ghsa-2xf6-75gh-3848
Vulnerability from github
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.
{
"affected": [],
"aliases": [
"CVE-2025-40054"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2025-10-28T12:15:39Z",
"severity": null
},
"details": "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.",
"id": "GHSA-2xf6-75gh-3848",
"modified": "2025-10-28T12:30:17Z",
"published": "2025-10-28T12:30:16Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2025-40054"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/01118321e0c8a5f3ece57d0d377bfc92d83cd210"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/edf7e9040fc52c922db947f9c6c36f07377c52ea"
}
],
"schema_version": "1.4.0",
"severity": []
}
Sightings
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