CVE-2025-40054 (GCVE-0-2025-40054)
Vulnerability from cvelistv5
Published
2025-10-28 11:48
Modified
2026-08-23 12:45
Severity ?
7.8 (High) - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: f2fs: fix UAF issue in f2fs_merge_page_bio() As JY reported in bugzilla [1], Unable to handle kernel NULL pointer dereference at virtual address 0000000000000000 pc : [0xffffffe51d249484] f2fs_is_cp_guaranteed+0x70/0x98 lr : [0xffffffe51d24adbc] f2fs_merge_page_bio+0x520/0x6d4 CPU: 3 UID: 0 PID: 6790 Comm: kworker/u16:3 Tainted: P B W OE 6.12.30-android16-5-maybe-dirty-4k #1 5f7701c9cbf727d1eebe77c89bbbeb3371e895e5 Tainted: [P]=PROPRIETARY_MODULE, [B]=BAD_PAGE, [W]=WARN, [O]=OOT_MODULE, [E]=UNSIGNED_MODULE Workqueue: writeback wb_workfn (flush-254:49) Call trace: f2fs_is_cp_guaranteed+0x70/0x98 f2fs_inplace_write_data+0x174/0x2f4 f2fs_do_write_data_page+0x214/0x81c f2fs_write_single_data_page+0x28c/0x764 f2fs_write_data_pages+0x78c/0xce4 do_writepages+0xe8/0x2fc __writeback_single_inode+0x4c/0x4b4 writeback_sb_inodes+0x314/0x540 __writeback_inodes_wb+0xa4/0xf4 wb_writeback+0x160/0x448 wb_workfn+0x2f0/0x5dc process_scheduled_works+0x1c8/0x458 worker_thread+0x334/0x3f0 kthread+0x118/0x1ac ret_from_fork+0x10/0x20 [1] https://bugzilla.kernel.org/show_bug.cgi?id=220575 The panic was caused by UAF issue w/ below race condition: kworker - writepages - f2fs_write_cache_pages - f2fs_write_single_data_page - f2fs_do_write_data_page - f2fs_inplace_write_data - f2fs_merge_page_bio - add_inu_page : cache page #1 into bio & cache bio in io->bio_list - f2fs_write_single_data_page - f2fs_do_write_data_page - f2fs_inplace_write_data - f2fs_merge_page_bio - add_inu_page : cache page #2 into bio which is linked in io->bio_list write - f2fs_write_begin : write page #1 - f2fs_folio_wait_writeback - f2fs_submit_merged_ipu_write - f2fs_submit_write_bio : submit bio which inclues page #1 and #2 software IRQ - f2fs_write_end_io - fscrypt_free_bounce_page : freed bounced page which belongs to page #2 - inc_page_count( , WB_DATA_TYPE(data_folio), false) : data_folio points to fio->encrypted_page the bounced page can be freed before accessing it in f2fs_is_cp_guarantee() It can reproduce w/ below testcase: Run below script in shell #1: for ((i=1;i>0;i++)) do xfs_io -f /mnt/f2fs/enc/file \ -c "pwrite 0 32k" -c "fdatasync" Run below script in shell #2: for ((i=1;i>0;i++)) do xfs_io -f /mnt/f2fs/enc/file \ -c "pwrite 0 32k" -c "fdatasync" So, in f2fs_merge_page_bio(), let's avoid using fio->encrypted_page after commit page into internal ipu cache.
