[syzbot] [xfs?] KMSAN: uninit-value in xlog_verify_head

syzbot
2026-04-02T18:55:22Z

Hello,

syzbot found the following issue on:

HEAD commit: cbfffcca2bf0 Merge tag 'trace-v7.0-rc5' of git://git.kerne..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=13b5ff52580000
kernel config: https://syzkaller.appspot.com/x/.config?x=963de479f54c6dbb
dashboard link: https://syzkaller.appspot.com/bug?extid=b7dfbed0c6c2b5e9fd34
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
userspace arch: i386

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/b6db7d9b793c/disk-cbfffcca.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/027636820b95/vmlinux-cbfffcca.xz
kernel image: https://storage.googleapis.com/syzbot-assets/b7d1a553de59/bzImage-cbfffcca.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+b7dfbed0c6c2b5e9fd34@syzkaller.appspotmail.com

XFS (loop4): Mounting V5 Filesystem d7dc424e-7990-42cb-9f91-9cb7200a101d
=====================================================
BUG: KMSAN: uninit-value in xlog_verify_head+0x6c3/0x910 fs/xfs/xfs_log_recover.c:1058
xlog_verify_head+0x6c3/0x910 fs/xfs/xfs_log_recover.c:1058
xlog_find_tail+0xc2e/0x1a50 fs/xfs/xfs_log_recover.c:1315
xlog_recover+0x6d/0x800 fs/xfs/xfs_log_recover.c:3426
xfs_log_mount+0x4da/0x880 fs/xfs/xfs_log.c:617
xfs_mountfs+0x1599/0x2d00 fs/xfs/xfs_mount.c:1034
xfs_fs_fill_super+0x2603/0x2be0 fs/xfs/xfs_super.c:1938
get_tree_bdev_flags+0x6e6/0x920 fs/super.c:1694
get_tree_bdev+0x38/0x50 fs/super.c:1717
xfs_fs_get_tree+0x35/0x40 fs/xfs/xfs_super.c:1985
vfs_get_tree+0xb3/0x5d0 fs/super.c:1754
fc_mount fs/namespace.c:1193 [inline]
do_new_mount_fc fs/namespace.c:3763 [inline]
do_new_mount+0x885/0x1dd0 fs/namespace.c:3839
path_mount+0x7a2/0x20b0 fs/namespace.c:4159
do_mount fs/namespace.c:4172 [inline]
__do_sys_mount fs/namespace.c:4361 [inline]
__se_sys_mount+0x704/0x7f0 fs/namespace.c:4338
__ia32_sys_mount+0xe2/0x150 fs/namespace.c:4338
ia32_sys_call+0x27fe/0x4360 arch/x86/include/generated/asm/syscalls_32.h:22
do_syscall_32_irqs_on arch/x86/entry/syscall_32.c:83 [inline]
__do_fast_syscall_32+0x17f/0x3f0 arch/x86/entry/syscall_32.c:307
do_fast_syscall_32+0x37/0x80 arch/x86/entry/syscall_32.c:332
do_SYSENTER_32+0x1f/0x30 arch/x86/entry/syscall_32.c:370
entry_SYSENTER_compat_after_hwframe+0x84/0x8e

Uninit was stored to memory at:
xlog_verify_head+0x6bc/0x910 fs/xfs/xfs_log_recover.c:1058
xlog_find_tail+0xc2e/0x1a50 fs/xfs/xfs_log_recover.c:1315
xlog_recover+0x6d/0x800 fs/xfs/xfs_log_recover.c:3426
xfs_log_mount+0x4da/0x880 fs/xfs/xfs_log.c:617
xfs_mountfs+0x1599/0x2d00 fs/xfs/xfs_mount.c:1034
xfs_fs_fill_super+0x2603/0x2be0 fs/xfs/xfs_super.c:1938
get_tree_bdev_flags+0x6e6/0x920 fs/super.c:1694
get_tree_bdev+0x38/0x50 fs/super.c:1717
xfs_fs_get_tree+0x35/0x40 fs/xfs/xfs_super.c:1985
vfs_get_tree+0xb3/0x5d0 fs/super.c:1754
fc_mount fs/namespace.c:1193 [inline]
do_new_mount_fc fs/namespace.c:3763 [inline]
do_new_mount+0x885/0x1dd0 fs/namespace.c:3839
path_mount+0x7a2/0x20b0 fs/namespace.c:4159
do_mount fs/namespace.c:4172 [inline]
__do_sys_mount fs/namespace.c:4361 [inline]
__se_sys_mount+0x704/0x7f0 fs/namespace.c:4338
__ia32_sys_mount+0xe2/0x150 fs/namespace.c:4338
ia32_sys_call+0x27fe/0x4360 arch/x86/include/generated/asm/syscalls_32.h:22
do_syscall_32_irqs_on arch/x86/entry/syscall_32.c:83 [inline]
__do_fast_syscall_32+0x17f/0x3f0 arch/x86/entry/syscall_32.c:307
do_fast_syscall_32+0x37/0x80 arch/x86/entry/syscall_32.c:332
do_SYSENTER_32+0x1f/0x30 arch/x86/entry/syscall_32.c:370
entry_SYSENTER_compat_after_hwframe+0x84/0x8e

Local variable tmp_rhead_blk created at:
xlog_verify_head+0x81/0x910 fs/xfs/xfs_log_recover.c:1032
xlog_find_tail+0xc2e/0x1a50 fs/xfs/xfs_log_recover.c:1315

CPU: 1 UID: 0 PID: 7664 Comm: syz.4.285 Tainted: G L syzkaller #0 PREEMPT(full)
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
=====================================================

---
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