[moderation] [fs?] KCSAN: data-race in __d_instantiate / lookup_fast (9)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 9d89551994a4 Linux 6.13-rc6
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=12adb9c4580000
kernel config: https://syzkaller.appspot.com/x/.config?x=9ab3e6c069ff12aa
dashboard link: https://syzkaller.appspot.com/bug?extid=b472ff7ba000507bd292
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/1a1b97780d86/disk-9d895519.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/923ea83988f7/vmlinux-9d895519.xz
kernel image: https://storage.googleapis.com/syzbot-assets/d5a0eedb3036/bzImage-9d895519.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+b472ff...@syzkaller.appspotmail.com

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

read-write to 0xffff888105714780 of 4 bytes by task 3441 on cpu 0:
__d_instantiate+0x2d5/0x3c0 fs/dcache.c:1879
d_instantiate+0x59/0x80 fs/dcache.c:1904
shmem_symlink+0x36a/0x3a0 mm/shmem.c:3966
vfs_symlink+0xca/0x1d0 fs/namei.c:4669
do_symlinkat+0xdf/0x350 fs/namei.c:4695
__do_sys_symlink fs/namei.c:4716 [inline]
__se_sys_symlink fs/namei.c:4714 [inline]
__x64_sys_symlink+0x50/0x60 fs/namei.c:4714
x64_sys_call+0x28b0/0x2dc0 arch/x86/include/generated/asm/syscalls_64.h:89
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 0xffff888105714780 of 4 bytes by task 3288 on cpu 1:
d_revalidate fs/namei.c:926 [inline]
lookup_fast+0xd9/0x2a0 fs/namei.c:1740
walk_component+0x3f/0x230 fs/namei.c:2108
lookup_last fs/namei.c:2610 [inline]
path_lookupat+0x10a/0x2b0 fs/namei.c:2634
filename_lookup+0x150/0x340 fs/namei.c:2663
vfs_statx+0x9a/0x170 fs/stat.c:344
vfs_fstatat fs/stat.c:366 [inline]
__do_sys_newfstatat fs/stat.c:530 [inline]
__se_sys_newfstatat+0xdc/0x300 fs/stat.c:524
__x64_sys_newfstatat+0x55/0x70 fs/stat.c:524
x64_sys_call+0x236d/0x2dc0 arch/x86/include/generated/asm/syscalls_64.h:263
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: 0x00000008 -> 0x00600008

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 3288 Comm: udevd Tainted: G W 6.13.0-rc6-syzkaller #0
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
==================================================================


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[syzbot]

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