Bug 2517058 (CVE-2026-74514)

Summary: CVE-2026-74514 kernel: KVM: s390: pci: Fix memory accounting for pinned/unpinned pages
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
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Version: unspecifiedCC: rhel-process-autobot, watson-tool-maintainers
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Hardware: All   
OS: Linux   
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A flaw was found in the KVM (Kernel-based Virtual Machine) s390 PCI component. Incorrect memory accounting in the `account_mem()` and `unaccount_mem()` functions, specifically related to the handling of pinned and unpinned pages, can lead to a resource leak. This occurs because the reference count for user structures is not properly decremented, and memory accounting might be performed in a different process context than the one that originally pinned the pages. This issue could potentially lead to resource exhaustion, resulting in a Denial of Service (DoS) for the system.
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Description OSIDB Bzimport 2026-08-15 12:47:23 UTC 
In the Linux kernel, the following vulnerability has been resolved:

KVM: s390: pci: Fix memory accounting for pinned/unpinned pages

The account_mem() and unaccount_mem() functions call get_uid() which
increments the reference count of struct user_struct on every invocation.
But we don't decrement the count by calling free_uid(). It also
accounted/unaccounted the pages against the current->mm. But its possible
the unaccount_mem() can be called from a different process context than the
one that originally pinned the pages.

Let's fix this by storing the pinning process user_struct and mm_struct
when accounting for pinned pages, and subsequently free these resources
when the pages are unpinned.

[borntraeger.com: Fixed whitespace]
Comment 1 Mauro Matteo Cascella 2026-08-19 17:01:56 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2026081543-CVE-2026-74514-9f7b@gregkh/T