[moderation] [fs?] KCSAN: data-race in __lookup_mnt / __se_sys_pivot_root (4)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 453f5db0619e Merge tag 'trace-v6.7-rc7' of git://git.kerne..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=13ee1dd9e80000
kernel config: https://syzkaller.appspot.com/x/.config?x=4da1e2da456c3a7d
dashboard link: https://syzkaller.appspot.com/bug?extid=25ba88ea0d6efd892d0e
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
CC: [bra...@kernel.org linux-...@vger.kernel.org linux-...@vger.kernel.org vi...@zeniv.linux.org.uk]

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/c9da66f61dd6/disk-453f5db0.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/8e7a5604afa2/vmlinux-453f5db0.xz
kernel image: https://storage.googleapis.com/syzbot-assets/323c3d73a7c1/bzImage-453f5db0.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+25ba88...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in __lookup_mnt / __se_sys_pivot_root

write to 0xffff8881409da650 of 8 bytes by task 7236 on cpu 1:
unhash_mnt fs/namespace.c:905 [inline]
umount_mnt fs/namespace.c:920 [inline]
__do_sys_pivot_root fs/namespace.c:4235 [inline]
__se_sys_pivot_root+0x642/0x1090 fs/namespace.c:4168
__x64_sys_pivot_root+0x31/0x40 fs/namespace.c:4168
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0x44/0x110 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x63/0x6b

read to 0xffff8881409da650 of 8 bytes by task 7239 on cpu 0:
__lookup_mnt+0x83/0xf0 fs/namespace.c:696
__follow_mount_rcu fs/namei.c:1508 [inline]
handle_mounts fs/namei.c:1538 [inline]
step_into+0x430/0x800 fs/namei.c:1840
walk_component+0x164/0x230 fs/namei.c:2008
lookup_last fs/namei.c:2459 [inline]
path_lookupat+0x10a/0x2a0 fs/namei.c:2483
filename_lookup+0x126/0x300 fs/namei.c:2512
user_path_at_empty+0x42/0x110 fs/namei.c:2911
user_path_at include/linux/namei.h:57 [inline]
do_mount fs/namespace.c:3674 [inline]
__do_sys_mount fs/namespace.c:3886 [inline]
__se_sys_mount+0x24b/0x2d0 fs/namespace.c:3863
__x64_sys_mount+0x67/0x80 fs/namespace.c:3863
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0x44/0x110 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x63/0x6b

value changed: 0xffff888144a8fdc0 -> 0xffff888144a8fc80

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 7239 Comm: syz-executor.3 Not tainted 6.7.0-rc7-syzkaller-00049-g453f5db0619e #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/17/2023
==================================================================


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[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.