[moderation] [fs?] KCSAN: data-race in __d_instantiate / dput (6)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 55cb5f43689d Merge tag 'trace-v6.7-rc6' of git://git.kerne..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=147fe811e80000
kernel config: https://syzkaller.appspot.com/x/.config?x=989a728d0f884055
dashboard link: https://syzkaller.appspot.com/bug?extid=8b7c4a2d95cf3c32136b
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
CC: [bra...@kernel.org 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/48e180dd5134/disk-55cb5f43.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/8d5228b1803d/vmlinux-55cb5f43.xz
kernel image: https://storage.googleapis.com/syzbot-assets/fc03913fb908/bzImage-55cb5f43.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+8b7c4a...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in __d_instantiate / dput

read-write to 0xffff8881077e2480 of 4 bytes by task 19780 on cpu 0:
__d_instantiate+0x2cd/0x3b0 fs/dcache.c:2010
d_instantiate+0x59/0x80 fs/dcache.c:2035
shmem_symlink+0x364/0x390 mm/shmem.c:3519
vfs_symlink+0xc2/0x1a0 fs/namei.c:4464
do_symlinkat+0xe3/0x340 fs/namei.c:4490
__do_sys_symlink fs/namei.c:4511 [inline]
__se_sys_symlink fs/namei.c:4509 [inline]
__x64_sys_symlink+0x56/0x60 fs/namei.c:4509
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0x44/0x110 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x63/0x6b

read to 0xffff8881077e2480 of 4 bytes by task 2780 on cpu 1:
fast_dput fs/dcache.c:774 [inline]
dput+0x35/0x1f0 fs/dcache.c:900
handle_mounts fs/namei.c:1555 [inline]
step_into+0x21a/0x800 fs/namei.c:1840
walk_component+0x164/0x230 fs/namei.c:2008
lookup_last fs/namei.c:2459 [inline]
path_lookupat+0x10a/0x2a0 fs/namei.c:2483
filename_lookup+0x126/0x300 fs/namei.c:2512
user_path_at_empty+0x42/0x110 fs/namei.c:2911
do_readlinkat+0x92/0x210 fs/stat.c:494
__do_sys_readlink fs/stat.c:527 [inline]
__se_sys_readlink fs/stat.c:524 [inline]
__x64_sys_readlink+0x47/0x50 fs/stat.c:524
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0x44/0x110 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x63/0x6b

value changed: 0x00000008 -> 0x00600008

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 2780 Comm: udevd Not tainted 6.7.0-rc6-syzkaller-00022-g55cb5f43689d #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/17/2023
==================================================================


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[syzbot]

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