CVE-2026-23375 (GCVE-0-2026-23375)

Vulnerability from cvelistv5 – Published: 2026-03-25 10:27 – Updated: 2026-04-13 06:06
VLAI?
Title
mm: thp: deny THP for files on anonymous inodes
Summary
In the Linux kernel, the following vulnerability has been resolved: mm: thp: deny THP for files on anonymous inodes file_thp_enabled() incorrectly allows THP for files on anonymous inodes (e.g. guest_memfd and secretmem). These files are created via alloc_file_pseudo(), which does not call get_write_access() and leaves inode->i_writecount at 0. Combined with S_ISREG(inode->i_mode) being true, they appear as read-only regular files when CONFIG_READ_ONLY_THP_FOR_FS is enabled, making them eligible for THP collapse. Anonymous inodes can never pass the inode_is_open_for_write() check since their i_writecount is never incremented through the normal VFS open path. The right thing to do is to exclude them from THP eligibility altogether, since CONFIG_READ_ONLY_THP_FOR_FS was designed for real filesystem files (e.g. shared libraries), not for pseudo-filesystem inodes. For guest_memfd, this allows khugepaged and MADV_COLLAPSE to create large folios in the page cache via the collapse path, but the guest_memfd fault handler does not support large folios. This triggers WARN_ON_ONCE(folio_test_large(folio)) in kvm_gmem_fault_user_mapping(). For secretmem, collapse_file() tries to copy page contents through the direct map, but secretmem pages are removed from the direct map. This can result in a kernel crash: BUG: unable to handle page fault for address: ffff88810284d000 RIP: 0010:memcpy_orig+0x16/0x130 Call Trace: collapse_file hpage_collapse_scan_file madvise_collapse Secretmem is not affected by the crash on upstream as the memory failure recovery handles the failed copy gracefully, but it still triggers confusing false memory failure reports: Memory failure: 0x106d96f: recovery action for clean unevictable LRU page: Recovered Check IS_ANON_FILE(inode) in file_thp_enabled() to deny THP for all anonymous inode files.
Severity ?
No CVSS data available.
Assigner
References
Impacted products
Vendor Product Version
Linux Linux Affected: 7fbb5e188248c50f737720825da1864ce42536d1 , < 08de46a75f91a6661bc1ce0a93614f4bc313c581 (git)
Affected: 7fbb5e188248c50f737720825da1864ce42536d1 , < 0524ee56af2c9bfbad152a810f1ca95de8ca00d7 (git)
Affected: 7fbb5e188248c50f737720825da1864ce42536d1 , < f6fa05f0dddd387417d0c28281ddb951582514d6 (git)
Affected: 7fbb5e188248c50f737720825da1864ce42536d1 , < dd085fe9a8ebfc5d10314c60452db38d2b75e609 (git)
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    Linux Linux Affected: 6.8
Unaffected: 0 , < 6.8 (semver)
Unaffected: 6.12.78 , ≤ 6.12.* (semver)
Unaffected: 6.18.17 , ≤ 6.18.* (semver)
Unaffected: 6.19.7 , ≤ 6.19.* (semver)
Unaffected: 7.0 , ≤ * (original_commit_for_fix)
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          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nmm: thp: deny THP for files on anonymous inodes\n\nfile_thp_enabled() incorrectly allows THP for files on anonymous inodes\n(e.g. guest_memfd and secretmem). These files are created via\nalloc_file_pseudo(), which does not call get_write_access() and leaves\ninode-\u003ei_writecount at 0. Combined with S_ISREG(inode-\u003ei_mode) being\ntrue, they appear as read-only regular files when\nCONFIG_READ_ONLY_THP_FOR_FS is enabled, making them eligible for THP\ncollapse.\n\nAnonymous inodes can never pass the inode_is_open_for_write() check\nsince their i_writecount is never incremented through the normal VFS\nopen path. The right thing to do is to exclude them from THP eligibility\naltogether, since CONFIG_READ_ONLY_THP_FOR_FS was designed for real\nfilesystem files (e.g. shared libraries), not for pseudo-filesystem\ninodes.\n\nFor guest_memfd, this allows khugepaged and MADV_COLLAPSE to create\nlarge folios in the page cache via the collapse path, but the\nguest_memfd fault handler does not support large folios. This triggers\nWARN_ON_ONCE(folio_test_large(folio)) in kvm_gmem_fault_user_mapping().\n\nFor secretmem, collapse_file() tries to copy page contents through the\ndirect map, but secretmem pages are removed from the direct map. This\ncan result in a kernel crash:\n\n    BUG: unable to handle page fault for address: ffff88810284d000\n    RIP: 0010:memcpy_orig+0x16/0x130\n    Call Trace:\n     collapse_file\n     hpage_collapse_scan_file\n     madvise_collapse\n\nSecretmem is not affected by the crash on upstream as the memory failure\nrecovery handles the failed copy gracefully, but it still triggers\nconfusing false memory failure reports:\n\n    Memory failure: 0x106d96f: recovery action for clean unevictable\n    LRU page: Recovered\n\nCheck IS_ANON_FILE(inode) in file_thp_enabled() to deny THP for all\nanonymous inode files."
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This\\ncan result in a kernel crash:\\n\\n    BUG: unable to handle page fault for address: ffff88810284d000\\n    RIP: 0010:memcpy_orig+0x16/0x130\\n    Call Trace:\\n     collapse_file\\n     hpage_collapse_scan_file\\n     madvise_collapse\\n\\nSecretmem is not affected by the crash on upstream as the memory failure\\nrecovery handles the failed copy gracefully, but it still triggers\\nconfusing false memory failure reports:\\n\\n    Memory failure: 0x106d96f: recovery action for clean unevictable\\n    LRU page: Recovered\\n\\nCheck IS_ANON_FILE(inode) in file_thp_enabled() to deny THP for all\\nanonymous inode files.\"},{\"lang\":\"es\",\"value\":\"En el kernel de Linux, la siguiente vulnerabilidad ha sido resuelta:\\n\\nmm: thp: denegar THP para archivos en inodos an\u00f3nimos\\n\\nfile_thp_enabled() permite incorrectamente THP para archivos en inodos an\u00f3nimos (por ejemplo, guest_memfd y secretmem). 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  }
}


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  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
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  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.



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