smb: client: Fix next buffer leak in receive_encrypted_standard()

commit 1c6267a upstream.

receive_encrypted_standard() allocates next_buffer before checking
whether the number of compound PDUs already reached MAX_COMPOUND. If
the limit check fails, the function returns immediately and the newly
allocated next_buffer is not assigned to server->smallbuf/server->bigbuf,
making it leaked.

Move the MAX_COMPOUND check before allocating next_buffer.

Fixes: b24df3e ("cifs: update receive_encrypted_standard to handle compounded responses")
Cc: stable@vger.kernel.org
Signed-off-by: Haoxiang Li <haoxiang_li2024@163.com>
Signed-off-by: Steve French <stfrench@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: Haoxiang Li

fs/smb/client/smb2ops.c

@@ -5096,6 +5096,12 @@ receive_encrypted_standard(struct TCP_Server_Info *server,
 one_more:
 	shdr = (struct smb2_hdr *)buf;
 	next_cmd = le32_to_cpu(shdr->NextCommand);
+
+	if (*num_mids >= MAX_COMPOUND) {
+		cifs_server_dbg(VFS, "too many PDUs in compound\n");
+		return -1;
+	}
+
 	if (next_cmd) {
 		if (WARN_ON_ONCE(next_cmd > pdu_length))
 			return -1;
@@ -5119,10 +5125,6 @@ receive_encrypted_standard(struct TCP_Server_Info *server,
 		mid_entry->resp_buf_size = server->pdu_size;
 	}
 
-	if (*num_mids >= MAX_COMPOUND) {
-		cifs_server_dbg(VFS, "too many PDUs in compound\n");
-		return -1;
-	}
 	bufs[*num_mids] = buf;
 	mids[(*num_mids)++] = mid_entry;