Re: [syzbot] WARNING: suspicious RCU usage in lock_sock_nested

From: Dmitry Vyukov <dvyukov@google.com>
To: syzbot <syzbot+80a4f8091f8d5ba51de9@syzkaller.appspotmail.com>
Cc: andrii@kernel.org, Alexei Starovoitov <ast@kernel.org>,
	bpf <bpf@vger.kernel.org>, Daniel Borkmann <daniel@iogearbox.net>,
	David Miller <davem@davemloft.net>,
	dsahern@kernel.org, John Fastabend <john.fastabend@gmail.com>,
	Martin KaFai Lau <kafai@fb.com>,
	kpsingh@kernel.org, Jakub Kicinski <kuba@kernel.org>,
	LKML <linux-kernel@vger.kernel.org>,
	netdev <netdev@vger.kernel.org>, Song Liu <songliubraving@fb.com>,
	syzkaller-bugs <syzkaller-bugs@googlegroups.com>,
	Yonghong Song <yhs@fb.com>,
	Hideaki YOSHIFUJI <yoshfuji@linux-ipv6.org>
Subject: Re: [syzbot] WARNING: suspicious RCU usage in lock_sock_nested
Date: Tue, 13 Apr 2021 20:10:39 +0200	[thread overview]
Message-ID: <CACT4Y+asWh+a9snv-V=a=h1i9A-4hWW4fb4=1vnEKH7vgoh-Lw@mail.gmail.com> (raw)
In-Reply-To: <000000000000ce66e005bf3b9531@google.com>

On Mon, Apr 5, 2021 at 5:45 PM syzbot
<syzbot+80a4f8091f8d5ba51de9@syzkaller.appspotmail.com> wrote:
>
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit:    d19cc4bf Merge tag 'trace-v5.12-rc5' of git://git.kernel.o..
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=14898326d00000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=d1a3d65a48dbd1bc
> dashboard link: https://syzkaller.appspot.com/bug?extid=80a4f8091f8d5ba51de9
>
> 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+80a4f8091f8d5ba51de9@syzkaller.appspotmail.com

#syz dup: WARNING: suspicious RCU usage in getname_flags

> =============================
> WARNING: suspicious RCU usage
> 5.12.0-rc5-syzkaller #0 Not tainted
> -----------------------------
> kernel/sched/core.c:8294 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 syz-executor.3/8407.
>
> stack backtrace:
> CPU: 0 PID: 8407 Comm: syz-executor.3 Not tainted 5.12.0-rc5-syzkaller #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> Call Trace:
>  __dump_stack lib/dump_stack.c:79 [inline]
>  dump_stack+0x141/0x1d7 lib/dump_stack.c:120
>  ___might_sleep+0x229/0x2c0 kernel/sched/core.c:8294
>  lock_sock_nested+0x25/0x120 net/core/sock.c:3062
>  lock_sock include/net/sock.h:1600 [inline]
>  do_ip_getsockopt+0x227/0x18e0 net/ipv4/ip_sockglue.c:1536
>  ip_getsockopt+0x84/0x1c0 net/ipv4/ip_sockglue.c:1761
>  tcp_getsockopt+0x86/0xd0 net/ipv4/tcp.c:4239
>  __sys_getsockopt+0x21f/0x5f0 net/socket.c:2161
>  __do_sys_getsockopt net/socket.c:2176 [inline]
>  __se_sys_getsockopt net/socket.c:2173 [inline]
>  __x64_sys_getsockopt+0xba/0x150 net/socket.c:2173
>  do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
>  entry_SYSCALL_64_after_hwframe+0x44/0xae
> RIP: 0033:0x467a6a
> Code: 48 c7 c1 bc ff ff ff f7 d8 64 89 01 48 83 c8 ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 49 89 ca b8 37 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 bc ff ff ff f7 d8 64 89 01 48
> RSP: 002b:00007ffc76a6a848 EFLAGS: 00000246 ORIG_RAX: 0000000000000037
> RAX: ffffffffffffffda RBX: 00007ffc76a6a85c RCX: 0000000000467a6a
> RDX: 0000000000000060 RSI: 0000000000000000 RDI: 0000000000000003
> RBP: 0000000000000003 R08: 00007ffc76a6a85c R09: 00007ffc76a6a8c0
> R10: 00007ffc76a6a860 R11: 0000000000000246 R12: 00007ffc76a6a860
> R13: 000000000005ecdc R14: 0000000000000000 R15: 00007ffc76a6afd0
>
>
> ---
> This report is generated by a bot. It may contain errors.
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>
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