WARNING: locking bug in do_ipv6

WARNING: locking bug in do_ipv6_getsockopt
Status: upstream: reported syz repro on 2019/07/02 16:17
Reported-by: syzbot+babfdd7368c72aac3875@syzkaller.appspotmail.com
First crash: 230d, last: 99d

Cause bisection: the bug happens on the oldest tested release
Crash: BUG: held lock freed in pppol2tp_release (log)
Repro: syz .config

Fix bisection: failed (bisect log)

Sample crash report:

WARNING: CPU: 1 PID: 18374 at kernel/locking/lockdep.c:735 arch_local_save_flags arch/x86/include/asm/paravirt.h:762 [inline]
WARNING: CPU: 1 PID: 18374 at kernel/locking/lockdep.c:735 arch_local_save_flags arch/x86/include/asm/paravirt.h:760 [inline]
WARNING: CPU: 1 PID: 18374 at kernel/locking/lockdep.c:735 look_up_lock_class kernel/locking/lockdep.c:726 [inline]
WARNING: CPU: 1 PID: 18374 at kernel/locking/lockdep.c:735 register_lock_class+0xe10/0x1860 kernel/locking/lockdep.c:1079
Kernel panic - not syncing: panic_on_warn set ...
CPU: 1 PID: 18374 Comm: syz-executor.0 Not tainted 5.2.0-rc7 #65
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x172/0x1f0 lib/dump_stack.c:113
 panic+0x2cb/0x744 kernel/panic.c:219
 __warn.cold+0x20/0x4d kernel/panic.c:576
 report_bug+0x263/0x2b0 lib/bug.c:186
 fixup_bug arch/x86/kernel/traps.c:179 [inline]
 fixup_bug arch/x86/kernel/traps.c:174 [inline]
 do_error_trap+0x11b/0x200 arch/x86/kernel/traps.c:272
 do_invalid_op+0x37/0x50 arch/x86/kernel/traps.c:291
 invalid_op+0x14/0x20 arch/x86/entry/entry_64.S:986
RIP: 0010:look_up_lock_class kernel/locking/lockdep.c:735 [inline]
RIP: 0010:register_lock_class+0xe10/0x1860 kernel/locking/lockdep.c:1079
Code: 00 48 89 da 4d 8b 76 c0 48 b8 00 00 00 00 00 fc ff df 48 c1 ea 03 80 3c 02 00 0f 85 23 07 00 00 4c 89 33 e9 e3 f4 ff ff 0f 0b <0f> 0b e9 ea f3 ff ff 44 89 e0 4c 8b 95 50 ff ff ff 83 c0 01 4c 8b
RSP: 0018:ffff88809ea3f678 EFLAGS: 00010087
RAX: dffffc0000000000 RBX: ffff888090b948e0 RCX: 0000000000000000
RDX: 1ffff1101217291f RSI: 0000000000000000 RDI: ffff888090b948f8
RBP: ffff88809ea3f740 R08: 1ffff11013d47ed7 R09: ffffffff8a65ad40
R10: ffffffff8a2e9180 R11: 0000000000000000 R12: ffffffff8a3243a0
R13: 0000000000000000 R14: 0000000000000000 R15: ffffffff88023e60
 __lock_acquire+0x116/0x5490 kernel/locking/lockdep.c:3674
 lock_acquire+0x16f/0x3f0 kernel/locking/lockdep.c:4303
 __raw_spin_lock_bh include/linux/spinlock_api_smp.h:135 [inline]
 _raw_spin_lock_bh+0x33/0x50 kernel/locking/spinlock.c:175
 spin_lock_bh include/linux/spinlock.h:343 [inline]
 lock_sock_nested+0x41/0x120 net/core/sock.c:2913
 lock_sock include/net/sock.h:1522 [inline]
 do_ipv6_getsockopt.isra.0+0x289/0x2590 net/ipv6/ipv6_sockglue.c:1167
 ipv6_getsockopt+0x186/0x280 net/ipv6/ipv6_sockglue.c:1391
 udpv6_getsockopt+0x68/0xa0 net/ipv6/udp.c:1590
 sock_common_getsockopt+0x94/0xd0 net/core/sock.c:3085
 __sys_getsockopt+0x15f/0x240 net/socket.c:2109
 __do_sys_getsockopt net/socket.c:2120 [inline]
 __se_sys_getsockopt net/socket.c:2117 [inline]
 __x64_sys_getsockopt+0xbe/0x150 net/socket.c:2117
 do_syscall_64+0xfd/0x680 arch/x86/entry/common.c:301
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x4597c9
Code: fd b7 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 0f 83 cb b7 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007fb5fd78ac78 EFLAGS: 00000246 ORIG_RAX: 0000000000000037
RAX: ffffffffffffffda RBX: 0000000000000005 RCX: 00000000004597c9
RDX: 0000000000000036 RSI: 0000000000000029 RDI: 0000000000000004
RBP: 000000000075bfc8 R08: 0000000020000080 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007fb5fd78b6d4
R13: 00000000004c0803 R14: 00000000004d2b88 R15: 00000000ffffffff
Kernel Offset: disabled
Rebooting in 86400 seconds..

Crashes (3):
Manager	Time	Kernel	Commit	Syzkaller	Config	Log	Report	Syz repro	Maintainers
ci-upstream-kasan-gce	2019/07/02 13:07	upstream	6fbc7275	cccc4302	.config	log	report	syz	davem@davemloft.net, kuznet@ms2.inr.ac.ru, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, yoshfuji@linux-ipv6.org
ci-upstream-net-kasan-gce	2019/07/02 10:40	net-next	6e32a74a	cccc4302	.config	log	report	syz	davem@davemloft.net, kuznet@ms2.inr.ac.ru, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, yoshfuji@linux-ipv6.org
ci-upstream-net-kasan-gce	2019/07/02 07:34	net-next	6e32a74a	cccc4302	.config	log	report		davem@davemloft.net, kuznet@ms2.inr.ac.ru, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, yoshfuji@linux-ipv6.org