[moderation] [fs?] upstream test error: KCSAN: data-race in d_make_discardable / path_lookupat

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: ec8957276674 Merge tag 'hwmon-for-v7.1-rc3' of git://git.k..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=12d643ce580000
kernel config: https://syzkaller.appspot.com/x/.config?x=2e40c0f41e01837e
dashboard link: https://syzkaller.appspot.com/bug?extid=2cd4ae3e5044e22fe912
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
CC: [bra...@kernel.org ja...@suse.cz linux-...@vger.kernel.org linux-...@vger.kernel.org vi...@zeniv.linux.org.uk]

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/3a76197ce11a/disk-ec895727.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/caee727e7b63/vmlinux-ec895727.xz
kernel image: https://storage.googleapis.com/syzbot-assets/5c20f654441e/bzImage-ec895727.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+2cd4ae...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in d_make_discardable / path_lookupat

write to 0xffff8881007cc780 of 4 bytes by task 3293 on cpu 0:
d_make_discardable+0x4f/0xa0 fs/dcache.c:984
simple_unlink+0x68/0x80 fs/libfs.c:808
shmem_unlink+0x12d/0x140 mm/shmem.c:3981
vfs_unlink+0x1c7/0x490 fs/namei.c:5498
filename_unlinkat+0x1e2/0x410 fs/namei.c:5568
__do_sys_unlink fs/namei.c:5603 [inline]
__se_sys_unlink+0x2b/0xe0 fs/namei.c:5600
__x64_sys_unlink+0x1f/0x30 fs/namei.c:5600
x64_sys_call+0x2eb6/0x3020 arch/x86/include/generated/asm/syscalls_64.h:88
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x12c/0x3b0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff8881007cc780 of 4 bytes by task 2983 on cpu 1:
d_managed include/linux/dcache.h:416 [inline]
step_into fs/namei.c:2135 [inline]
walk_component fs/namei.c:2284 [inline]
lookup_last fs/namei.c:2785 [inline]
path_lookupat+0x1d8/0x500 fs/namei.c:2809
filename_lookup+0x190/0x390 fs/namei.c:2838
do_readlinkat+0x74/0x2f0 fs/stat.c:571
__do_sys_readlink fs/stat.c:605 [inline]
__se_sys_readlink fs/stat.c:602 [inline]
__x64_sys_readlink+0x47/0x60 fs/stat.c:602
x64_sys_call+0x2b51/0x3020 arch/x86/include/generated/asm/syscalls_64.h:90
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x12c/0x3b0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x08300080 -> 0x00004080

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 2983 Comm: udevd Not tainted syzkaller #0 PREEMPT(full)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
==================================================================


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