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vuln-cve/data/2025/40xxx/CVE-2025-40054.json
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{
"dataType": "CVE_RECORD",
"dataVersion": "5.2",
"cveMetadata": {
"cveId": "CVE-2025-40054",
"assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"state": "PUBLISHED",
"assignerShortName": "Linux",
"dateReserved": "2025-04-16T07:20:57.157Z",
"datePublished": "2025-10-28T11:48:29.073Z",
"dateUpdated": "2026-08-23T12:45:24.871Z"
},
"containers": {
"cna": {
"providerMetadata": {
"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"shortName": "Linux",
"dateUpdated": "2026-08-23T12:45:24.871Z"
},
"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 & cache bio in\n io->bio_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->bio_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->encrypted_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>0;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>0;i++)) do xfs_io -f /mnt/f2fs/enc/file \\\n-c \"pwrite 0 32k\" -c \"fdatasync\"\n\nSo, in f2fs_merge_page_bio(), let's avoid using fio->encrypted_page after\ncommit page into internal ipu cache."
}
],
"metrics": [
{
"cvssV3_1": {
"version": "3.1",
"vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
"baseScore": 7.8,
"baseSeverity": "HIGH"
},
"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 — one thread's writeback caches the encrypted bounce page in the IPU bio list while a second thread's f2fs_write_begin → f2fs_folio_wait_writeback submits that same bio and frees the bounce page — 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 — the attacker's 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's 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->nr_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."
}
]
}
],
"affected": [
{
"product": "Linux",
"vendor": "Linux",
"defaultStatus": "unaffected",
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"programFiles": [
"fs/f2fs/data.c"
],
"versions": [
{
"version": "0b20fcec8651569935a10afe03fedc0b812d044e",
"lessThan": "1f7b44b4a2b2939f08b279cbb9e6b5dcb8ffea32",
"status": "affected",
"versionType": "git"
},
{
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"lessThan": "e193d8953647c8b575830852aa5ea0995b98d2b1",
"status": "affected",
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},
{
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"status": "affected",
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},
{
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"lessThan": "68e094232dfe5027c4fd2dcded93d2d6800bae04",
"status": "affected",
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{
"version": "0b20fcec8651569935a10afe03fedc0b812d044e",
"lessThan": "7dd611131d82d7fc4212b555eb1103160bdad302",
"status": "affected",
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},
{
"version": "0b20fcec8651569935a10afe03fedc0b812d044e",
"lessThan": "01118321e0c8a5f3ece57d0d377bfc92d83cd210",
"status": "affected",
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},
{
"version": "0b20fcec8651569935a10afe03fedc0b812d044e",
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"status": "affected",
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}
]
},
{
"product": "Linux",
"vendor": "Linux",
"defaultStatus": "affected",
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"programFiles": [
"fs/f2fs/data.c"
],
"versions": [
{
"version": "5.5",
"status": "affected"
},
{
"version": "0",
"lessThan": "5.5",
"status": "unaffected",
"versionType": "semver"
},
{
"version": "5.10.266",
"lessThanOrEqual": "5.10.*",
"status": "unaffected",
"versionType": "semver"
},
{
"version": "5.15.217",
"lessThanOrEqual": "5.15.*",
"status": "unaffected",
"versionType": "semver"
},
{
"version": "6.1.184",
"lessThanOrEqual": "6.1.*",
"status": "unaffected",
"versionType": "semver"
},
{
"version": "6.6.153",
"lessThanOrEqual": "6.6.*",
"status": "unaffected",
"versionType": "semver"
},
{
"version": "6.12.105",
"lessThanOrEqual": "6.12.*",
"status": "unaffected",
"versionType": "semver"
},
{
"version": "6.17.3",
"lessThanOrEqual": "6.17.*",
"status": "unaffected",
"versionType": "semver"
},
{
"version": "6.18",
"lessThanOrEqual": "*",
"status": "unaffected",
"versionType": "original_commit_for_fix"
}
]
}
],
"cpeApplicability": [
{
"nodes": [
{
"operator": "OR",
"negate": false,
"cpeMatch": [
{
"vulnerable": true,
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionStartIncluding": "5.5",
"versionEndExcluding": "5.10.266"
},
{
"vulnerable": true,
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionStartIncluding": "5.5",
"versionEndExcluding": "5.15.217"
},
{
"vulnerable": true,
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionStartIncluding": "5.5",
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},
{
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"versionStartIncluding": "5.5",
"versionEndExcluding": "6.6.153"
},
{
"vulnerable": true,
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionStartIncluding": "5.5",
"versionEndExcluding": "6.12.105"
},
{
"vulnerable": true,
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionStartIncluding": "5.5",
"versionEndExcluding": "6.17.3"
},
{
"vulnerable": true,
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionStartIncluding": "5.5",
"versionEndExcluding": "6.18"
}
]
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}
],
"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"
}
}
}
}
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