KCSAN: data-race in __percpu_ref_switch_mode / percpu_ref_switch_to_atomic_rcu (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: f0fddcec6b62 Merge tag 'for-5.14-rc2-tag' of git://git.ker..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=14ac2332300000
kernel config: https://syzkaller.appspot.com/x/.config?x=ce8fa05c1b3f3e8a
dashboard link: https://syzkaller.appspot.com/bug?extid=db891a54585229971137
compiler: Debian clang version 11.0.1-2, GNU ld (GNU Binutils for Debian) 2.35.1
CC: [linux-...@vger.kernel.org mi...@kernel.org pet...@infradead.org valentin....@arm.com]

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

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+db891a...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in __percpu_ref_switch_mode / percpu_ref_switch_to_atomic_rcu

write to 0xffff8881321ba450 of 8 bytes by interrupt on cpu 0:
percpu_ref_call_confirm_rcu lib/percpu-refcount.c:156 [inline]
percpu_ref_switch_to_atomic_rcu+0x188/0x360 lib/percpu-refcount.c:205
rcu_do_batch kernel/rcu/tree.c:2550 [inline]
rcu_core+0xb95/0xd50 kernel/rcu/tree.c:2785
rcu_core_si+0x9/0x10 kernel/rcu/tree.c:2798
__do_softirq+0x12c/0x26e kernel/softirq.c:558
run_ksoftirqd+0x13/0x20 kernel/softirq.c:920
smpboot_thread_fn+0x22f/0x330 kernel/smpboot.c:164
kthread+0x262/0x280 kernel/kthread.c:319
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295

read to 0xffff8881321ba450 of 8 bytes by task 10399 on cpu 1:
__percpu_ref_switch_mode+0xe6/0x3b0 lib/percpu-refcount.c:275
percpu_ref_resurrect+0xc2/0x110 lib/percpu-refcount.c:473
io_refs_resurrect fs/io_uring.c:1116 [inline]
__io_uring_register fs/io_uring.c:10069 [inline]
__do_sys_io_uring_register+0xd27/0x1ea0 fs/io_uring.c:10201
__se_sys_io_uring_register fs/io_uring.c:10181 [inline]
__x64_sys_io_uring_register+0x4f/0x60 fs/io_uring.c:10181
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x3d/0x90 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae

value changed: 0xffffffff818aca90 -> 0x0000000000000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 10399 Comm: syz-executor.1 Not tainted 5.14.0-rc2-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
==================================================================


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[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.