Re: [PATCH net] mptcp: never allow the PM to close a listener subflow

[Mat Martineau <mathew.j.martineau@linux.intel.com>]

On Sat, 11 Dec 2021, Paolo Abeni wrote:

> Currently, when deleting an endpoint the netlink PM treverses
> all the local MPTCP sockets, regardless of their status.
>
> If an MPTCP listener socket is bound to the IP matching the
> delete endpoint, the listener TCP socket will be closed.
> That is unexpected, the PM should only affect data subflows.
>
> Additionally, syzbot was able to trigger a NULL ptr dereference
> due to the above:
>
> general protection fault, probably for non-canonical address 0xdffffc0000000003: 0000 [#1] PREEMPT SMP KASAN
> KASAN: null-ptr-deref in range [0x0000000000000018-0x000000000000001f]
> CPU: 1 PID: 6550 Comm: syz-executor122 Not tainted 5.16.0-rc4-syzkaller #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> RIP: 0010:__lock_acquire+0xd7d/0x54a0 kernel/locking/lockdep.c:4897
> Code: 0f 0e 41 be 01 00 00 00 0f 86 c8 00 00 00 89 05 69 cc 0f 0e e9 bd 00 00 00 48 b8 00 00 00 00 00 fc ff df 48 89 da 48 c1 ea 03 <80> 3c 02 00 0f 85 f3 2f 00 00 48 81 3b 20 75 17 8f 0f 84 52 f3 ff
> RSP: 0018:ffffc90001f2f818 EFLAGS: 00010016
> RAX: dffffc0000000000 RBX: 0000000000000018 RCX: 0000000000000000
> RDX: 0000000000000003 RSI: 0000000000000000 RDI: 0000000000000001
> RBP: 0000000000000000 R08: 0000000000000001 R09: 0000000000000001
> R10: 0000000000000000 R11: 000000000000000a R12: 0000000000000000
> R13: ffff88801b98d700 R14: 0000000000000000 R15: 0000000000000001
> FS:  00007f177cd3d700(0000) GS:ffff8880b9d00000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00007f177cd1b268 CR3: 000000001dd55000 CR4: 0000000000350ee0
> Call Trace:
> <TASK>
> lock_acquire kernel/locking/lockdep.c:5637 [inline]
> lock_acquire+0x1ab/0x510 kernel/locking/lockdep.c:5602
> __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
> _raw_spin_lock_irqsave+0x39/0x50 kernel/locking/spinlock.c:162
> finish_wait+0xc0/0x270 kernel/sched/wait.c:400
> inet_csk_wait_for_connect net/ipv4/inet_connection_sock.c:464 [inline]
> inet_csk_accept+0x7de/0x9d0 net/ipv4/inet_connection_sock.c:497
> mptcp_accept+0xe5/0x500 net/mptcp/protocol.c:2865
> inet_accept+0xe4/0x7b0 net/ipv4/af_inet.c:739
> mptcp_stream_accept+0x2e7/0x10e0 net/mptcp/protocol.c:3345
> do_accept+0x382/0x510 net/socket.c:1773
> __sys_accept4_file+0x7e/0xe0 net/socket.c:1816
> __sys_accept4+0xb0/0x100 net/socket.c:1846
> __do_sys_accept net/socket.c:1864 [inline]
> __se_sys_accept net/socket.c:1861 [inline]
> __x64_sys_accept+0x71/0xb0 net/socket.c:1861
> do_syscall_x64 arch/x86/entry/common.c:50 [inline]
> do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
> entry_SYSCALL_64_after_hwframe+0x44/0xae
> RIP: 0033:0x7f177cd8b8e9
> Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 b1 14 00 00 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 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48
> RSP: 002b:00007f177cd3d308 EFLAGS: 00000246 ORIG_RAX: 000000000000002b
> RAX: ffffffffffffffda RBX: 00007f177ce13408 RCX: 00007f177cd8b8e9
> RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000003
> RBP: 00007f177ce13400 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000246 R12: 00007f177ce1340c
> R13: 00007f177cde1004 R14: 6d705f706374706d R15: 0000000000022000
> </TASK>
>
> Fix the issue explicitly skipping MPTCP socket in TCP_LISTEN
> status.
>
> Reported-and-tested-by: syzbot+e4d843bb96a9431e6331@syzkaller.appspotmail.com
> Reviewed-by: Mat Martineau <mathew.j.martineau@linux.intel.com>

Just re-confirming that I'd like to see this merged for the -net branch!

Thanks,

Mat


> Fixes: 740d798e8767 ("mptcp: remove id 0 address")
> Signed-off-by: Paolo Abeni <pabeni@redhat.com>
> ---
> net/mptcp/pm_netlink.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/net/mptcp/pm_netlink.c b/net/mptcp/pm_netlink.c
> index 7b96be1e9f14..f523051f5aef 100644
> --- a/net/mptcp/pm_netlink.c
> +++ b/net/mptcp/pm_netlink.c
> @@ -700,6 +700,9 @@ static void mptcp_pm_nl_rm_addr_or_subflow(struct mptcp_sock *msk,
>
> 	msk_owned_by_me(msk);
>
> +	if (sk->sk_state == TCP_LISTEN)
> +		return;
> +
> 	if (!rm_list->nr)
> 		return;
>
> -- 
> 2.33.1
>
>
>

--
Mat Martineau
Intel