GHSA-MCQF-M32C-3XWP
Vulnerability from github – Published: 2026-01-14 15:33 – Updated: 2026-01-14 15:33In the Linux kernel, the following vulnerability has been resolved:
ext4: fix string copying in parse_apply_sb_mount_options()
strscpy_pad() can't be used to copy a non-NUL-term string into a NUL-term string of possibly bigger size. Commit 0efc5990bca5 ("string.h: Introduce memtostr() and memtostr_pad()") provides additional information in that regard. So if this happens, the following warning is observed:
strnlen: detected buffer overflow: 65 byte read of buffer size 64 WARNING: CPU: 0 PID: 28655 at lib/string_helpers.c:1032 __fortify_report+0x96/0xc0 lib/string_helpers.c:1032 Modules linked in: CPU: 0 UID: 0 PID: 28655 Comm: syz-executor.3 Not tainted 6.12.54-syzkaller-00144-g5f0270f1ba00 #0 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014 RIP: 0010:__fortify_report+0x96/0xc0 lib/string_helpers.c:1032 Call Trace: __fortify_panic+0x1f/0x30 lib/string_helpers.c:1039 strnlen include/linux/fortify-string.h:235 [inline] sized_strscpy include/linux/fortify-string.h:309 [inline] parse_apply_sb_mount_options fs/ext4/super.c:2504 [inline] __ext4_fill_super fs/ext4/super.c:5261 [inline] ext4_fill_super+0x3c35/0xad00 fs/ext4/super.c:5706 get_tree_bdev_flags+0x387/0x620 fs/super.c:1636 vfs_get_tree+0x93/0x380 fs/super.c:1814 do_new_mount fs/namespace.c:3553 [inline] path_mount+0x6ae/0x1f70 fs/namespace.c:3880 do_mount fs/namespace.c:3893 [inline] __do_sys_mount fs/namespace.c:4103 [inline] __se_sys_mount fs/namespace.c:4080 [inline] __x64_sys_mount+0x280/0x300 fs/namespace.c:4080 do_syscall_x64 arch/x86/entry/common.c:52 [inline] do_syscall_64+0x64/0x140 arch/x86/entry/common.c:83 entry_SYSCALL_64_after_hwframe+0x76/0x7e
Since userspace is expected to provide s_mount_opts field to be at most 63 characters long with the ending byte being NUL-term, use a 64-byte buffer which matches the size of s_mount_opts, so that strscpy_pad() does its job properly. Return with error if the user still managed to provide a non-NUL-term string here.
Found by Linux Verification Center (linuxtesting.org) with Syzkaller.
{
"affected": [],
"aliases": [
"CVE-2025-71123"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-01-14T15:16:02Z",
"severity": null
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\next4: fix string copying in parse_apply_sb_mount_options()\n\nstrscpy_pad() can\u0027t be used to copy a non-NUL-term string into a NUL-term\nstring of possibly bigger size. Commit 0efc5990bca5 (\"string.h: Introduce\nmemtostr() and memtostr_pad()\") provides additional information in that\nregard. So if this happens, the following warning is observed:\n\nstrnlen: detected buffer overflow: 65 byte read of buffer size 64\nWARNING: CPU: 0 PID: 28655 at lib/string_helpers.c:1032 __fortify_report+0x96/0xc0 lib/string_helpers.c:1032\nModules linked in:\nCPU: 0 UID: 0 PID: 28655 Comm: syz-executor.3 Not tainted 6.12.54-syzkaller-00144-g5f0270f1ba00 #0\nHardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014\nRIP: 0010:__fortify_report+0x96/0xc0 lib/string_helpers.c:1032\nCall Trace:\n \u003cTASK\u003e\n __fortify_panic+0x1f/0x30 lib/string_helpers.c:1039\n strnlen include/linux/fortify-string.h:235 [inline]\n sized_strscpy include/linux/fortify-string.h:309 [inline]\n parse_apply_sb_mount_options fs/ext4/super.c:2504 [inline]\n __ext4_fill_super fs/ext4/super.c:5261 [inline]\n ext4_fill_super+0x3c35/0xad00 fs/ext4/super.c:5706\n get_tree_bdev_flags+0x387/0x620 fs/super.c:1636\n vfs_get_tree+0x93/0x380 fs/super.c:1814\n do_new_mount fs/namespace.c:3553 [inline]\n path_mount+0x6ae/0x1f70 fs/namespace.c:3880\n do_mount fs/namespace.c:3893 [inline]\n __do_sys_mount fs/namespace.c:4103 [inline]\n __se_sys_mount fs/namespace.c:4080 [inline]\n __x64_sys_mount+0x280/0x300 fs/namespace.c:4080\n do_syscall_x64 arch/x86/entry/common.c:52 [inline]\n do_syscall_64+0x64/0x140 arch/x86/entry/common.c:83\n entry_SYSCALL_64_after_hwframe+0x76/0x7e\n\nSince userspace is expected to provide s_mount_opts field to be at most 63\ncharacters long with the ending byte being NUL-term, use a 64-byte buffer\nwhich matches the size of s_mount_opts, so that strscpy_pad() does its job\nproperly. Return with error if the user still managed to provide a\nnon-NUL-term string here.\n\nFound by Linux Verification Center (linuxtesting.org) with Syzkaller.",
"id": "GHSA-mcqf-m32c-3xwp",
"modified": "2026-01-14T15:33:01Z",
"published": "2026-01-14T15:33:01Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2025-71123"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/5bbacbbf1ca4419861dca3c6b82707c10e9c021c"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/6e37143560e37869d51b7d9e0ac61fc48895f8a0"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/902ca2356f1e3ec5355c5808ad5d3f9d0095b0cc"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/db9ee13fab0267eccf6544ee35b16c9522db9aac"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/ee5a977b4e771cc181f39d504426dbd31ed701cc"
}
],
"schema_version": "1.4.0",
"severity": []
}
Sightings
| Author | Source | Type | Date |
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