linux-kernel - WARNING: suspicious RCU usage in count

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Message-ID: <0000000000009867cb05b699f5b6@google.com>
Date:   Wed, 16 Dec 2020 11:34:10 -0800
From:   syzbot <syzbot+51ce7a5794c3b12a70d1@...kaller.appspotmail.com>
To:     linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        syzkaller-bugs@...glegroups.com, viro@...iv.linux.org.uk
Subject: WARNING: suspicious RCU usage in count

Hello,

syzbot found the following issue on:

HEAD commit:    7f376f19 Merge tag 'mtd/fixes-for-5.10-rc8' of git://git.k..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1217bb7f500000
kernel config:  https://syzkaller.appspot.com/x/.config?x=ee8a1012a5314210
dashboard link: https://syzkaller.appspot.com/bug?extid=51ce7a5794c3b12a70d1
compiler:       gcc (GCC) 10.1.0-syz 20200507
userspace arch: i386

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+51ce7a5794c3b12a70d1@...kaller.appspotmail.com

=============================
WARNING: suspicious RCU usage
5.10.0-rc7-syzkaller #0 Not tainted
-----------------------------
kernel/sched/core.c:7270 Illegal context switch in RCU-bh read-side critical section!

other info that might help us debug this:


rcu_scheduler_active = 2, debug_locks = 0
no locks held by udevd/9038.

stack backtrace:
CPU: 3 PID: 9038 Comm: udevd Not tainted 5.10.0-rc7-syzkaller #0
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.12.0-59-gc9ba5276e321-prebuilt.qemu.org 04/01/2014
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x107/0x163 lib/dump_stack.c:118
 ___might_sleep+0x220/0x2b0 kernel/sched/core.c:7270
 count.constprop.0+0x164/0x270 fs/exec.c:449
 do_execveat_common+0x2fd/0x7c0 fs/exec.c:1893
 do_execve fs/exec.c:1983 [inline]
 __do_sys_execve fs/exec.c:2059 [inline]
 __se_sys_execve fs/exec.c:2054 [inline]
 __x64_sys_execve+0x8f/0xc0 fs/exec.c:2054
 do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x7fbc6f64c207
Code: 77 19 f4 48 89 d7 44 89 c0 0f 05 48 3d 00 f0 ff ff 76 e0 f7 d8 64 41 89 01 eb d8 f7 d8 64 41 89 01 eb df b8 3b 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 02 f3 c3 48 8b 15 00 8c 2d 00 f7 d8 64 89 02
RSP: 002b:00007ffcfe4966d8 EFLAGS: 00000206
 ORIG_RAX: 000000000000003b
RAX: ffffffffffffffda RBX: 00000000ffffffff RCX: 00007fbc6f64c207
RDX: 0000000000f1dfd0 RSI: 00007ffcfe4967d0 RDI: 00007ffcfe4977e0
RBP: 0000000000625500 R08: 00000000000022fb R09: 00000000000022fb
R10: 0000000000000000 R11: 0000000000000206 R12: 0000000000f1dfd0
R13: 0000000000000007 R14: 0000000000f0e250 R15: 0000000000000005


---
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