diff --git a/source/client/client.c b/source/client/client.c

index e87623a..2bbc12a 100644

--- a/source/client/client.c

+++ b/source/client/client.c

@@ -3611,8 +3611,10 @@ static void readline_callback(void)

  again:

-	if (cli->fd == -1)

+	if (cli->fd < 0 || cli->fd >= FD_SETSIZE) {

+		errno = EBADF;

 		return;

+	}

 	FD_ZERO(&fds);

 	FD_SET(cli->fd,&fds);

diff --git a/source/client/smbctool.c b/source/client/smbctool.c

index a18505b..c38ea48 100644

--- a/source/client/smbctool.c

+++ b/source/client/smbctool.c

@@ -3289,8 +3289,10 @@ static void readline_callback(void)

  again:

-	if (cli->fd == -1)

+	if (cli->fd < 0 || cli->fd >= FD_SETSIZE) {

+		errno = EBADF;

 		return;

+	}

 	FD_ZERO(&fds);

 	FD_SET(cli->fd,&fds);

diff --git a/source/lib/events.c b/source/lib/events.c

index fadb15e..c2e6d17 100644

--- a/source/lib/events.c

+++ b/source/lib/events.c

@@ -153,6 +153,11 @@ struct fd_event *event_add_fd(struct event_context *event_ctx,

 {

 	struct fd_event *fde;

+	if (fd < 0 || fd >= FD_SETSIZE) {

+		errno = EBADF;

+		return NULL;

+	}

+

 	if (!(fde = TALLOC_P(mem_ctx, struct fd_event))) {

 		return NULL;

 	}

@@ -198,6 +203,14 @@ void event_add_to_select_args(struct event_context *event_ctx,

 	struct timeval diff;

 	for (fde = event_ctx->fd_events; fde; fde = fde->next) {

+		if (fde->fd < 0 || fde->fd >= FD_SETSIZE) {

+			/* We ignore here, as it shouldn't be

+			   possible to add an invalid fde->fd

+			   but we don't want FD_SET to see an

+			   invalid fd. */

+			continue;

+		}

+

 		if (fde->flags & EVENT_FD_READ) {

 			FD_SET(fde->fd, read_fds);

 		}

diff --git a/source/lib/readline.c b/source/lib/readline.c

index 24d16ea..90d06be 100644

--- a/source/lib/readline.c

+++ b/source/lib/readline.c

@@ -69,6 +69,11 @@ static char *smb_readline_replacement(const char *prompt, void (*callback)(void)

 		timeout.tv_sec = 5;

 		timeout.tv_usec = 0;

+		if (fd < 0 || fd >= FD_SETSIZE) {

+			errno = EBADF;

+			break;

+		}

+

 		FD_ZERO(&fds);

 		FD_SET(fd,&fds);

@@ -79,6 +84,7 @@ static char *smb_readline_replacement(co

 		if (callback)

 			callback();

 	}

+	return NULL;

 }

 /****************************************************************************

diff --git a/source/lib/select.c b/source/lib/select.c

index f63221f..13bf29c 100644

--- a/source/lib/select.c

+++ b/source/lib/select.c

@@ -61,6 +61,11 @@ int sys_select(int maxfd, fd_set *readfds, fd_set *writefds, fd_set *errorfds, s

 	if (initialised != sys_getpid()) {

 		pipe(select_pipe);

+		if (select_pipe[0] < 0 || select_pipe[0] >= FD_SETSIZE) {

+			errno = EBADF;

+			return -1;

+		}

+

 		/*

 		 * These next two lines seem to fix a bug with the Linux

 		 * 2.0.x kernel (and probably other UNIXes as well) where

diff --git a/source/lib/util_sock.c b/source/lib/util_sock.c

index 4715ca7..158d95e 100644

--- a/source/lib/util_sock.c

+++ b/source/lib/util_sock.c

@@ -452,6 +452,12 @@ ssize_t read_socket_with_timeout(int fd,char *buf,size_t mincnt,size_t maxcnt,un

 	timeout.tv_usec = (long)(1000 * (time_out % 1000));

 	for (nread=0; nread < mincnt; ) {      

+		if (fd < 0 || fd >= FD_SETSIZE) {

+			errno = EBADF;

