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

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 8f6a15f095a6 Merge tag 'cocci-for-6.10' of git://git.kerne..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=139b2cb2980000
kernel config: https://syzkaller.appspot.com/x/.config?x=25568d6dd96137e2
dashboard link: https://syzkaller.appspot.com/bug?extid=9fd7f6da7918e432f1cd
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/0c2e16313112/disk-8f6a15f0.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/9316e832b078/vmlinux-8f6a15f0.xz
kernel image: https://storage.googleapis.com/syzbot-assets/34b38f4a29b1/bzImage-8f6a15f0.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+9fd7f6...@syzkaller.appspotmail.com

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

read-write to 0xffff888105619f00 of 4 bytes by task 23257 on cpu 1:
dentry_unlist fs/dcache.c:548 [inline]
__dentry_kill+0x228/0x4b0 fs/dcache.c:617
shrink_kill fs/dcache.c:1048 [inline]
shrink_dentry_list+0x1bc/0x3e0 fs/dcache.c:1075
shrink_dcache_sb+0x165/0x2a0 fs/dcache.c:1195
reconfigure_super+0x3fe/0x5a0 fs/super.c:1050
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
x64_sys_call+0x2591/0x2d30 arch/x86/include/generated/asm/syscalls_64.h:166
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xcd/0x1d0 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff888105619f00 of 4 bytes by task 23258 on cpu 0:
__follow_mount_rcu fs/namei.c:1485 [inline]
handle_mounts fs/namei.c:1536 [inline]
step_into+0xe7/0x810 fs/namei.c:1842
walk_component fs/namei.c:2010 [inline]
link_path_walk+0x49d/0x810 fs/namei.c:2331
path_openat+0x1a1/0x1da0 fs/namei.c:3803
do_filp_open+0xf7/0x200 fs/namei.c:3834
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
x64_sys_call+0x2cad/0x2d30 arch/x86/include/generated/asm/syscalls_64.h:258
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xcd/0x1d0 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x00600040 -> 0x00008040

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 23258 Comm: modprobe Tainted: G W 6.9.0-syzkaller-10323-g8f6a15f095a6 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/02/2024
==================================================================


---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzk...@googlegroups.com.

syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.

If the report is already addressed, let syzbot know by replying with:
#syz fix: exact-commit-title

If you want to overwrite report's subsystems, reply with:
#syz set subsystems: new-subsystem
(See the list of subsystem names on the web dashboard)

If the report is a duplicate of another one, reply with:
#syz dup: exact-subject-of-another-report

If you want to undo deduplication, reply with:
#syz undup