CVE-2025-71123

In the Linux kernel, the following vulnerability has been resolved:<br /> <br /> ext4: fix string copying in parse_apply_sb_mount_options()<br /> <br /> strscpy_pad() can&amp;#39;t be used to copy a non-NUL-term string into a NUL-term<br /> string of possibly bigger size. Commit 0efc5990bca5 ("string.h: Introduce<br /> memtostr() and memtostr_pad()") provides additional information in that<br /> regard. So if this happens, the following warning is observed:<br /> <br /> strnlen: detected buffer overflow: 65 byte read of buffer size 64<br /> WARNING: CPU: 0 PID: 28655 at lib/string_helpers.c:1032 __fortify_report+0x96/0xc0 lib/string_helpers.c:1032<br /> Modules linked in:<br /> CPU: 0 UID: 0 PID: 28655 Comm: syz-executor.3 Not tainted 6.12.54-syzkaller-00144-g5f0270f1ba00 #0<br /> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014<br /> RIP: 0010:__fortify_report+0x96/0xc0 lib/string_helpers.c:1032<br /> Call Trace:<br /> <br /> __fortify_panic+0x1f/0x30 lib/string_helpers.c:1039<br /> strnlen include/linux/fortify-string.h:235 [inline]<br /> sized_strscpy include/linux/fortify-string.h:309 [inline]<br /> parse_apply_sb_mount_options fs/ext4/super.c:2504 [inline]<br /> __ext4_fill_super fs/ext4/super.c:5261 [inline]<br /> ext4_fill_super+0x3c35/0xad00 fs/ext4/super.c:5706<br /> get_tree_bdev_flags+0x387/0x620 fs/super.c:1636<br /> vfs_get_tree+0x93/0x380 fs/super.c:1814<br /> do_new_mount fs/namespace.c:3553 [inline]<br /> path_mount+0x6ae/0x1f70 fs/namespace.c:3880<br /> do_mount fs/namespace.c:3893 [inline]<br /> __do_sys_mount fs/namespace.c:4103 [inline]<br /> __se_sys_mount fs/namespace.c:4080 [inline]<br /> __x64_sys_mount+0x280/0x300 fs/namespace.c:4080<br /> do_syscall_x64 arch/x86/entry/common.c:52 [inline]<br /> do_syscall_64+0x64/0x140 arch/x86/entry/common.c:83<br /> entry_SYSCALL_64_after_hwframe+0x76/0x7e<br /> <br /> Since userspace is expected to provide s_mount_opts field to be at most 63<br /> characters long with the ending byte being NUL-term, use a 64-byte buffer<br /> which matches the size of s_mount_opts, so that strscpy_pad() does its job<br /> properly. Return with error if the user still managed to provide a<br /> non-NUL-term string here.<br /> <br /> Found by Linux Verification Center (linuxtesting.org) with Syzkaller.