[PATCH net] net: Return error from sk_stream_wait_connect() if sk_wait_event() fails

Shigeru Yoshida
2023-12-14T05:15:07Z

The following NULL pointer dereference issue occurred:

BUG: kernel NULL pointer dereference, address: 0000000000000000
<...>
RIP: 0010:ccid_hc_tx_send_packet net/dccp/ccid.h:166 [inline]
RIP: 0010:dccp_write_xmit+0x49/0x140 net/dccp/output.c:356
<...>
Call Trace:
<TASK>
dccp_sendmsg+0x642/0x7e0 net/dccp/proto.c:801
inet_sendmsg+0x63/0x90 net/ipv4/af_inet.c:846
sock_sendmsg_nosec net/socket.c:730 [inline]
__sock_sendmsg+0x83/0xe0 net/socket.c:745
____sys_sendmsg+0x443/0x510 net/socket.c:2558
___sys_sendmsg+0xe5/0x150 net/socket.c:2612
__sys_sendmsg+0xa6/0x120 net/socket.c:2641
__do_sys_sendmsg net/socket.c:2650 [inline]
__se_sys_sendmsg net/socket.c:2648 [inline]
__x64_sys_sendmsg+0x45/0x50 net/socket.c:2648
do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x43/0x110 arch/x86/entry/common.c:82
entry_SYSCALL_64_after_hwframe+0x63/0x6b

sk_wait_event() returns an error (-EPIPE) if disconnect() is called on the
socket waiting for the event. However, sk_stream_wait_connect() returns
success, i.e. zero, even if sk_wait_event() returns -EPIPE, so a function
that waits for a connection with sk_stream_wait_connect() may misbehave.

In the case of the above DCCP issue, dccp_sendmsg() is waiting for the
connection. If disconnect() is called in concurrently, the above issue
occurs.

This patch fixes the issue by returning error from sk_stream_wait_connect()
if sk_wait_event() fails.

Fixes: 419ce133ab92 ("tcp: allow again tcp_disconnect() when threads are waiting")
Signed-off-by: Shigeru Yoshida <syoshida@redhat.com>
---
net/core/stream.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/core/stream.c b/net/core/stream.c
index 96fbcb9bbb30..b16dfa568a2d 100644
--- a/net/core/stream.c
+++ b/net/core/stream.c
@@ -79,7 +79,7 @@ int sk_stream_wait_connect(struct sock *sk, long *timeo_p)
remove_wait_queue(sk_sleep(sk), &wait);
sk->sk_write_pending--;
} while (!done);
- return 0;
+ return done < 0 ? done : 0;
}
EXPORT_SYMBOL(sk_stream_wait_connect);

--
2.41.0