+			smb_read_error = READ_ERROR;

+			return -1;

+		}

+

 		FD_ZERO(&fds);

 		FD_SET(fd,&fds);

@@ -944,7 +950,7 @@ BOOL open_any_socket_out(struct sockaddr_in *addrs, int num_addrs,

 	for (i=0; i<num_addrs; i++) {

 		sockets[i] = socket(PF_INET, SOCK_STREAM, 0);

-		if (sockets[i] < 0)

+		if (sockets[i] < 0 || sockets[i] >= FD_SETSIZE)

 			goto done;

 		set_blocking(sockets[i], False);

 	}

@@ -992,8 +998,10 @@ BOOL open_any_socket_out(struct sockaddr_in *addrs, int num_addrs,

 	FD_ZERO(&r_fds);

 	for (i=0; i<num_addrs; i++) {

-		if (sockets[i] == -1)

+		if (sockets[i] < 0 || sockets[i] >= FD_SETSIZE) {

+			/* This cannot happen - ignore if so. */

 			continue;

+		}

 		FD_SET(sockets[i], &wr_fds);

 		FD_SET(sockets[i], &r_fds);

 		if (sockets[i]>maxfd)

@@ -1012,9 +1020,9 @@ BOOL open_any_socket_out(struct sockaddr_in *addrs, int num_addrs,

 		goto next_round;

 	for (i=0; i<num_addrs; i++) {

-

-		if (sockets[i] == -1)

+		if (sockets[i] < 0 || sockets[i] >= FD_SETSIZE) {

 			continue;

+		}

 		/* Stevens, Network Programming says that if there's a

 		 * successful connect, the socket is only writable. Upon an

diff --git a/source/libaddns/dnssock.c b/source/libaddns/dnssock.c

index 6ceefb4..00b8db2 100644

--- a/source/libaddns/dnssock.c

+++ b/source/libaddns/dnssock.c

@@ -219,7 +219,11 @@ static DNS_ERROR read_all(int fd, uint8 *data, size_t len)

 	while (total < len) {

 		ssize_t ret;

 		int fd_ready;

-		

+

+		if (fd < 0 || fd >= FD_SETSIZE) {

+			return ERROR_DNS_SOCKET_ERROR;

+		}

+

 		FD_ZERO( &rfds );

 		FD_SET( fd, &rfds );

diff --git a/source/libsmb/nmblib.c b/source/libsmb/nmblib.c

index 641473b..97ff61f 100644

--- a/source/libsmb/nmblib.c

+++ b/source/libsmb/nmblib.c

@@ -1011,6 +1011,11 @@ struct packet_struct *receive_packet(int fd,enum packet_type type,int t)

 	struct timeval timeout;

 	int ret;

+	if (fd < 0 || fd >= FD_SETSIZE) {

+		errno = EBADF;

+		return NULL;

+	}

+

 	FD_ZERO(&fds);

 	FD_SET(fd,&fds);

 	timeout.tv_sec = t/1000;

diff --git a/source/nmbd/nmbd_packets.c b/source/nmbd/nmbd_packets.c

index 97a81fe..52133f6 100644

--- a/source/nmbd/nmbd_packets.c

+++ b/source/nmbd/nmbd_packets.c

@@ -1678,7 +1678,7 @@ static BOOL create_listen_fdset(fd_set **ppset, int **psock_array, int *listen_n

 	for (subrec = FIRST_SUBNET; subrec; subrec = NEXT_SUBNET_EXCLUDING_UNICAST(subrec))

 		count++;

-	if((count*2) + 2 > FD_SETSIZE) {

+	if((count*2) + 2 >= FD_SETSIZE) {

 		DEBUG(0,("create_listen_fdset: Too many file descriptors needed (%d). We can \

 only use %d.\n", (count*2) + 2, FD_SETSIZE));

 		SAFE_FREE(pset);

@@ -1694,24 +1694,44 @@ only use %d.\n", (count*2) + 2, FD_SETSIZE));

 	FD_ZERO(pset);

 	/* Add in the broadcast socket on 137. */

+	if (ClientNMB < 0 || ClientNMB >= FD_SETSIZE) {

+		errno = EBADF;

+		SAFE_FREE(pset);

+		return True;

