[moderation] [fs?] KCSAN: data-race in __dentry_kill / dont_mount

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: a8662bcd2ff1 Merge tag 'v6.15-p3' of git://git.kernel.org/..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=12654be4580000
kernel config: https://syzkaller.appspot.com/x/.config?x=feee5c3d8a6f5d3c
dashboard link: https://syzkaller.appspot.com/bug?extid=555f6ed4f4a85eb963b3
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/b85c4cb3c238/disk-a8662bcd.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/77328acab5c7/vmlinux-a8662bcd.xz
kernel image: https://storage.googleapis.com/syzbot-assets/5988de53c201/bzImage-a8662bcd.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+555f6e...@syzkaller.appspotmail.com

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

read-write to 0xffff88810654cd80 of 4 bytes by task 707 on cpu 0:
dont_mount+0x2a/0x40 include/linux/dcache.h:381
vfs_unlink+0x298/0x430 fs/namei.c:4546
do_unlinkat+0x21b/0x4b0 fs/namei.c:4608
__do_sys_unlink fs/namei.c:4654 [inline]
__se_sys_unlink fs/namei.c:4652 [inline]
__x64_sys_unlink+0x2e/0x40 fs/namei.c:4652
x64_sys_call+0x2358/0x2e10 arch/x86/include/generated/asm/syscalls_64.h:88
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xc9/0x1c0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff88810654cd80 of 4 bytes by task 3003 on cpu 1:
dentry_unlist fs/dcache.c:630 [inline]
__dentry_kill+0x2af/0x4c0 fs/dcache.c:674
dput+0x5c/0xd0 fs/dcache.c:902
handle_mounts fs/namei.c:1640 [inline]
step_into+0x226/0x860 fs/namei.c:1966
walk_component+0x178/0x240 fs/namei.c:2134
lookup_last fs/namei.c:2626 [inline]
path_lookupat+0x103/0x2a0 fs/namei.c:2650
filename_lookup+0x14b/0x340 fs/namei.c:2679
do_readlinkat+0x8b/0x210 fs/stat.c:564
__do_sys_readlink fs/stat.c:601 [inline]
__se_sys_readlink fs/stat.c:598 [inline]
__x64_sys_readlink+0x47/0x60 fs/stat.c:598
x64_sys_call+0x2a81/0x2e10 arch/x86/include/generated/asm/syscalls_64.h:90
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xc9/0x1c0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x00300008 -> 0x00000008

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 3003 Comm: udevd Not tainted 6.14.0-syzkaller-13423-ga8662bcd2ff1 #0 PREEMPT(voluntary)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
==================================================================


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[syzbot]

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