[syzbot] [mptcp?] WARNING in subflow_data_ready

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 9c5d00cb7b6b Merge tag 'perf-tools-fixes-for-v6.6-2-2023-1..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=123fbacd680000
kernel config: https://syzkaller.appspot.com/x/.config?x=530f7d8ed0a57417
dashboard link: https://syzkaller.appspot.com/bug?extid=c53d4d3ddb327e80bc51
compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/8423b244df95/disk-9c5d00cb.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/aaee5e776b7e/vmlinux-9c5d00cb.xz
kernel image: https://storage.googleapis.com/syzbot-assets/11fb49db00f3/bzImage-9c5d00cb.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+c53d4d...@syzkaller.appspotmail.com

------------[ cut here ]------------
WARNING: CPU: 1 PID: 18534 at net/mptcp/subflow.c:1405 subflow_data_ready+0x39f/0x4e0 net/mptcp/subflow.c:1405
Modules linked in:
CPU: 1 PID: 18534 Comm: syz-executor.2 Not tainted 6.6.0-rc6-syzkaller-00285-g9c5d00cb7b6b #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/06/2023
RIP: 0010:subflow_data_ready+0x39f/0x4e0 net/mptcp/subflow.c:1405
Code: 18 89 ee e8 a3 80 62 f7 40 84 ed 75 1f e8 69 85 62 f7 44 89 f6 bf 07 00 00 00 e8 cc 80 62 f7 41 83 fe 07 74 07 e8 51 85 62 f7 <0f> 0b e8 4a 85 62 f7 48 89 df e8 02 b2 ff ff 31 ff 89 c5 89 c6 e8
RSP: 0000:ffffc90015aff3a8 EFLAGS: 00010246
RAX: 0000000000000000 RBX: ffff88807c2e9880 RCX: 0000000000000100
RDX: ffff88801f458000 RSI: ffffffff8a25449f RDI: 0000000000000005
RBP: 0000000000000000 R08: 0000000000000005 R09: 0000000000000007
R10: 000000000000000b R11: ffffffff88331ae6 R12: 1ffff92002b5fe75
R13: ffff8880208d0a00 R14: 000000000000000b R15: ffff88802e60af00
FS: 0000555556c8e480(0000) GS:ffff8880b9900000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f7455279b13 CR3: 000000007899e000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
tcp_data_ready+0x14c/0x5b0 net/ipv4/tcp_input.c:5034
tcp_data_queue+0x25fc/0x4f10 net/ipv4/tcp_input.c:5114
tcp_rcv_state_process+0x1871/0x4d00 net/ipv4/tcp_input.c:6728
tcp_v4_do_rcv+0x346/0x9e0 net/ipv4/tcp_ipv4.c:1751
tcp_v4_rcv+0x33a9/0x3b40 net/ipv4/tcp_ipv4.c:2151
ip_protocol_deliver_rcu+0x9f/0x480 net/ipv4/ip_input.c:205
ip_local_deliver_finish+0x2e4/0x510 net/ipv4/ip_input.c:233
NF_HOOK include/linux/netfilter.h:304 [inline]
NF_HOOK include/linux/netfilter.h:298 [inline]
ip_local_deliver+0x1b6/0x550 net/ipv4/ip_input.c:254
dst_input include/net/dst.h:468 [inline]
ip_rcv_finish+0x1c4/0x2e0 net/ipv4/ip_input.c:449
NF_HOOK include/linux/netfilter.h:304 [inline]
NF_HOOK include/linux/netfilter.h:298 [inline]
ip_rcv+0xc9/0x430 net/ipv4/ip_input.c:569
__netif_receive_skb_one_core+0x115/0x180 net/core/dev.c:5552
__netif_receive_skb+0x1f/0x1b0 net/core/dev.c:5666
process_backlog+0x101/0x6b0 net/core/dev.c:5994
__napi_poll.constprop.0+0xb4/0x530 net/core/dev.c:6556
napi_poll net/core/dev.c:6623 [inline]
net_rx_action+0x956/0xe90 net/core/dev.c:6756
__do_softirq+0x218/0x965 kernel/softirq.c:553
invoke_softirq kernel/softirq.c:427 [inline]
__irq_exit_rcu kernel/softirq.c:632 [inline]
irq_exit_rcu+0xb7/0x120 kernel/softirq.c:644
sysvec_apic_timer_interrupt+0x47/0xc0 arch/x86/kernel/apic/apic.c:1074
asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:645
RIP: 0033:0x7f50c2238602
Code: 48 39 d1 72 f3 48 83 e8 08 48 39 f2 73 17 66 2e 0f 1f 84 00 00 00 00 00 48 8b 70 f8 48 83 e8 08 48 39 f2 72 f3 48 39 c3 73 3e <48> 89 33 48 83 c3 08 48 8b 70 f8 48 89 08 48 8b 0b 49 8b 14 24 eb
RSP: 002b:00007f50c24bfa00 EFLAGS: 00000287
RAX: 00007f50c1c009a0 RBX: 00007f50c1c00678 RCX: ffffffff813205d6
RDX: ffffffff813205d6 RSI: ffffffff813205d6 RDI: 00007f50c1c00a50
RBP: 00007f50c1c00570 R08: 00007f50c1c007d8 R09: 0000000000000317
R10: 00000000817374e2 R11: 0000000000000246 R12: 00007f50c1c00568
R13: 0000000000000014 R14: 00007f50c2390000 R15: 00007f50c239c018
</TASK>