+	}

+

 	FD_SET(ClientNMB,pset);

 	sock_array[num++] = ClientNMB;

 	*maxfd = MAX( *maxfd, ClientNMB);

 	/* Add in the 137 sockets on all the interfaces. */

 	for (subrec = FIRST_SUBNET; subrec; subrec = NEXT_SUBNET_EXCLUDING_UNICAST(subrec)) {

+		if (subrec->nmb_sock < 0 || subrec->nmb_sock >= FD_SETSIZE) {

+			/* We have to ignore sockets outside FD_SETSIZE. */

+			continue;

+		}

 		FD_SET(subrec->nmb_sock,pset);

 		sock_array[num++] = subrec->nmb_sock;

 		*maxfd = MAX( *maxfd, subrec->nmb_sock);

 	}

 	/* Add in the broadcast socket on 138. */

+	if (ClientDGRAM < 0 || ClientDGRAM >= FD_SETSIZE) {

+		errno = EBADF;

+		SAFE_FREE(pset);

+		return True;

+	}

+

 	FD_SET(ClientDGRAM,pset);

 	sock_array[num++] = ClientDGRAM;

 	*maxfd = MAX( *maxfd, ClientDGRAM);

 	/* Add in the 138 sockets on all the interfaces. */

 	for (subrec = FIRST_SUBNET; subrec; subrec = NEXT_SUBNET_EXCLUDING_UNICAST(subrec)) {

+		if (subrec->dgram_sock < 0 || subrec->dgram_sock >= FD_SETSIZE) {

+			/* We have to ignore sockets outside FD_SETSIZE. */

+			continue;

+		}

 		FD_SET(subrec->dgram_sock,pset);

 		sock_array[num++] = subrec->dgram_sock;

 		*maxfd = MAX( *maxfd, subrec->dgram_sock);

@@ -1760,7 +1780,7 @@ BOOL listen_for_packets(BOOL run_election)

 #ifndef SYNC_DNS

 	dns_fd = asyncdns_fd();

-	if (dns_fd != -1) {

+	if (dns_fd != -1 && dns_fd < FD_SETSIZE) {

 		FD_SET(dns_fd, &fds);

 		maxfd = MAX( maxfd, dns_fd);

 	}

diff --git a/source/nsswitch/wb_common.c b/source/nsswitch/wb_common.c

index bae54f2..401adb9 100644

--- a/source/nsswitch/wb_common.c

+++ b/source/nsswitch/wb_common.c

@@ -249,6 +249,12 @@ static int winbind_named_pipe_sock(const char *dir)

 		switch (errno) {

 			case EINPROGRESS:

+

+				if (fd < 0 || fd >= FD_SETSIZE) {

+					errno = EBADF;

+					goto error_out;

+				}

+

 				FD_ZERO(&w_fds);

 				FD_SET(fd, &w_fds);

 				tv.tv_sec = CONNECT_TIMEOUT - wait_time;

@@ -378,7 +384,13 @@ int write_sock(void *buffer, int count, int recursing, int need_priv)

 	while(nwritten < count) {

 		struct timeval tv;

 		fd_set r_fds;

-		

+

+		if (winbindd_fd < 0 || winbindd_fd >= FD_SETSIZE) {

+			errno = EBADF;

+			close_sock();

+			return -1;

+		}

+

 		/* Catch pipe close on other end by checking if a read()

 		   call would not block by calling select(). */

@@ -430,7 +442,8 @@ static int read_sock(void *buffer, int count)

 	int nread = 0;

 	int total_time = 0, selret;

-	if (winbindd_fd == -1) {

+	if (winbindd_fd < 0 || winbindd_fd >= FD_SETSIZE) {

+		errno = EBADF;

 		return -1;

 	}

diff --git a/source/nsswitch/winbindd.c b/source/nsswitch/winbindd.c

index 48b94f2..ac6aa8c 100644

--- a/source/nsswitch/winbindd.c

+++ b/source/nsswitch/winbindd.c

@@ -772,7 +772,8 @@ static void process_loop(void)

 	listen_sock = open_winbindd_socket();

 	listen_priv_sock = open_winbindd_priv_socket();

