[moderation] [mm?] KCSAN: data-race in copy_mm / lru_gen_del_mm

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: e84d960149e7 Merge tag 'for-6.19-rc5-tag' of git://git.ker..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=11d1b3fc580000
kernel config: https://syzkaller.appspot.com/x/.config?x=676c6f0212d0c041
dashboard link: https://syzkaller.appspot.com/bug?extid=2e51198bb1b40e8ab1cf
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
CC: [ak...@linux-foundation.org axelra...@google.com da...@kernel.org han...@cmpxchg.org linux-...@vger.kernel.org linu...@kvack.org lorenzo...@oracle.com mho...@kernel.org shakee...@linux.dev wei...@google.com yua...@google.com zhengq...@bytedance.com]

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/e2c3723b9ab1/disk-e84d9601.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/5790bc964aa6/vmlinux-e84d9601.xz
kernel image: https://storage.googleapis.com/syzbot-assets/023ce82e3277/bzImage-e84d9601.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+2e5119...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in copy_mm / lru_gen_del_mm

write to 0xffff88810a537238 of 8 bytes by task 7320 on cpu 0:
__list_del include/linux/list.h:203 [inline]
__list_del_entry include/linux/list.h:226 [inline]
list_del_init include/linux/list.h:295 [inline]
lru_gen_del_mm+0x28a/0x3e0 mm/vmscan.c:2953
__mmput+0x17a/0x1c0 kernel/fork.c:1183
mmput+0x40/0x50 kernel/fork.c:1196
exit_mm+0xe3/0x180 kernel/exit.c:581
do_exit+0x3fa/0x1590 kernel/exit.c:959
do_group_exit+0x138/0x140 kernel/exit.c:1112
__do_sys_exit_group kernel/exit.c:1123 [inline]
__se_sys_exit_group kernel/exit.c:1121 [inline]
__x64_sys_exit_group+0x1f/0x20 kernel/exit.c:1121
x64_sys_call+0x2fff/0x3000 arch/x86/include/generated/asm/syscalls_64.h:232
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xc0/0x2a0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff88810a536c00 of 1664 bytes by task 7321 on cpu 1:
dup_mm kernel/fork.c:1523 [inline]
copy_mm+0xe1/0x370 kernel/fork.c:1581
copy_process+0xcbd/0x1f10 kernel/fork.c:2221
kernel_clone+0x16b/0x5b0 kernel/fork.c:2651
__do_sys_clone kernel/fork.c:2792 [inline]
__se_sys_clone kernel/fork.c:2776 [inline]
__x64_sys_clone+0x143/0x180 kernel/fork.c:2776
x64_sys_call+0x12d0/0x3000 arch/x86/include/generated/asm/syscalls_64.h:57
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xc0/0x2a0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 7321 Comm: dhcpcd-run-hook 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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