udhcpd: check config file for bad IP ranges (start > end)

function                                             old     new   delta
.rodata                                           104209  104238     +29
read_config                                          208     225     +17
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 2/0 up/down: 46/0)               Total: 46 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

1 files changed, 6 insertions, 4 deletions

diff --git a/networking/udhcp/dhcpd.c b/networking/udhcp/dhcpd.c
index eef8a3b59..b67dfc3bc 100644
--- a/networking/udhcp/dhcpd.c
+++ b/networking/udhcp/dhcpd.c
@@ -451,6 +451,8 @@ static NOINLINE void read_config(const char *file)
 
         server_data.start_ip = ntohl(server_data.start_ip);
         server_data.end_ip = ntohl(server_data.end_ip);
+        if (server_data.start_ip > server_data.end_ip)
+                bb_error_msg_and_die("bad start/end IP range in %s", file);
 }
 
 static void write_leases(void)
@@ -858,7 +860,6 @@ int udhcpd_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 int udhcpd_main(int argc UNUSED_PARAM, char **argv)
 {
         int server_socket = -1, retval;
-        uint8_t *state;
         unsigned timeout_end;
         unsigned num_ips;
         unsigned opt;
@@ -966,6 +967,7 @@ int udhcpd_main(int argc UNUSED_PARAM, char **argv)
                 struct dhcp_packet packet;
                 int bytes;
                 int tv;
+                uint8_t *msg_type;
                 uint8_t *server_id_opt;
                 uint8_t *requested_ip_opt;
                 uint32_t requested_nip;
@@ -1040,8 +1042,8 @@ int udhcpd_main(int argc UNUSED_PARAM, char **argv)
                         bb_info_msg("not a REQUEST%s", ", ignoring packet");
                         continue;
                 }
-                state = udhcp_get_option(&packet, DHCP_MESSAGE_TYPE);
-                if (state == NULL || state[0] < DHCP_MINTYPE || state[0] > DHCP_MAXTYPE) {
+                msg_type = udhcp_get_option(&packet, DHCP_MESSAGE_TYPE);
+                if (!msg_type || msg_type[0] < DHCP_MINTYPE || msg_type[0] > DHCP_MAXTYPE) {
                         bb_info_msg("no or bad message type option%s", ", ignoring packet");
                         continue;
                 }
@@ -1077,7 +1079,7 @@ int udhcpd_main(int argc UNUSED_PARAM, char **argv)
                         move_from_unaligned32(requested_nip, requested_ip_opt);
                 }
 
-                switch (state[0]) {
+                switch (msg_type[0]) {
 
                 case DHCPDISCOVER:
                         log1("received %s", "DISCOVER");