ghsa-944w-jxg5-jxvw
Vulnerability from github
In the Linux kernel, the following vulnerability has been resolved:
f2fs: fix to do sanity check on sit_bitmap_size
w/ below testcase, resize will generate a corrupted image which contains inconsistent metadata, so when mounting such image, it will trigger kernel panic:
touch img truncate -s $((512102410241024)) img mkfs.f2fs -f img $((25610241024)) resize.f2fs -s -i img -t $((10241024*1024)) mount img /mnt/f2fs
------------[ cut here ]------------ kernel BUG at fs/f2fs/segment.h:863! Oops: invalid opcode: 0000 [#1] SMP PTI CPU: 11 UID: 0 PID: 3922 Comm: mount Not tainted 6.15.0-rc1+ #191 PREEMPT(voluntary) Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014 RIP: 0010:f2fs_ra_meta_pages+0x47c/0x490
Call Trace: f2fs_build_segment_manager+0x11c3/0x2600 f2fs_fill_super+0xe97/0x2840 mount_bdev+0xf4/0x140 legacy_get_tree+0x2b/0x50 vfs_get_tree+0x29/0xd0 path_mount+0x487/0xaf0 __x64_sys_mount+0x116/0x150 do_syscall_64+0x82/0x190 entry_SYSCALL_64_after_hwframe+0x76/0x7e RIP: 0033:0x7fdbfde1bcfe
The reaseon is:
sit_i->bitmap_size is 192, so size of sit bitmap is 192*8=1536, at maximum there are 1536 sit blocks, however MAIN_SEGS is 261893, so that sit_blk_cnt is 4762, build_sit_entries() -> current_sit_addr() tries to access out-of-boundary in sit_bitmap at offset from [1536, 4762), once sit_bitmap and sit_bitmap_mirror is not the same, it will trigger f2fs_bug_on().
Let's add sanity check in f2fs_sanity_check_ckpt() to avoid panic.
{
"affected": [],
"aliases": [
"CVE-2025-38218"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2025-07-04T14:15:30Z",
"severity": null
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\nf2fs: fix to do sanity check on sit_bitmap_size\n\nw/ below testcase, resize will generate a corrupted image which\ncontains inconsistent metadata, so when mounting such image, it\nwill trigger kernel panic:\n\ntouch img\ntruncate -s $((512*1024*1024*1024)) img\nmkfs.f2fs -f img $((256*1024*1024))\nresize.f2fs -s -i img -t $((1024*1024*1024))\nmount img /mnt/f2fs\n\n------------[ cut here ]------------\nkernel BUG at fs/f2fs/segment.h:863!\nOops: invalid opcode: 0000 [#1] SMP PTI\nCPU: 11 UID: 0 PID: 3922 Comm: mount Not tainted 6.15.0-rc1+ #191 PREEMPT(voluntary)\nHardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014\nRIP: 0010:f2fs_ra_meta_pages+0x47c/0x490\n\nCall Trace:\n f2fs_build_segment_manager+0x11c3/0x2600\n f2fs_fill_super+0xe97/0x2840\n mount_bdev+0xf4/0x140\n legacy_get_tree+0x2b/0x50\n vfs_get_tree+0x29/0xd0\n path_mount+0x487/0xaf0\n __x64_sys_mount+0x116/0x150\n do_syscall_64+0x82/0x190\n entry_SYSCALL_64_after_hwframe+0x76/0x7e\nRIP: 0033:0x7fdbfde1bcfe\n\nThe reaseon is:\n\nsit_i-\u003ebitmap_size is 192, so size of sit bitmap is 192*8=1536, at maximum\nthere are 1536 sit blocks, however MAIN_SEGS is 261893, so that sit_blk_cnt\nis 4762, build_sit_entries() -\u003e current_sit_addr() tries to access\nout-of-boundary in sit_bitmap at offset from [1536, 4762), once sit_bitmap\nand sit_bitmap_mirror is not the same, it will trigger f2fs_bug_on().\n\nLet\u0027s add sanity check in f2fs_sanity_check_ckpt() to avoid panic.",
"id": "GHSA-944w-jxg5-jxvw",
"modified": "2025-07-04T15:31:10Z",
"published": "2025-07-04T15:31:09Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2025-38218"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/38ef48a8afef8df646b6f6ae7abb872f18b533c1"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/3e5ac62a56a24f4d88ce8ffd7bc452428b235868"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/5db0d252c64e91ba1929c70112352e85dc5751e7"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/79ef8a6c4ec53d327580fd7d2b522cf4f1d05b0c"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/82f51bff393e4c12cf4de553120ca831cfa4ef19"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/ad862f71016ba38039df1c96ed55c0a4314cc183"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/ee1b421c469876544e297ec1090574bd76100247"
}
],
"schema_version": "1.4.0",
"severity": []
}
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