possible deadlock in mptcp_push_pending

From: syzbot
Date: Wed Feb 17 2021 - 12:33:24 EST

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Hello,

syzbot found the following issue on:

HEAD commit: c48f8607 Merge branch 'PTP-for-DSA-tag_ocelot_8021q'
git tree: net-next
console output: https://syzkaller.appspot.com/x/log.txt?x=16525cb0d00000
kernel config: https://syzkaller.appspot.com/x/.config?x=dbc1ca9e55dc1f9f
dashboard link: https://syzkaller.appspot.com/bug?extid=d1b1723faccb7a43f6d1

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+d1b1723faccb7a43f6d1@xxxxxxxxxxxxxxxxxxxxxxxxx

============================================
WARNING: possible recursive locking detected
5.11.0-rc7-syzkaller #0 Not tainted
--------------------------------------------
syz-executor.1/15600 is trying to acquire lock:
ffff888057303220 (sk_lock-AF_INET6){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1598 [inline]
ffff888057303220 (sk_lock-AF_INET6){+.+.}-{0:0}, at: mptcp_push_pending+0x28b/0x650 net/mptcp/protocol.c:1466

but task is already holding lock:
ffff8880285da520 (sk_lock-AF_INET6){+.+.}-{0:0}, at: inet6_sendmsg+0x99/0xe0 net/ipv6/af_inet6.c:638

other info that might help us debug this:
Possible unsafe locking scenario:

CPU0
----
lock(sk_lock-AF_INET6);
lock(sk_lock-AF_INET6);

*** DEADLOCK ***

May be due to missing lock nesting notation

1 lock held by syz-executor.1/15600:
#0: ffff8880285da520 (sk_lock-AF_INET6){+.+.}-{0:0}, at: inet6_sendmsg+0x99/0xe0 net/ipv6/af_inet6.c:638