-	if (listen_sock == -1 || listen_priv_sock == -1) {

+	if (listen_sock < 0 || listen_sock >= FD_SETSIZE ||

+			listen_priv_sock < 0 || listen_priv_sock >= FD_SETSIZE) {

 		perror("open_winbind_socket");

 		exit(1);

 	}

@@ -798,6 +799,9 @@ static void process_loop(void)

 	maxfd = MAX(listen_sock, listen_priv_sock);

+	/* We check the range for listen_sock and

+	   listen_priv_sock above. */

+

 	FD_ZERO(&r_fds);

 	FD_ZERO(&w_fds);

 	FD_SET(listen_sock, &r_fds);

@@ -829,6 +833,12 @@ static void process_loop(void)

 	}

 	for (ev = fd_events; ev; ev = ev->next) {

+		if (ev->fd < 0 || ev->fd >= FD_SETSIZE) {

+			/* Ignore here - event_add_to_select_args

+			   should make this impossible. */

+			continue;

+		}

+

 		if (ev->flags & EVENT_FD_READ) {

 			FD_SET(ev->fd, &r_fds);

 			maxfd = MAX(ev->fd, maxfd);

diff --git a/source/nsswitch/winbindd_dual.c b/source/nsswitch/winbindd_dual.c

index f976eba..2e3abe2 100644

--- a/source/nsswitch/winbindd_dual.c

+++ b/source/nsswitch/winbindd_dual.c

@@ -988,6 +988,12 @@ static BOOL fork_domain_child(struct winbindd_child *child)

 		return False;

 	}

+	if (fdpair[0] < 0 || fdpair[0] >= FD_SETSIZE) {

+		DEBUG(0, ("fork_domain_child: bad fd range (%d)\n", fdpair[0]));

+		errno = EBADF;

+		return False;

+	}

+

 	ZERO_STRUCT(state);

 	state.pid = sys_getpid();

@@ -1130,6 +1136,7 @@ static BOOL fork_domain_child(struct winbindd_child *child)

 		message_dispatch();

 		FD_ZERO(&read_fds);

+		/* We check state.sock against FD_SETSIZE above. */

 		FD_SET(state.sock, &read_fds);

 		ret = sys_select(state.sock + 1, &read_fds, NULL, NULL, tp);

diff --git a/source/smbd/oplock.c b/source/smbd/oplock.c

index 54c9492..60ddfb7 100644

--- a/source/smbd/oplock.c

+++ b/source/smbd/oplock.c

@@ -240,7 +240,10 @@ BOOL downgrade_oplock(files_struct *fsp)

 int oplock_notify_fd(void)

 {

 	if (koplocks) {

-		return koplocks->notification_fd;

+		int fd = koplocks->notification_fd;

+		if (fd < 0 || fd >= FD_SETSIZE) {

+			return -1;

+		}

 	}

 	return -1;

diff --git a/source/smbd/oplock_irix.c b/source/smbd/oplock_irix.c

index c1159cd..b822cb8 100644

--- a/source/smbd/oplock_irix.c

+++ b/source/smbd/oplock_irix.c

@@ -247,6 +247,7 @@ static BOOL irix_oplock_msg_waiting(fd_set *fds)

 	 * we need to ignore any signals. */

 	FD_ZERO(&myfds);

+	/* We check oplock_pipe_read is in the correct range below. */

 	FD_SET(oplock_pipe_read, &myfds);

 	to = timeval_set(0, 0);

@@ -272,6 +273,11 @@ struct kernel_oplocks *irix_init_kernel_oplocks(void)

 		return False;

 	}

+	if (pfd[0] < 0 || pfd[0] >= FD_SETSIZE) {

+		DEBUG(0,("setup_kernel_oplock_pipe: fd out of range.\n"));

+		return False;

+	}

+

 	oplock_pipe_read = pfd[0];

 	oplock_pipe_write = pfd[1];

diff --git a/source/smbd/process.c b/source/smbd/process.c

index e861e16..a81d169 100644

--- a/source/smbd/process.c

+++ b/source/smbd/process.c

@@ -320,7 +320,7 @@ static void async_processing(fd_set *pfds)

 static int select_on_fd(int fd, int maxfd, fd_set *fds)

 {

-	if (fd != -1) {

+	if (fd != -1 && fd < FD_SETSIZE) {

 		FD_SET(fd, fds);

 		maxfd = MAX(maxfd, fd);

