[moderation] [fs?] KCSAN: data-race in d_make_discardable / dentry_kill

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: a142da0b2d32 Merge tag 'block-7.2-20260625' of git://git.k..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=13cee6de580000
kernel config: https://syzkaller.appspot.com/x/.config?x=84b3039e8461eef5
dashboard link: https://syzkaller.appspot.com/bug?extid=d1d6dc20ca5d8eb0943c
compiler: Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8
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/55c821bde946/disk-a142da0b.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/778808d12d2a/vmlinux-a142da0b.xz
kernel image: https://storage.googleapis.com/syzbot-assets/9ab191ae8905/bzImage-a142da0b.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+d1d6dc...@syzkaller.appspotmail.com

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

write to 0xffff888105cdeb40 of 4 bytes by task 8881 on cpu 1:
d_make_discardable+0x4f/0x90 fs/dcache.c:1050
simple_unlink+0x68/0x80 fs/libfs.c:808
shmem_unlink+0x12d/0x140 mm/shmem.c:3917
vfs_unlink+0x1c3/0x490 fs/namei.c:5511
filename_unlinkat+0x1dc/0x410 fs/namei.c:5581
__do_sys_unlink fs/namei.c:5616 [inline]
__se_sys_unlink+0x2b/0xe0 fs/namei.c:5613
__x64_sys_unlink+0x1f/0x30 fs/namei.c:5613
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+0x136/0x3c0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff888105cdeb40 of 4 bytes by task 9727 on cpu 0:
dentry_unlist fs/dcache.c:694 [inline]
dentry_kill+0x2d3/0x500 fs/dcache.c:840
finish_dput+0x16/0x1d0 fs/dcache.c:1001
dput+0x48/0x50 fs/dcache.c:1042
end_dirop fs/namei.c:2956 [inline]
filename_unlinkat+0x217/0x410 fs/namei.c:5584
__do_sys_unlink fs/namei.c:5616 [inline]
__se_sys_unlink+0x2b/0xe0 fs/namei.c:5613
__x64_sys_unlink+0x1f/0x30 fs/namei.c:5613
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+0x136/0x3c0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x08300080 -> 0x00000080

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 9727 Comm: udevd Tainted: G W syzkaller #0 PREEMPT(lazy)
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
==================================================================


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