References
Impacted products
Vendor Product Version
Linux Linux Version: 0b20fcec8651569935a10afe03fedc0b812d044e
Version: 0b20fcec8651569935a10afe03fedc0b812d044e
Version: 0b20fcec8651569935a10afe03fedc0b812d044e
Version: 0b20fcec8651569935a10afe03fedc0b812d044e
Version: 0b20fcec8651569935a10afe03fedc0b812d044e
Version: 0b20fcec8651569935a10afe03fedc0b812d044e
Version: 0b20fcec8651569935a10afe03fedc0b812d044e
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{
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          "programFiles": [
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              "version": "6.17.3",
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              "versionType": "original_commit_for_fix"
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      "cpeApplicability": [
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              "negate": false,
              "operator": "OR"
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          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nf2fs: fix UAF issue in f2fs_merge_page_bio()\n\nAs JY reported in bugzilla [1],\n\nUnable to handle kernel NULL pointer dereference at virtual address 0000000000000000\npc : [0xffffffe51d249484] f2fs_is_cp_guaranteed+0x70/0x98\nlr : [0xffffffe51d24adbc] f2fs_merge_page_bio+0x520/0x6d4\nCPU: 3 UID: 0 PID: 6790 Comm: kworker/u16:3 Tainted: P    B   W  OE      6.12.30-android16-5-maybe-dirty-4k #1 5f7701c9cbf727d1eebe77c89bbbeb3371e895e5\nTainted: [P]=PROPRIETARY_MODULE, [B]=BAD_PAGE, [W]=WARN, [O]=OOT_MODULE, [E]=UNSIGNED_MODULE\nWorkqueue: writeback wb_workfn (flush-254:49)\nCall trace:\n f2fs_is_cp_guaranteed+0x70/0x98\n f2fs_inplace_write_data+0x174/0x2f4\n f2fs_do_write_data_page+0x214/0x81c\n f2fs_write_single_data_page+0x28c/0x764\n f2fs_write_data_pages+0x78c/0xce4\n do_writepages+0xe8/0x2fc\n __writeback_single_inode+0x4c/0x4b4\n writeback_sb_inodes+0x314/0x540\n __writeback_inodes_wb+0xa4/0xf4\n wb_writeback+0x160/0x448\n wb_workfn+0x2f0/0x5dc\n process_scheduled_works+0x1c8/0x458\n worker_thread+0x334/0x3f0\n kthread+0x118/0x1ac\n ret_from_fork+0x10/0x20\n\n[1] https://bugzilla.kernel.org/show_bug.cgi?id=220575\n\nThe panic was caused by UAF issue w/ below race condition:\n\nkworker\n- writepages\n - f2fs_write_cache_pages\n  - f2fs_write_single_data_page\n   - f2fs_do_write_data_page\n    - f2fs_inplace_write_data\n     - f2fs_merge_page_bio\n      - add_inu_page\n      : cache page #1 into bio \u0026 cache bio in\n        io-\u003ebio_list\n  - f2fs_write_single_data_page\n   - f2fs_do_write_data_page\n    - f2fs_inplace_write_data\n     - f2fs_merge_page_bio\n      - add_inu_page\n      : cache page #2 into bio which is linked\n        in io-\u003ebio_list\n\t\t\t\t\t\twrite\n\t\t\t\t\t\t- f2fs_write_begin\n\t\t\t\t\t\t: write page #1\n\t\t\t\t\t\t - f2fs_folio_wait_writeback\n\t\t\t\t\t\t  - f2fs_submit_merged_ipu_write\n\t\t\t\t\t\t   - f2fs_submit_write_bio\n\t\t\t\t\t\t   : submit bio which inclues page #1 and #2\n\n\t\t\t\t\t\tsoftware IRQ\n\t\t\t\t\t\t- f2fs_write_end_io\n\t\t\t\t\t\t - fscrypt_free_bounce_page\n\t\t\t\t\t\t : freed bounced page which belongs to page #2\n      - inc_page_count( , WB_DATA_TYPE(data_folio), false)\n      : data_folio points to fio-\u003eencrypted_page\n        the bounced page can be freed before\n        accessing it in f2fs_is_cp_guarantee()\n\nIt can reproduce w/ below testcase:\nRun below script in shell #1:\nfor ((i=1;i\u003e0;i++)) do xfs_io -f /mnt/f2fs/enc/file \\\n-c \"pwrite 0 32k\" -c \"fdatasync\"\n\nRun below script in shell #2:\nfor ((i=1;i\u003e0;i++)) do xfs_io -f /mnt/f2fs/enc/file \\\n-c \"pwrite 0 32k\" -c \"fdatasync\"\n\nSo, in f2fs_merge_page_bio(), let\u0027s avoid using fio-\u003eencrypted_page after\ncommit page into internal ipu cache."