UBUNTU-CVE-2025-37958
In the Linux kernel, the following vulnerability has been resolved: mm/huge_memory: fix dereferencing invalid pmd migration entry When migrating a THP, concurrent access to the PMD migration entry during a deferred split scan can lead to an invalid address access, as illustrated below. To prevent this invalid access, it is necessary to check the PMD migration entry and return early. In this context, there is no need to use pmd_to_swp_entry and pfn_swap_entry_to_page to verify the equality of the target folio. Since the PMD migration entry is locked, it cannot be served as the target. Mailing list discussion and explanation from Hugh Dickins: "An anon_vma lookup points to a location which may contain the folio of interest, but might instead contain another folio: and weeding out those other folios is precisely what the "folio != pmd_folio((*pmd)" check (and the "risk of replacing the wrong folio" comment a few lines above it) is for." BUG: unable to handle page fault for address: ffffea60001db008 CPU: 0 UID: 0 PID: 2199114 Comm: tee Not tainted 6.14.0+ #4 NONE Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014 RIP: 0010:split_huge_pmd_locked+0x3b5/0x2b60 Call Trace: <TASK> try_to_migrate_one+0x28c/0x3730 rmap_walk_anon+0x4f6/0x770 unmap_folio+0x196/0x1f0 split_huge_page_to_list_to_order+0x9f6/0x1560 deferred_split_scan+0xac5/0x12a0 shrinker_debugfs_scan_write+0x376/0x470 full_proxy_write+0x15c/0x220 vfs_write+0x2fc/0xcb0 ksys_write+0x146/0x250 do_syscall_64+0x6a/0x120 entry_SYSCALL_64_after_hwframe+0x76/0x7e The bug is found by syzkaller on an internal kernel, then confirmed on upstream.
02 / AFFECTED SOFTWARE
Affected packages
11 explicit affected versions
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35 explicit affected versions
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74 explicit affected versions
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13 explicit affected versions
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111 explicit affected versions
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10 explicit affected versions
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34 explicit affected versions
81 explicit affected versions
14 explicit affected versions
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11 explicit affected versions
1 explicit affected versions
60 explicit affected versions
115 explicit affected versions
8 explicit affected versions
28 explicit affected versions
62 explicit affected versions
03 / CONNECTIONS
Connected vulnerabilities
04 / EVIDENCE
Source records
In the Linux kernel, the following vulnerability has been resolved: mm/huge_memory: fix dereferencing invalid pmd migration entry When migrating a THP, concurrent access to the PMD migration entry during a deferred split scan can lead to an invalid address access, as illustrated below. To prevent this invalid access, it is necessary to check the PMD migration entry and return early. In this context, there is no need to use pmd_to_swp_entry and pfn_swap_entry_to_page to verify the equality of the target folio. Since the PMD migration entry is locked, it cannot be served as the target. Mailing list discussion and explanation from Hugh Dickins: "An anon_vma lookup points to a location which may contain the folio of interest, but might instead contain another folio: and weeding out those other folios is precisely what the "folio != pmd_folio((*pmd)" check (and the "risk of replacing the wrong folio" comment a few lines above it) is for." BUG: unable to handle page fault for address: ffffea60001db008 CPU: 0 UID: 0 PID: 2199114 Comm: tee Not tainted 6.14.0+ #4 NONE Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014 RIP: 0010:split_huge_pmd_locked+0x3b5/0x2b60 Call Trace: <TASK> try_to_migrate_one+0x28c/0x3730 rmap_walk_anon+0x4f6/0x770 unmap_folio+0x196/0x1f0 split_huge_page_to_list_to_order+0x9f6/0x1560 deferred_split_scan+0xac5/0x12a0 shrinker_debugfs_scan_write+0x376/0x470 full_proxy_write+0x15c/0x220 vfs_write+0x2fc/0xcb0 ksys_write+0x146/0x250 do_syscall_64+0x6a/0x120 entry_SYSCALL_64_after_hwframe+0x76/0x7e The bug is found by syzkaller on an internal kernel, then confirmed on upstream.
05 / REFERENCES
Further evidence
- https://git.kernel.org/linus/be6e843fc51a584672dfd9c4a6a24c8cb81d5fb7
- https://git.kernel.org/stable/c/6166c3cf405441f7147b322980144feb3cefc617
- https://git.kernel.org/stable/c/be6e843fc51a584672dfd9c4a6a24c8cb81d5fb7
- https://git.kernel.org/stable/c/fbab262b0c8226c697af1851a424896ed47dedcc
- https://ubuntu.com/security/CVE-2025-37958
- https://ubuntu.com/security/notices/USN-7699-1
- https://ubuntu.com/security/notices/USN-7699-2
- https://ubuntu.com/security/notices/USN-7721-1
- https://ubuntu.com/security/notices/USN-7774-1
- https://ubuntu.com/security/notices/USN-7774-2
- https://ubuntu.com/security/notices/USN-7774-3
- https://ubuntu.com/security/notices/USN-7774-4
- https://ubuntu.com/security/notices/USN-7774-5
- https://ubuntu.com/security/notices/USN-7775-1
- https://ubuntu.com/security/notices/USN-7775-2
- https://ubuntu.com/security/notices/USN-7775-3
- https://ubuntu.com/security/notices/USN-7776-1
- https://ubuntu.com/security/notices/USN-7907-1
- https://ubuntu.com/security/notices/USN-7907-2
- https://ubuntu.com/security/notices/USN-7907-3
- https://ubuntu.com/security/notices/USN-7907-4
- https://ubuntu.com/security/notices/USN-7907-5
- https://ubuntu.com/security/notices/USN-7922-1
- https://ubuntu.com/security/notices/USN-7922-2
- https://ubuntu.com/security/notices/USN-7922-3
- https://ubuntu.com/security/notices/USN-7922-4
- https://ubuntu.com/security/notices/USN-7922-5
- https://ubuntu.com/security/notices/USN-7931-1
- https://ubuntu.com/security/notices/USN-7931-2
- https://ubuntu.com/security/notices/USN-7931-3
- https://ubuntu.com/security/notices/USN-7931-4
- https://ubuntu.com/security/notices/USN-7931-5
- https://ubuntu.com/security/notices/USN-7935-1
- https://ubuntu.com/security/notices/USN-7937-1
- https://ubuntu.com/security/notices/USN-7939-1
- https://ubuntu.com/security/notices/USN-7939-2
- https://ubuntu.com/security/notices/USN-7940-1
- https://ubuntu.com/security/notices/USN-7940-2
- https://www.cve.org/CVERecord?id=CVE-2025-37958