalid; instead of accessing metadata.
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
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Description OSIDB Bzimport 2025-10-01 08:01:24 UTC 
In the Linux kernel, the following vulnerability has been resolved:

mm/slub: avoid accessing metadata when pointer is invalid in object_err()

object_err() reports details of an object for further debugging, such as
the freelist pointer, redzone, etc. However, if the pointer is invalid,
attempting to access object metadata can lead to a crash since it does
not point to a valid object.

One known path to the crash is when alloc_consistency_checks()
determines the pointer to the allocated object is invalid because of a
freelist corruption, and calls object_err() to report it. The debug code
should report and handle the corruption gracefully and not crash in the
process.

In case the pointer is NULL or check_valid_pointer() returns false for
the pointer, only print the pointer value and skip accessing metadata.
Comment 1 Alexander B 2025-10-02 10:28:32 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2025100118-CVE-2025-39902-0fe1@gregkh/T