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 7.8,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:L - The bug is reached through ordinary local filesystem syscalls (write/pwrite plus fdatasync) on a mounted f2fs volume, driving the writeback kworker into f2fs_merge_page_bio(); no network or remote peer data is involved.\nAC:L - The attacker controls both sides of the race \u2014 one thread\u0027s writeback caches the encrypted bounce page in the IPU bio list while a second thread\u0027s f2fs_write_begin \u2192 f2fs_folio_wait_writeback submits that same bio and frees the bounce page \u2014 and the commit supplies a trivial two-shell reproducer loop, so it can be hit reliably by repetition.\nPR:L - Only an unprivileged local user with write access to a file in an fscrypt-encrypted directory on f2fs is needed; this is the default state for every app on Android/ChromeOS f2fs /data, and elsewhere any user can set a v2 encryption policy on their own directory without CAP_SYS_ADMIN.\nUI:N - No victim action is required \u2014 the attacker\u0027s own two processes perform all writes and syncs against an already-mounted filesystem, and the racing writeback kworker runs automatically.\nS:U - The freed object, the corrupted accounting counters and the faulting code all live within the kernel\u0027s own security authority; no VM, IOMMU or sandbox boundary is crossed.\nC:H - This is a use-after-free read of a freed fscrypt bounce-page descriptor whose contents are reused by whatever next owns that page, and the stale pointer read from it is dereferenced, giving an attacker-influenceable wild read of kernel memory that leaks into observable filesystem accounting state.\nI:H - Use-after-free of a mempool page that can be recycled into arbitrary kernel allocations makes heap grooming and control over the dereferenced pointer feasible, and the garbage value directly corrupts persistent sbi-\u003enr_pages writeback accounting, wedging checkpoint state machine decisions such as f2fs_stop_checkpoint.\nA:H - The bug is confirmed in the wild to panic the kernel with a NULL pointer dereference in f2fs_is_cp_guaranteed() from the writeback kworker, and a mismatched WB_DATA_TYPE increment leaves F2FS_WB_CP_DATA permanently non-zero, hanging f2fs_wait_on_all_pages() in an uninterruptible loop so sync/umount never complete."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-23T12:45:24.871Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/1f7b44b4a2b2939f08b279cbb9e6b5dcb8ffea32"
        },
        {
          "url": "https://git.kernel.org/stable/c/e193d8953647c8b575830852aa5ea0995b98d2b1"
        },
        {
          "url": "https://git.kernel.org/stable/c/410337c2301ae78a081e1b5ebbe8ec374fef4cb6"
        },
        {
          "url": "https://git.kernel.org/stable/c/68e094232dfe5027c4fd2dcded93d2d6800bae04"
        },
        {
          "url": "https://git.kernel.org/stable/c/7dd611131d82d7fc4212b555eb1103160bdad302"
        },
        {
          "url": "https://git.kernel.org/stable/c/01118321e0c8a5f3ece57d0d377bfc92d83cd210"
        },
        {
          "url": "https://git.kernel.org/stable/c/edf7e9040fc52c922db947f9c6c36f07377c52ea"
        }
      ],
      "title": "f2fs: fix UAF issue in f2fs_merge_page_bio()",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2025-40054",
    "datePublished": "2025-10-28T11:48:29.073Z",
    "dateReserved": "2025-04-16T07:20:57.157Z",
    "dateUpdated": "2026-08-23T12:45:24.871Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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