[moderation] [fs?] KCSAN: data-race in __dentry_kill / fast_dput (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: d8ec19857b09 Merge tag 'net-6.10-rc2' of git://git.kernel...
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=12047ef2980000
kernel config: https://syzkaller.appspot.com/x/.config?x=b639694183430f97
dashboard link: https://syzkaller.appspot.com/bug?extid=dfcb311253a541a4ee29
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/4c525cb10506/disk-d8ec1985.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/5d3c75ffceb2/vmlinux-d8ec1985.xz
kernel image: https://storage.googleapis.com/syzbot-assets/5a992c1884ee/bzImage-d8ec1985.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+dfcb31...@syzkaller.appspotmail.com

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

write to 0xffff88810601e6d0 of 8 bytes by task 3073 on cpu 1:
__d_drop fs/dcache.c:509 [inline]
__dentry_kill+0x13b/0x4b0 fs/dcache.c:601
shrink_kill fs/dcache.c:1048 [inline]
shrink_dentry_list+0x1bc/0x3e0 fs/dcache.c:1075
shrink_dcache_parent+0x43/0x1b0
d_invalidate+0xa6/0x1c0 fs/dcache.c:1592
lookup_fast+0x254/0x2a0 fs/namei.c:1657
walk_component fs/namei.c:2000 [inline]
link_path_walk+0x403/0x810 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:1405
do_sys_open fs/open.c:1420 [inline]
__do_sys_openat fs/open.c:1436 [inline]
__se_sys_openat fs/open.c:1431 [inline]
__x64_sys_openat+0xf3/0x120 fs/open.c:1431
x64_sys_call+0x1057/0x2d70 arch/x86/include/generated/asm/syscalls_64.h:258
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 0xffff88810601e6d0 of 8 bytes by task 3088 on cpu 0:
hlist_bl_unhashed include/linux/list_bl.h:54 [inline]
d_unhashed include/linux/dcache.h:347 [inline]
retain_dentry fs/dcache.c:686 [inline]
fast_dput+0x62/0x2b0 fs/dcache.c:782
dput+0x24/0xd0 fs/dcache.c:839
handle_mounts fs/namei.c:1553 [inline]
step_into+0x21a/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:1405
do_sys_open fs/open.c:1420 [inline]
__do_sys_openat fs/open.c:1436 [inline]
__se_sys_openat fs/open.c:1431 [inline]
__x64_sys_openat+0xf3/0x120 fs/open.c:1431
x64_sys_call+0x1057/0x2d70 arch/x86/include/generated/asm/syscalls_64.h:258
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: 0xffff888237addc60 -> 0x0000000000000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 3088 Comm: udevd Not tainted 6.10.0-rc1-syzkaller-00104-gd8ec19857b09 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/02/2024
==================================================================


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