CVE-2022-50070

In the Linux kernel, the following vulnerability has been resolved:

mptcp: do not queue data on closed subflows

Dipanjan reported a syzbot splat at close time:

WARNING: CPU: 1 PID: 10818 at net/ipv4/af_inet.c:153

inet_sock_destruct+0x6d0/0x8e0 net/ipv4/af_inet.c:153

Modules linked in: uio_ivshmem(OE) uio(E)

CPU: 1 PID: 10818 Comm: kworker/1:16 Tainted: G OE

5.19.0-rc6-g2eae0556bb9d #2

Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS

1.13.0-1ubuntu1.1 04/01/2014

Workqueue: events mptcp_worker

RIP: 0010:inet_sock_destruct+0x6d0/0x8e0 net/ipv4/af_inet.c:153

Code: 21 02 00 00 41 8b 9c 24 28 02 00 00 e9 07 ff ff ff e8 34 4d 91

f9 89 ee 4c 89 e7 e8 4a 47 60 ff e9 a6 fc ff ff e8 20 4d 91 f9 <0f> 0b

e9 84 fe ff ff e8 14 4d 91 f9 0f 0b e9 d4 fd ff ff e8 08 4d

RSP: 0018:ffffc9001b35fa78 EFLAGS: 00010246

RAX: 0000000000000000 RBX: 00000000002879d0 RCX: ffff8881326f3b00

RDX: 0000000000000000 RSI: ffff8881326f3b00 RDI: 0000000000000002

RBP: ffff888179662674 R08: ffffffff87e983a0 R09: 0000000000000000

R10: 0000000000000005 R11: 00000000000004ea R12: ffff888179662400

R13: ffff888179662428 R14: 0000000000000001 R15: ffff88817e38e258

FS: 0000000000000000(0000) GS:ffff8881f5f00000(0000) knlGS:0000000000000000

CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033

CR2: 0000000020007bc0 CR3: 0000000179592000 CR4: 0000000000150ee0

Call Trace:

<TASK>

__sk_destruct+0x4f/0x8e0 net/core/sock.c:2067

sk_destruct+0xbd/0xe0 net/core/sock.c:2112

__sk_free+0xef/0x3d0 net/core/sock.c:2123

sk_free+0x78/0xa0 net/core/sock.c:2134

sock_put include/net/sock.h:1927 [inline]

__mptcp_close_ssk+0x50f/0x780 net/mptcp/protocol.c:2351

__mptcp_destroy_sock+0x332/0x760 net/mptcp/protocol.c:2828

mptcp_worker+0x5d2/0xc90 net/mptcp/protocol.c:2586

process_one_work+0x9cc/0x1650 kernel/workqueue.c:2289

worker_thread+0x623/0x1070 kernel/workqueue.c:2436

kthread+0x2e9/0x3a0 kernel/kthread.c:376

ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:302

</TASK>

The root cause of the problem is that an mptcp-level (re)transmit can

race with mptcp_close() and the packet scheduler checks the subflow

state before acquiring the socket lock: we can try to (re)transmit on

an already closed ssk.

Fix the issue checking again the subflow socket status under the

subflow socket lock protection. Additionally add the missing check

for the fallback-to-tcp case.