rxrpc, afs: Fix missing error pointer check after rxrpc_kernel_lookup_peer()

rxrpc_kernel_lookup_peer() can also return error pointers in addition to
NULL, so just checking for NULL is not sufficient.

Fix this by:

 (1) Changing rxrpc_kernel_lookup_peer() to return -ENOMEM rather than NULL
     on allocation failure.

 (2) Making the callers in afs use IS_ERR() and PTR_ERR() to pass on the
     error code returned.

Fixes: 72904d7 ("rxrpc, afs: Allow afs to pin rxrpc_peer objects")
Signed-off-by: Miaoqian Lin <[email protected]>
Co-developed-by: David Howells <[email protected]>
Signed-off-by: David Howells <[email protected]>
cc: Marc Dionne <[email protected]>
cc: Simon Horman <[email protected]>
cc: [email protected]
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Jakub Kicinski <[email protected]>

Author: Yuuoniy

fs/afs/addr_list.c

@@ -298,8 +298,8 @@ int afs_merge_fs_addr4(struct afs_net *net, struct afs_addr_list *alist,
 	srx.transport.sin.sin_addr.s_addr = xdr;
 
 	peer = rxrpc_kernel_lookup_peer(net->socket, &srx, GFP_KERNEL);
-	if (!peer)
-		return -ENOMEM;
+	if (IS_ERR(peer))
+		return PTR_ERR(peer);
 
 	for (i = 0; i < alist->nr_ipv4; i++) {
 		if (peer == alist->addrs[i].peer) {
@@ -342,8 +342,8 @@ int afs_merge_fs_addr6(struct afs_net *net, struct afs_addr_list *alist,
 	memcpy(&srx.transport.sin6.sin6_addr, xdr, 16);
 
 	peer = rxrpc_kernel_lookup_peer(net->socket, &srx, GFP_KERNEL);
-	if (!peer)
-		return -ENOMEM;
+	if (IS_ERR(peer))
+		return PTR_ERR(peer);
 
 	for (i = alist->nr_ipv4; i < alist->nr_addrs; i++) {
 		if (peer == alist->addrs[i].peer) {

net/rxrpc/af_rxrpc.c

@@ -267,20 +267,22 @@ static int rxrpc_listen(struct socket *sock, int backlog)
  * Lookup or create a remote transport endpoint record for the specified
  * address.
  *
- * Return: The peer record found with a reference, %NULL if no record is found
- * or a negative error code if the address is invalid or unsupported.
+ * Return: The peer record found with a reference or a negative error code if
+ * the address is invalid or unsupported.
  */
 struct rxrpc_peer *rxrpc_kernel_lookup_peer(struct socket *sock,
 					    struct sockaddr_rxrpc *srx, gfp_t gfp)
 {
+	struct rxrpc_peer *peer;
 	struct rxrpc_sock *rx = rxrpc_sk(sock->sk);
 	int ret;
 
 	ret = rxrpc_validate_address(rx, srx, sizeof(*srx));
 	if (ret < 0)
 		return ERR_PTR(ret);
 
-	return rxrpc_lookup_peer(rx->local, srx, gfp);
+	peer = rxrpc_lookup_peer(rx->local, srx, gfp);
+	return peer ?: ERR_PTR(-ENOMEM);
 }
 EXPORT_SYMBOL(rxrpc_kernel_lookup_peer);