 	}

diff --git a/source/smbd/server.c b/source/smbd/server.c

index 9f13c32..de3e5b1 100644

--- a/source/smbd/server.c

+++ b/source/smbd/server.c

@@ -184,7 +184,13 @@ static BOOL open_sockets_inetd(void)

 	/* Started from inetd. fd 0 is the socket. */

 	/* We will abort gracefully when the client or remote system 

 	   goes away */

-	smbd_set_server_fd(dup(0));

+	int fd = dup(0);

+

+	if (fd < 0 || fd >= FD_SETSIZE) {

+		return false;

+	}

+

+	smbd_set_server_fd(fd);

 	/* close our standard file descriptors */

 	close_low_fds(False); /* Don't close stderr */

@@ -371,8 +377,9 @@ static BOOL open_sockets_smbd(BOOL is_daemon, BOOL interactive, const char *smb_

 					continue;

 				}

 				s = fd_listenset[num_sockets] = open_socket_in(SOCK_STREAM, port, 0, ifip->s_addr, True);

-				if(s == -1)

+				if (s < 0 || s >= FD_SETSIZE) {

 					return False;

+				}

 				/* ready to listen */

 				set_socket_options(s,"SO_KEEPALIVE"); 

@@ -411,8 +418,9 @@ static BOOL open_sockets_smbd(BOOL is_daemon, BOOL interactive, const char *smb_

 			/* open an incoming socket */

 			s = open_socket_in(SOCK_STREAM, port, 0,

 					   interpret_addr(lp_socket_address()),True);

-			if (s == -1)

-				return(False);

+			if (s < 0 || s >= FD_SETSIZE) {

+				return False;

+			}

 			/* ready to listen */

 			set_socket_options(s,"SO_KEEPALIVE"); 

@@ -509,6 +517,7 @@ static BOOL open_sockets_smbd(BOOL is_daemon, BOOL interactive, const char *smb_

 			struct sockaddr addr;

 			socklen_t in_addrlen = sizeof(addr);

 			pid_t child = 0;

+			int fd;

 			s = -1;

 			for(i = 0; i < num_sockets; i++) {

@@ -521,17 +530,22 @@ static BOOL open_sockets_smbd(BOOL is_daemon, BOOL interactive, const char *smb_

 				}

 			}

-			smbd_set_server_fd(accept(s,&addr,&in_addrlen));

-			

-			if (smbd_server_fd() == -1 && errno == EINTR)

+			fd = accept(s,&addr,&in_addrlen);

+			if (fd == -1 && errno == EINTR)

 				continue;

-			

-			if (smbd_server_fd() == -1) {

+			if (fd == -1) {

 				DEBUG(0,("open_sockets_smbd: accept: %s\n",

 					 strerror(errno)));

 				continue;

 			}

+			if (fd < 0 || fd >= FD_SETSIZE) {

+				DEBUG(2,("open_sockets_smbd: bad fd %d\n",

+					fd ));

+				continue;

+			}

+			smbd_set_server_fd(fd);

+			

 			/* Ensure child is set to blocking mode */

 			set_blocking(smbd_server_fd(),True);

diff --git a/source/utils/smbfilter.c b/source/utils/smbfilter.c

index 2152e53..8bad730 100644

--- a/source/utils/smbfilter.c

+++ b/source/utils/smbfilter.c

@@ -133,8 +133,8 @@ static void filter_child(int c, struct in_addr dest_ip)

 		int num;

 		FD_ZERO(&fds);

-		if (s != -1) FD_SET(s, &fds);

-		if (c != -1) FD_SET(c, &fds);

+		if (s >= 0 && s < FD_SETSIZE) FD_SET(s, &fds);

+		if (c >= 0 && c < FD_SETSIZE) FD_SET(c, &fds);

 		num = sys_select_intr(MAX(s+1, c+1),&fds,NULL,NULL,NULL);

 		if (num <= 0) continue;

@@ -197,6 +197,10 @@ static void start_filter(char *desthost)

 		struct sockaddr addr;

 		socklen_t in_addrlen = sizeof(addr);

+		if (s < 0 || s >= FD_SETSIZE) {

+			break;

+		}

+

 		FD_ZERO(&fds);

 		FD_SET(s, &fds);