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Date:   Sun, 12 Jun 2022 17:16:20 -0700
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Subject: Re: [syzbot] WARNING in exit_tasks_rcu_finish
From:   syzbot <syzbot+9bb26e7c5e8e4fa7e641@syzkaller.appspotmail.com>
To:     brauner@kernel.org, ebiederm@xmission.com, keescook@chromium.org,
        linux-kernel@vger.kernel.org, paulmck@kernel.org,
        syzkaller-bugs@googlegroups.com
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syzbot has found a reproducer for the following issue on:

HEAD commit:    6d0c80680317 Add linux-next specific files for 20220610
git tree:       linux-next
console+strace: https://syzkaller.appspot.com/x/log.txt?x=106611bff00000
kernel config:  https://syzkaller.appspot.com/x/.config?x=a30d6e3e814e5931
dashboard link: https://syzkaller.appspot.com/bug?extid=9bb26e7c5e8e4fa7e641
compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=177b6230080000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=148207bff00000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+9bb26e7c5e8e4fa7e641@syzkaller.appspotmail.com

------------[ cut here ]------------
WARNING: CPU: 1 PID: 4198 at kernel/rcu/tasks.h:1664 exit_tasks_rcu_finish_trace kernel/rcu/tasks.h:1664 [inline]
WARNING: CPU: 1 PID: 4198 at kernel/rcu/tasks.h:1664 exit_tasks_rcu_finish+0x122/0x1b0 kernel/rcu/tasks.h:1006
Modules linked in:
CPU: 1 PID: 4198 Comm: syz-executor403 Not tainted 5.19.0-rc1-next-20220610-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:exit_tasks_rcu_finish_trace kernel/rcu/tasks.h:1664 [inline]
RIP: 0010:exit_tasks_rcu_finish+0x122/0x1b0 kernel/rcu/tasks.h:1006
Code: fc ff df 48 89 fa 48 c1 ea 03 0f b6 04 02 48 89 fa 83 e2 07 38 d0 7f 04 84 c0 75 62 0f b6 85 89 04 00 00 83 e0 01 08 d8 74 0e <0f> 0b 5b 48 89 ef 5d 41 5c e9 00 d2 ff ff 48 b8 00 00 00 00 00 fc
RSP: 0018:ffffc90003a2fb58 EFLAGS: 00010202
RAX: 0000000000000001 RBX: 0000000000000201 RCX: 1ffff1100ebf1091
RDX: 0000000000000001 RSI: 0000000000000000 RDI: ffff888075f88489
RBP: ffff888075f88000 R08: 0000000000000005 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000001 R12: ffff888075f88480
R13: dffffc0000000000 R14: ffff888075f88000 R15: ffffc90003a2fbe8
FS:  0000000000000000(0000) GS:ffff8880b9b00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000555556d916d0 CR3: 000000000ba8e000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 do_exit+0x18f2/0x2a00 kernel/exit.c:844
 do_group_exit+0xd2/0x2f0 kernel/exit.c:925
 get_signal+0x2542/0x2600 kernel/signal.c:2857
 arch_do_signal_or_restart+0x82/0x2300 arch/x86/kernel/signal.c:869
 exit_to_user_mode_loop kernel/entry/common.c:166 [inline]
 exit_to_user_mode_prepare+0x15f/0x250 kernel/entry/common.c:201
 __syscall_exit_to_user_mode_work kernel/entry/common.c:283 [inline]
 syscall_exit_to_user_mode+0x19/0x50 kernel/entry/common.c:294
 do_syscall_64+0x42/0xb0 arch/x86/entry/common.c:86
 entry_SYSCALL_64_after_hwframe+0x46/0xb0
RIP: 0033:0x7fb21689cc79
Code: Unable to access opcode bytes at RIP 0x7fb21689cc4f.
RSP: 002b:00007fb21684d218 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
RAX: fffffffffffffe00 RBX: 00007fb216924408 RCX: 00007fb21689cc79
RDX: 0000000000000000 RSI: 0000000000000080 RDI: 00007fb216924408
RBP: 00007fb216924400 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007fb21692440c
R13: 00007ffe134b471f R14: 00007fb21684d300 R15: 0000000000022000
 </TASK>