[moderation] [fs?] KCSAN: data-race in shrink_dentry_list / step_into (7)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 70293240c5ce Merge tag 'timers-urgent-2024-03-23' of git:/..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=178cedc9180000
kernel config: https://syzkaller.appspot.com/x/.config?x=5bd3d8ca9a9838e3
dashboard link: https://syzkaller.appspot.com/bug?extid=fc3368134afd31deb75f
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
CC: [bra...@kernel.org ja...@suse.cz 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/048466107418/disk-70293240.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/6817d7370564/vmlinux-70293240.xz
kernel image: https://storage.googleapis.com/syzbot-assets/16e8b44bfb95/bzImage-70293240.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+fc3368...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in shrink_dentry_list / step_into

read-write to 0xffff8881079ff240 of 4 bytes by task 15786 on cpu 0:
d_shrink_del fs/dcache.c:449 [inline]
shrink_dentry_list+0x226/0x3e0 fs/dcache.c:1067
shrink_dcache_sb+0x165/0x2a0 fs/dcache.c:1195
reconfigure_super+0x3fe/0x5a0 fs/super.c:1049
do_remount fs/namespace.c:2892 [inline]
path_mount+0x96e/0xb30 fs/namespace.c:3671
do_mount fs/namespace.c:3692 [inline]
__do_sys_mount fs/namespace.c:3898 [inline]
__se_sys_mount+0x27f/0x2d0 fs/namespace.c:3875
__x64_sys_mount+0x67/0x80 fs/namespace.c:3875
do_syscall_64+0xd3/0x1d0
entry_SYSCALL_64_after_hwframe+0x6d/0x75

read to 0xffff8881079ff240 of 4 bytes by task 14679 on cpu 1:
__follow_mount_rcu fs/namei.c:1485 [inline]
handle_mounts fs/namei.c:1536 [inline]
step_into+0xe7/0x810 fs/namei.c:1842
open_last_lookups fs/namei.c:3589 [inline]
path_openat+0x10fc/0x1d80 fs/namei.c:3796
do_filp_open+0xf7/0x200 fs/namei.c:3826
do_sys_openat2+0xab/0x120 fs/open.c:1406
do_sys_open fs/open.c:1421 [inline]
__do_sys_openat fs/open.c:1437 [inline]
__se_sys_openat fs/open.c:1432 [inline]
__x64_sys_openat+0xf3/0x120 fs/open.c:1432
do_syscall_64+0xd3/0x1d0
entry_SYSCALL_64_after_hwframe+0x6d/0x75

value changed: 0x00280400 -> 0x00200000

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 14679 Comm: syz-executor.1 Not tainted 6.8.0-syzkaller-13213-g70293240c5ce #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/29/2024
==================================================================


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