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

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 54e82e93ca93 Merge tag 'core_urgent_for_v6.19_rc4' of git:..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=14964f92580000
kernel config: https://syzkaller.appspot.com/x/.config?x=b319ff1b6a2797ca
dashboard link: https://syzkaller.appspot.com/bug?extid=dc4a60eb3b0f9477a856
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
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/85e2aed11694/disk-54e82e93.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/2c81b30e190f/vmlinux-54e82e93.xz
kernel image: https://storage.googleapis.com/syzbot-assets/532557510550/bzImage-54e82e93.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+dc4a60...@syzkaller.appspotmail.com

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

write to 0xffff88811d67e180 of 4 bytes by task 7209 on cpu 0:
d_make_discardable+0x4f/0xa0 fs/dcache.c:936
simple_unlink+0x68/0x80 fs/libfs.c:807
shmem_unlink+0x12d/0x140 mm/shmem.c:3991
shmem_rename2+0x18e/0x310 mm/shmem.c:4072
vfs_rename+0x97f/0xad0 fs/namei.c:5929
do_renameat2+0x383/0x810 fs/namei.c:6047
__do_sys_rename fs/namei.c:6090 [inline]
__se_sys_rename fs/namei.c:6088 [inline]
__x64_sys_rename+0x58/0x70 fs/namei.c:6088
x64_sys_call+0x24e/0x3000 arch/x86/include/generated/asm/syscalls_64.h:83
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xca/0x2b0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff88811d67e180 of 4 bytes by task 6501 on cpu 1:
dentry_unlist fs/dcache.c:640 [inline]
__dentry_kill+0x2aa/0x4b0 fs/dcache.c:684
finish_dput+0x2b/0x200 fs/dcache.c:879
dput+0x52/0x60 fs/dcache.c:928
end_renaming fs/namei.c:4052 [inline]
do_renameat2+0x44a/0x810 fs/namei.c:6049
__do_sys_rename fs/namei.c:6090 [inline]
__se_sys_rename fs/namei.c:6088 [inline]
__x64_sys_rename+0x58/0x70 fs/namei.c:6088
x64_sys_call+0x24e/0x3000 arch/x86/include/generated/asm/syscalls_64.h:83
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xca/0x2b0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x08200080 -> 0x00200180

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 6501 Comm: udevd Tainted: G W syzkaller #0 PREEMPT(voluntary)
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
==================================================================


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