[moderation] [fs?] KCSAN: data-race in __se_sys_pivot_root / choose_mountpoint_rcu

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: f97e18a3f2fb Merge tag 'gpio-updates-for-v6.6' of git://gi..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=11487457a80000
kernel config: https://syzkaller.appspot.com/x/.config?x=fe440f256d065d3b
dashboard link: https://syzkaller.appspot.com/bug?extid=1719f0057f0dcdd8d683
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/b1781aaff038/disk-f97e18a3.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/5b915468fd6d/vmlinux-f97e18a3.xz
kernel image: https://storage.googleapis.com/syzbot-assets/abc8ece931f3/bzImage-f97e18a3.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+1719f0...@syzkaller.appspotmail.com

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

write to 0xffff888130bc2150 of 8 bytes by task 1649 on cpu 0:
unhash_mnt fs/namespace.c:903 [inline]
umount_mnt fs/namespace.c:918 [inline]
__do_sys_pivot_root fs/namespace.c:4233 [inline]
__se_sys_pivot_root+0x642/0x1090 fs/namespace.c:4166
__x64_sys_pivot_root+0x31/0x40 fs/namespace.c:4166
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd

read to 0xffff888130bc2150 of 8 bytes by task 1648 on cpu 1:
mnt_has_parent fs/mount.h:91 [inline]
choose_mountpoint_rcu+0x2b/0x130 fs/namei.c:1299
follow_dotdot_rcu fs/namei.c:1883 [inline]
handle_dots+0x543/0x750 fs/namei.c:1958
walk_component fs/namei.c:1995 [inline]
link_path_walk+0x5e3/0x7e0 fs/namei.c:2328
path_lookupat+0x72/0x2a0 fs/namei.c:2481
filename_lookup+0x126/0x300 fs/namei.c:2511
user_path_at_empty+0x42/0x110 fs/namei.c:2910
user_path_at include/linux/namei.h:57 [inline]
do_mount fs/namespace.c:3672 [inline]
__do_sys_mount fs/namespace.c:3884 [inline]
__se_sys_mount+0x24b/0x2d0 fs/namespace.c:3861
__x64_sys_mount+0x67/0x80 fs/namespace.c:3861
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd

value changed: 0xffff888130bc2000 -> 0xffff88812fd1eb40

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 1648 Comm: syz-executor.1 Tainted: G W 6.5.0-syzkaller-01810-gf97e18a3f2fb #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/26/2023
==================================================================


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[syzbot]

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