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

From: syzbot <[email-masked]>
Date: Mon, 05 Apr 2021 08:45:20 -0700

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: [email-masked]

=============================
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

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