CVE-2026-72213

Summary

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.

Affected Software

Weaknesses

References

• https://git.kernel.org/stable/c/5c32ae4a91fb5f4941328e0c1720a7fa4189c3bd
• https://git.kernel.org/stable/c/1697d253f51cf5e3825a3423ff49e128a3502ab2
• https://git.kernel.org/stable/c/b785f2bd9496facedc0a031be09cddcd1d3c84d3
• https://git.kernel.org/stable/c/15807d0ddde37407af72859426b654f3d1972b00

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