[moderation] [fs?] KCSAN: data-race in __dentry_kill / step_into (8)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 22a40d14b572 Linux 6.10-rc6
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=15d157fa980000
kernel config: https://syzkaller.appspot.com/x/.config?x=5b9537cd00be479e
dashboard link: https://syzkaller.appspot.com/bug?extid=8cbdf86ac3f842471303
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/ebe2f3933faf/disk-22a40d14.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/7227032da0fe/vmlinux-22a40d14.xz
kernel image: https://storage.googleapis.com/syzbot-assets/a330dc1e107b/bzImage-22a40d14.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+8cbdf8...@syzkaller.appspotmail.com

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

read-write to 0xffff88810642e840 of 4 bytes by task 3065 on cpu 1:
dentry_unlist fs/dcache.c:548 [inline]
__dentry_kill+0x228/0x4b0 fs/dcache.c:617
dput+0x5c/0xd0 fs/dcache.c:845
do_unlinkat+0x257/0x4c0 fs/namei.c:4410
__do_sys_unlink fs/namei.c:4455 [inline]
__se_sys_unlink fs/namei.c:4453 [inline]
__x64_sys_unlink+0x30/0x40 fs/namei.c:4453
x64_sys_call+0x28a3/0x2d70 arch/x86/include/generated/asm/syscalls_64.h:88
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xc9/0x1c0 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff88810642e840 of 4 bytes by task 2784 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+0x169/0x230 fs/namei.c:2010
lookup_last fs/namei.c:2469 [inline]
path_lookupat+0x10a/0x2b0 fs/namei.c:2493
filename_lookup+0x127/0x300 fs/namei.c:2522
user_path_at_empty+0x42/0x120 fs/namei.c:2929
do_readlinkat+0x92/0x210 fs/stat.c:499
__do_sys_readlink fs/stat.c:532 [inline]
__se_sys_readlink fs/stat.c:529 [inline]
__x64_sys_readlink+0x47/0x60 fs/stat.c:529
x64_sys_call+0x264b/0x2d70 arch/x86/include/generated/asm/syscalls_64.h:90
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xc9/0x1c0 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x00600008 -> 0x00008008

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 2784 Comm: udevd Not tainted 6.10.0-rc6-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/07/2024
==================================================================


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