[moderation] [kernel?] KCSAN: data-race in pcpu_alloc_noprof / pcpu_balance_workfn

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 44ef20baed8e Merge tag 's390-6.10-4' of git://git.kernel.o..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1143c1de980000
kernel config: https://syzkaller.appspot.com/x/.config?x=68336ea4b6f4fc09
dashboard link: https://syzkaller.appspot.com/bug?extid=433f6493e3caec5344d0
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
CC: [b...@alien8.de dave....@linux.intel.com h...@zytor.com linux-...@vger.kernel.org mi...@redhat.com tg...@linutronix.de x...@kernel.org]

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/17d2a4a1dbe1/disk-44ef20ba.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/c1ea08f344a7/vmlinux-44ef20ba.xz
kernel image: https://storage.googleapis.com/syzbot-assets/43f60f6b9c80/bzImage-44ef20ba.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+433f64...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in pcpu_alloc_noprof / pcpu_balance_workfn

read-write to 0xffffffff8841f6ac of 4 bytes by task 8 on cpu 0:
pcpu_update_empty_pages mm/percpu.c:602 [inline]
pcpu_chunk_populated mm/percpu.c:1531 [inline]
pcpu_balance_populated mm/percpu.c:2062 [inline]
pcpu_balance_workfn+0x94e/0xa60 mm/percpu.c:2212
process_one_work kernel/workqueue.c:3231 [inline]
process_scheduled_works+0x483/0x9a0 kernel/workqueue.c:3312
worker_thread+0x526/0x730 kernel/workqueue.c:3393
kthread+0x1d1/0x210 kernel/kthread.c:389
ret_from_fork+0x4b/0x60 arch/x86/kernel/process.c:147
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

read to 0xffffffff8841f6ac of 4 bytes by task 4363 on cpu 1:
pcpu_alloc_noprof+0x9a7/0x10c0 mm/percpu.c:1894
mm_alloc_cid_noprof include/linux/mm_types.h:1172 [inline]
mm_init+0x47f/0x6f0 kernel/fork.c:1301
dup_mm kernel/fork.c:1685 [inline]
copy_mm+0x11e/0x11d0 kernel/fork.c:1737
copy_process+0xee1/0x1f90 kernel/fork.c:2390
kernel_clone+0x16a/0x570 kernel/fork.c:2797
__do_sys_clone kernel/fork.c:2940 [inline]
__se_sys_clone kernel/fork.c:2924 [inline]
__x64_sys_clone+0xe8/0x120 kernel/fork.c:2924
x64_sys_call+0x23e7/0x2d70 arch/x86/include/generated/asm/syscalls_64.h:57
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xc9/0x1c0 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x00000001 -> 0x00000004

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 4363 Comm: syz-executor.3 Not tainted 6.10.0-rc3-syzkaller-00164-g44ef20baed8e #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/07/2024
==================================================================


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