Bug 2516464 (CVE-2026-72213)

Summary: CVE-2026-72213 kernel: mm/hugetlb: fix hugetlb cgroup rsvd charge/uncharge mismatch
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
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Priority: medium    
Version: unspecifiedCC: rhel-process-autobot, watson-tool-maintainers
Target Milestone: ---Keywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in the Linux kernel's huge page memory management (hugetlb). A mismatch in how reserved and non-reserved huge page control group (cgroup) charges are handled during memory allocation and deallocation can lead to an incorrect cgroup being uncharged. This issue results in a page counter underflow, which a local attacker could potentially leverage to cause a denial of service.
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Description OSIDB Bzimport 2026-08-15 06:13:53 UTC 
In the Linux kernel, the following vulnerability has been resolved:

mm/hugetlb: fix hugetlb cgroup rsvd charge/uncharge mismatch

In alloc_hugetlb_folio(), a single h_cg pointer is used for both the rsvd
and non-rsvd hugetlb cgroup charges.  When map_chg is set,
hugetlb_cgroup_charge_cgroup_rsvd() stores the charged cgroup in h_cg, but
the immediately following hugetlb_cgroup_charge_cgroup() overwrites h_cg
with the non-rsvd cgroup pointer.

As a result, hugetlb_cgroup_commit_charge_rsvd() stores the wrong
(non-rsvd) cgroup pointer into the folio's rsvd slot.

When the folio is later freed, free_huge_folio() unconditionally calls
both hugetlb_cgroup_uncharge_folio() and
hugetlb_cgroup_uncharge_folio_rsvd().  The rsvd uncharge reads back the
wrong cgroup from the folio and decrements a counter that was never
charged for that cgroup, causing a page_counter underflow:

  page_counter underflow: -512 nr_pages=512
  WARNING: mm/page_counter.c:61 at page_counter_cancel

Fix this by introducing a separate h_cg_rsvd pointer exclusively for the
rsvd charge path, keeping the rsvd and non-rsvd charges fully independent
through their charge, commit, and error uncharge paths.
Comment 1 Keith Grant 2026-08-18 15:46:06 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2026081546-CVE-2026-72213-712e@gregkh/T