GHSA-QC3F-4C25-G23Q

Vulnerability from github – Published: 2025-05-01 15:31 – Updated: 2025-11-04 18:31
VLAI
Details

In the Linux kernel, the following vulnerability has been resolved:

f2fs: fix to avoid out-of-bounds access in f2fs_truncate_inode_blocks()

syzbot reports an UBSAN issue as below:

------------[ cut here ]------------ UBSAN: array-index-out-of-bounds in fs/f2fs/node.h:381:10 index 18446744073709550692 is out of range for type '__le32[5]' (aka 'unsigned int[5]') CPU: 0 UID: 0 PID: 5318 Comm: syz.0.0 Not tainted 6.14.0-rc3-syzkaller-00060-g6537cfb395f3 #0 Call Trace: __dump_stack lib/dump_stack.c:94 [inline] dump_stack_lvl+0x241/0x360 lib/dump_stack.c:120 ubsan_epilogue lib/ubsan.c:231 [inline] __ubsan_handle_out_of_bounds+0x121/0x150 lib/ubsan.c:429 get_nid fs/f2fs/node.h:381 [inline] f2fs_truncate_inode_blocks+0xa5e/0xf60 fs/f2fs/node.c:1181 f2fs_do_truncate_blocks+0x782/0x1030 fs/f2fs/file.c:808 f2fs_truncate_blocks+0x10d/0x300 fs/f2fs/file.c:836 f2fs_truncate+0x417/0x720 fs/f2fs/file.c:886 f2fs_file_write_iter+0x1bdb/0x2550 fs/f2fs/file.c:5093 aio_write+0x56b/0x7c0 fs/aio.c:1633 io_submit_one+0x8a7/0x18a0 fs/aio.c:2052 __do_sys_io_submit fs/aio.c:2111 [inline] __se_sys_io_submit+0x171/0x2e0 fs/aio.c:2081 do_syscall_x64 arch/x86/entry/common.c:52 [inline] do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f238798cde9

index 18446744073709550692 (decimal, unsigned long long) = 0xfffffffffffffc64 (hexadecimal, unsigned long long) = -924 (decimal, long long)

In f2fs_truncate_inode_blocks(), UBSAN detects that get_nid() tries to access .i_nid[-924], it means both offset[0] and level should zero.

The possible case should be in f2fs_do_truncate_blocks(), we try to truncate inode size to zero, however, dn.ofs_in_node is zero and dn.node_page is not an inode page, so it fails to truncate inode page, and then pass zeroed free_from to f2fs_truncate_inode_blocks(), result in this issue.

if (dn.ofs_in_node || IS_INODE(dn.node_page)) {
    f2fs_truncate_data_blocks_range(&dn, count);
    free_from += count;
}

I guess the reason why dn.node_page is not an inode page could be: there are multiple nat entries share the same node block address, once the node block address was reused, f2fs_get_node_page() may load a non-inode block.

Let's add a sanity check for such condition to avoid out-of-bounds access issue.

Severity
7.1 (High)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H
Show details on source website
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{
  "affected": [],
  "aliases": [
    "CVE-2025-37739"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-125"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2025-05-01T13:15:52Z",
    "severity": "HIGH"
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nf2fs: fix to avoid out-of-bounds access in f2fs_truncate_inode_blocks()\n\nsyzbot reports an UBSAN issue as below:\n\n------------[ cut here ]------------\nUBSAN: array-index-out-of-bounds in fs/f2fs/node.h:381:10\nindex 18446744073709550692 is out of range for type \u0027__le32[5]\u0027 (aka \u0027unsigned int[5]\u0027)\nCPU: 0 UID: 0 PID: 5318 Comm: syz.0.0 Not tainted 6.14.0-rc3-syzkaller-00060-g6537cfb395f3 #0\nCall Trace:\n \u003cTASK\u003e\n __dump_stack lib/dump_stack.c:94 [inline]\n dump_stack_lvl+0x241/0x360 lib/dump_stack.c:120\n ubsan_epilogue lib/ubsan.c:231 [inline]\n __ubsan_handle_out_of_bounds+0x121/0x150 lib/ubsan.c:429\n get_nid fs/f2fs/node.h:381 [inline]\n f2fs_truncate_inode_blocks+0xa5e/0xf60 fs/f2fs/node.c:1181\n f2fs_do_truncate_blocks+0x782/0x1030 fs/f2fs/file.c:808\n f2fs_truncate_blocks+0x10d/0x300 fs/f2fs/file.c:836\n f2fs_truncate+0x417/0x720 fs/f2fs/file.c:886\n f2fs_file_write_iter+0x1bdb/0x2550 fs/f2fs/file.c:5093\n aio_write+0x56b/0x7c0 fs/aio.c:1633\n io_submit_one+0x8a7/0x18a0 fs/aio.c:2052\n __do_sys_io_submit fs/aio.c:2111 [inline]\n __se_sys_io_submit+0x171/0x2e0 fs/aio.c:2081\n do_syscall_x64 arch/x86/entry/common.c:52 [inline]\n do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83\n entry_SYSCALL_64_after_hwframe+0x77/0x7f\nRIP: 0033:0x7f238798cde9\n\nindex 18446744073709550692 (decimal, unsigned long long)\n= 0xfffffffffffffc64 (hexadecimal, unsigned long long)\n= -924 (decimal, long long)\n\nIn f2fs_truncate_inode_blocks(), UBSAN detects that get_nid() tries to\naccess .i_nid[-924], it means both offset[0] and level should zero.\n\nThe possible case should be in f2fs_do_truncate_blocks(), we try to\ntruncate inode size to zero, however, dn.ofs_in_node is zero and\ndn.node_page is not an inode page, so it fails to truncate inode page,\nand then pass zeroed free_from to f2fs_truncate_inode_blocks(), result\nin this issue.\n\n\tif (dn.ofs_in_node || IS_INODE(dn.node_page)) {\n\t\tf2fs_truncate_data_blocks_range(\u0026dn, count);\n\t\tfree_from += count;\n\t}\n\nI guess the reason why dn.node_page is not an inode page could be: there\nare multiple nat entries share the same node block address, once the node\nblock address was reused, f2fs_get_node_page() may load a non-inode block.\n\nLet\u0027s add a sanity check for such condition to avoid out-of-bounds access\nissue.",
  "id": "GHSA-qc3f-4c25-g23q",
  "modified": "2025-11-04T18:31:32Z",
  "published": "2025-05-01T15:31:42Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2025-37739"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/67e16ccba74dd8de0a7b10062f1e02d77432f573"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/6ba8b41d0aa4b82f90f0c416cb53fcef9696525d"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/8b5e5aac44fee122947a269f9034c048e4c295de"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/98dbf2af63de0b551082c9bc48333910e009b09f"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/a67e1bf03c609a751d1740a1789af25e599966fa"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/d7242fd7946d4cba0411effb6b5048ca55125747"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/e6494977bd4a83862118a05f57a8df40256951c0"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/ecc461331604b07cdbdb7360dbdf78471653264c"
    },
    {
      "type": "WEB",
      "url": "https://lists.debian.org/debian-lts-announce/2025/05/msg00030.html"
    },
    {
      "type": "WEB",
      "url": "https://lists.debian.org/debian-lts-announce/2025/05/msg00045.html"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H",
      "type": "CVSS_V3"
    }
  ]
}



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