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[Paolo Abeni]

On Wed, 2023-10-25 at 11:48 -0700, syzbot wrote:
> syzbot found the following issue on:
>
> HEAD commit: 9c5d00cb7b6b Merge tag 'perf-tools-fixes-for-v6.6-2-2023-1..
> git tree: upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=123fbacd680000
> kernel config: https://syzkaller.appspot.com/x/.config?x=530f7d8ed0a57417
> dashboard link: https://syzkaller.appspot.com/bug?extid=c53d4d3ddb327e80bc51
> compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40

FTR: preemptible kernel, last mptcp program run on the CPU splatting
is:

r0 = socket$inet_mptcp(0x2, 0x1, 0x106)
bind$inet(r0, &(0x7f0000000040)={0x2, 0x4e24, @multicast2}, 0x10)
sendmmsg$inet(r0, &(0x7f0000000440)=[{{&(0x7f00000000c0)={0x2, 0x4e24, @empty}, 0x10, 0x0}}], 0x1, 0x24040890)
r1 = socket$nl_generic(0x10, 0x3, 0x10)
r2 = syz_genetlink_get_family_id$mptcp(&(0x7f0000000080), 0xffffffffffffffff)
setsockopt$inet_tcp_buf(r0, 0x6, 0xd, &(0x7f0000000140)="a7", 0x1)
sendmsg$MPTCP_PM_CMD_ADD_ADDR(r1, &(0x7f0000000300)={0x0, 0x0, &(0x7f0000000100)={&(0x7f0000000000)={0x28, r2, 0x1, 0x0, 0x0, {0x2}, [@MPTCP_PM_ATTR_ADDR={0x14, 0x1, 0x0, 0x1, [@MPTCP_PM_ADDR_ATTR_ADDR4={0x8, 0x3, @multicast2=0x7f000001}, @MPTCP_PM_ADDR_ATTR_FAMILY={0x6, 0x1, 0x2}]}]}, 0x28}, 0x1, 0xf00000000000000}, 0x0)

self-connecting fast-open with an empty data buffer (on a preemptible
kernel, what could possibly go wrong?!? :-P)

The splat is caused by the following check:

WARN_ON_ONCE(!__mptcp_check_fallback(msk) && !subflow->mp_capable &&
!subflow->mp_join && !(state & TCPF_CLOSE));

Without a repro it's hard to guess what is going on, but looks a valid
mptcp related issue.

/P