sd-dhcp: make sure we can not fill options so much that there is no space for END

2 files changed, 5 insertions, 1 deletions

diff --git a/src/libsystemd-network/dhcp-option.c b/src/libsystemd-network/dhcp-option.c
index 68950923dd..24f678c100 100644
--- a/src/libsystemd-network/dhcp-option.c
+++ b/src/libsystemd-network/dhcp-option.c
@@ -31,6 +31,10 @@ int dhcp_option_append(uint8_t options[], size_t size, size_t *offset,
         assert(options);
         assert(offset);
 
+        if (code != DHCP_OPTION_END)
+                /* always make sure there is space for an END option */
+                size --;
+
         switch (code) {
 
         case DHCP_OPTION_PAD:
diff --git a/src/libsystemd-network/test-dhcp-option.c b/src/libsystemd-network/test-dhcp-option.c
index eaf6a535e6..3dd7102d82 100644
--- a/src/libsystemd-network/test-dhcp-option.c
+++ b/src/libsystemd-network/test-dhcp-option.c
@@ -85,7 +85,7 @@ static void test_invalid_buffer_length(void)
 static void test_message_init(void)
 {
         _cleanup_free_ DHCPMessage *message = NULL;
-        size_t optlen = 3, optoffset;
+        size_t optlen = 4, optoffset;
         size_t len = sizeof(DHCPMessage) + optlen;
         uint8_t *magic;