[PATCH mptcp-net v2] selftests: mptcp: fix an UAF in mptcp_connect.c

From: Gang Yan <[email protected]>

At the end of 'sock_connect_mptcp()', it calls 'freeaddrinfo(addr)',
the 'peer' pointer (which points into 'addr') remains. Later, the main
loop uses this peer pointer for reconnection attempts. If the memory has
been freed and reused, the address data could be overwritten, resulting
in an invalid remote address.

This patch keeps the addrinfo list allocated for the whole process
lifetime so "peer" remains valid across reconnects; the memory will be
released at exit() time.

Fixes: 05be5e273c84 ("selftests: mptcp: add disconnect tests")
Suggested-by: Paolo Abeni <[email protected]>
Signed-off-by: Gang Yan <[email protected]>
---
Changelog:
v2:
  - make fix as paolo suggested, and using AI to simplify the comment.
v1:
  Link: https://patchwork.kernel.org/project/mptcp/patch/[email protected]/

---
 tools/testing/selftests/net/mptcp/mptcp_connect.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/net/mptcp/mptcp_connect.c b/tools/testing/selftests/net/mptcp/mptcp_connect.c
index ea4cb6c1bd5e..178d98d91fea 100644
--- a/tools/testing/selftests/net/mptcp/mptcp_connect.c
+++ b/tools/testing/selftests/net/mptcp/mptcp_connect.c
@@ -381,6 +381,9 @@ static int sock_connect_mptcp(const char * const remoteaddr,
 
 	hints.ai_family = pf;
 
+	/* Keep the resolved address alive for the whole execution: it is
+	 * used again when reconnecting, and will be released at exit time.
+	 */
 	xgetaddrinfo(remoteaddr, port, &hints, &addr);
 	for (a = addr; a; a = a->ai_next) {
 		sock = socket(a->ai_family, a->ai_socktype, proto);
@@ -421,7 +424,6 @@ static int sock_connect_mptcp(const char * const remoteaddr,
 		sock = -1;
 	}
 
-	freeaddrinfo(addr);
 	if (sock != -1)
 		SOCK_TEST_TCPULP(sock, proto);
 	return sock;
-- 
2.43.0