stack backtrace:
CPU: 1 PID: 15600 Comm: syz-executor.1 Not tainted 5.11.0-rc7-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+0x107/0x163 lib/dump_stack.c:120
print_deadlock_bug kernel/locking/lockdep.c:2761 [inline]
check_deadlock kernel/locking/lockdep.c:2804 [inline]
validate_chain kernel/locking/lockdep.c:3595 [inline]
__lock_acquire.cold+0x114/0x39e kernel/locking/lockdep.c:4832
lock_acquire kernel/locking/lockdep.c:5442 [inline]
lock_acquire+0x1a8/0x720 kernel/locking/lockdep.c:5407
lock_sock_nested+0xc5/0x110 net/core/sock.c:3071
lock_sock include/net/sock.h:1598 [inline]
mptcp_push_pending+0x28b/0x650 net/mptcp/protocol.c:1466
mptcp_sendmsg+0xde4/0x2830 net/mptcp/protocol.c:1685
inet6_sendmsg+0x99/0xe0 net/ipv6/af_inet6.c:638
sock_sendmsg_nosec net/socket.c:652 [inline]
sock_sendmsg+0xcf/0x120 net/socket.c:672
sock_write_iter+0x289/0x3c0 net/socket.c:999
call_write_iter include/linux/fs.h:1901 [inline]
new_sync_write+0x426/0x650 fs/read_write.c:518
vfs_write+0x791/0xa30 fs/read_write.c:605
ksys_write+0x1ee/0x250 fs/read_write.c:658
do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x465d99
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 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 73 01 c3 48 c7 c1 bc ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f0f45e25188 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 000000000056c0b0 RCX: 0000000000465d99
RDX: 0000000020000001 RSI: 0000000020000000 RDI: 0000000000000003
RBP: 00000000004bcf27 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000056c0b0
R13: 00007ffec3fddc7f R14: 00007f0f45e25300 R15: 0000000000022000
general protection fault, probably for non-canonical address 0xdffffc0000000007: 0000 [#1] PREEMPT SMP KASAN
KASAN: null-ptr-deref in range [0x0000000000000038-0x000000000000003f]
CPU: 0 PID: 15600 Comm: syz-executor.1 Not tainted 5.11.0-rc7-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:mptcp_sendmsg_frag+0xa3f/0x1220 net/mptcp/protocol.c:1330
Code: 80 3c 02 00 0f 85 04 07 00 00 48 8b 04 24 48 8b 98 20 07 00 00 48 b8 00 00 00 00 00 fc ff df 48 8d 7b 38 48 89 fa 48 c1 ea 03 <0f> b6 04 02 84 c0 74 08 3c 03 0f 8e d6 04 00 00 48 8d 7d 10 44 8b
RSP: 0018:ffffc900020577e8 EFLAGS: 00010202
RAX: dffffc0000000000 RBX: 0000000000000000 RCX: 0000000000000000
RDX: 0000000000000007 RSI: 0000000000000000 RDI: 0000000000000038
RBP: ffff88802b42e610 R08: 0000000000000001 R09: ffff88802b42e610
R10: ffffed1005685cc4 R11: 0000000000000000 R12: ffff8880285da400
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000204
FS: 00007f0f45e25700(0000) GS:ffff8880b9c00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000055d4b6e570c0 CR3: 000000005c5ae000 CR4: 00000000001506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
mptcp_push_pending+0x2cc/0x650 net/mptcp/protocol.c:1477
mptcp_sendmsg+0xde4/0x2830 net/mptcp/protocol.c:1685
inet6_sendmsg+0x99/0xe0 net/ipv6/af_inet6.c:638
sock_sendmsg_nosec net/socket.c:652 [inline]
sock_sendmsg+0xcf/0x120 net/socket.c:672
sock_write_iter+0x289/0x3c0 net/socket.c:999
call_write_iter include/linux/fs.h:1901 [inline]
new_sync_write+0x426/0x650 fs/read_write.c:518
vfs_write+0x791/0xa30 fs/read_write.c:605
ksys_write+0x1ee/0x250 fs/read_write.c:658
do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x465d99
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 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 73 01 c3 48 c7 c1 bc ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f0f45e25188 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 000000000056c0b0 RCX: 0000000000465d99
RDX: 0000000020000001 RSI: 0000000020000000 RDI: 0000000000000003
RBP: 00000000004bcf27 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000056c0b0
R13: 00007ffec3fddc7f R14: 00007f0f45e25300 R15: 0000000000022000
Modules linked in:
---[ end trace 88e1139d1c953589 ]---
RIP: 0010:mptcp_sendmsg_frag+0xa3f/0x1220 net/mptcp/protocol.c:1330
Code: 80 3c 02 00 0f 85 04 07 00 00 48 8b 04 24 48 8b 98 20 07 00 00 48 b8 00 00 00 00 00 fc ff df 48 8d 7b 38 48 89 fa 48 c1 ea 03 <0f> b6 04 02 84 c0 74 08 3c 03 0f 8e d6 04 00 00 48 8d 7d 10 44 8b
RSP: 0018:ffffc900020577e8 EFLAGS: 00010202
RAX: dffffc0000000000 RBX: 0000000000000000 RCX: 0000000000000000
RDX: 0000000000000007 RSI: 0000000000000000 RDI: 0000000000000038
RBP: ffff88802b42e610 R08: 0000000000000001 R09: ffff88802b42e610
R10: ffffed1005685cc4 R11: 0000000000000000 R12: ffff8880285da400
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000204
FS: 00007f0f45e25700(0000) GS:ffff8880b9c00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f272a496000 CR3: 000000005c5ae000 CR4: 00000000001506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400

---
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Next message: Ahelenia Ziemiańska: "[PATCH 1/4] HID: multitouch: require Finger field to mark Win8 reports as MT"
Previous message: syzbot: "WARNING in dst_release"
Next in thread: Paolo Abeni: "Re: possible deadlock in mptcp_push_pending"
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