[moderation] [mm?] KCSAN: data-race in __percpu_counter_init_many / copy_mm (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: f83a4f2a4d8c Merge tag 'erofs-for-6.17-rc6-fixes' of git:/..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=109f5b62580000
kernel config: https://syzkaller.appspot.com/x/.config?x=6e0c213d0735f5dd
dashboard link: https://syzkaller.appspot.com/bug?extid=56d2444ea61a650527b7
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
CC: [Liam.H...@oracle.com ak...@linux-foundation.org bse...@google.com da...@redhat.com dietmar....@arm.com juri....@redhat.com ke...@kernel.org linux-...@vger.kernel.org linu...@kvack.org lorenzo...@oracle.com mgo...@suse.de mho...@suse.com mi...@redhat.com pet...@infradead.org ros...@goodmis.org rp...@kernel.org sur...@google.com vba...@suse.cz vincent...@linaro.org vsch...@redhat.com]

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/c6bab01f3fcb/disk-f83a4f2a.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/9838ffd94c42/vmlinux-f83a4f2a.xz
kernel image: https://storage.googleapis.com/syzbot-assets/9a2b10551476/bzImage-f83a4f2a.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+56d244...@syzkaller.appspotmail.com

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

write to 0xffff8881032d6bb0 of 8 bytes by task 17638 on cpu 0:
__list_add include/linux/list.h:153 [inline]
list_add include/linux/list.h:169 [inline]
__percpu_counter_init_many+0x292/0x310 lib/percpu_counter.c:220
mm_init+0x69d/0x7f0 kernel/fork.c:1082
dup_mm kernel/fork.c:1481 [inline]
copy_mm+0x101/0x370 kernel/fork.c:1537
copy_process+0xd08/0x2000 kernel/fork.c:2175
kernel_clone+0x16c/0x5c0 kernel/fork.c:2605
__do_sys_clone kernel/fork.c:2748 [inline]
__se_sys_clone kernel/fork.c:2732 [inline]
__x64_sys_clone+0xe6/0x120 kernel/fork.c:2732
x64_sys_call+0x119c/0x2ff0 arch/x86/include/generated/asm/syscalls_64.h:57
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xd2/0x200 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff8881032d6780 of 1408 bytes by task 22981 on cpu 1:
dup_mm kernel/fork.c:1479 [inline]
copy_mm+0xe2/0x370 kernel/fork.c:1537
copy_process+0xd08/0x2000 kernel/fork.c:2175
kernel_clone+0x16c/0x5c0 kernel/fork.c:2605
__do_sys_clone kernel/fork.c:2748 [inline]
__se_sys_clone kernel/fork.c:2732 [inline]
__x64_sys_clone+0xe6/0x120 kernel/fork.c:2732
x64_sys_call+0x119c/0x2ff0 arch/x86/include/generated/asm/syscalls_64.h:57
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xd2/0x200 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: 22981 Comm: syz.7.7398 Tainted: G W syzkaller #0 PREEMPT(voluntary)
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025
==================================================================


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