[syzbot] [kernel?] KCSAN: data-race in pcpu_alloc_noprof / pcpu_balance_workfn (2)

[syzbot <syzbot+6d392a44667baa45bb5a@syzkaller.appspotmail.com>]

Hello,

syzbot found the following issue on:

HEAD commit:    d5d547aa7b51 Merge tag 'random-6.11-rc6-for-linus' of git:..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=164c067b980000
kernel config:  https://syzkaller.appspot.com/x/.config?x=6fafac02e339cc84
dashboard link: https://syzkaller.appspot.com/bug?extid=6d392a44667baa45bb5a
compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/e636aa58c364/disk-d5d547aa.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/f5ecd0d96afa/vmlinux-d5d547aa.xz
kernel image: https://storage.googleapis.com/syzbot-assets/fe7d474f148f/bzImage-d5d547aa.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+6d392a44667baa45bb5a@syzkaller.appspotmail.com

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

read-write to 0xffffffff88bb27ac of 4 bytes by task 3354 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+0x526/0x6e0 kernel/workqueue.c:3389
 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 0xffffffff88bb27ac of 4 bytes by task 6821 on cpu 1:
 pcpu_alloc_noprof+0x9a7/0x10c0 mm/percpu.c:1894
 bpf_map_alloc_percpu+0xad/0x210 kernel/bpf/syscall.c:466
 prealloc_init+0x19f/0x470 kernel/bpf/hashtab.c:341
 htab_map_alloc+0x630/0x8e0 kernel/bpf/hashtab.c:576
 map_create+0x83c/0xb90 kernel/bpf/syscall.c:1333
 __sys_bpf+0x667/0x7a0 kernel/bpf/syscall.c:5692
 __do_sys_bpf kernel/bpf/syscall.c:5817 [inline]
 __se_sys_bpf kernel/bpf/syscall.c:5815 [inline]
 __x64_sys_bpf+0x43/0x50 kernel/bpf/syscall.c:5815
 x64_sys_call+0x2625/0x2d60 arch/x86/include/generated/asm/syscalls_64.h:322
 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 UID: 0 PID: 6821 Comm: syz.4.1651 Not tainted 6.11.0-rc5-syzkaller-00081-gd5d547aa7b51 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/06/2024
==================================================================


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