wutsocket fixes: select() handles timeout wrong, and poll() lacks a safety check (#428)

* - Fix select() to also update the fd_set arguments on timeout condition.
- Move the nfds argument restriction to the nsysnet side.
- Allow user-defined FD_SETSIZE, since newlib's fd_set allow custom sizes.
- Define __socklen_t_defined when socklen_t is typedefed.

* Added safety check for poll(): the nsysnet fd must fit in nsysnet_fd_set.

---------

Co-authored-by: Daniel K. O. (dkosmari) <none@none>

include/sys/select.h

@@ -1,5 +1,7 @@
 #pragma once
 
+#ifndef FD_SETSIZE
 #define FD_SETSIZE 32
+#endif
 
 #include_next <sys/select.h>

include/sys/socket.h

@@ -53,7 +53,11 @@
 #define SO_NOSLOWSTART 0x4000  // disable slowstart
 #define SO_RUSRBUF     0x10000 // enable somemopt provided memory for receive buffer
 
-typedef uint32_t socklen_t;
+#ifndef __socklen_t_defined
+typedef __socklen_t socklen_t;
+#define __socklen_t_defined
+#endif
+
 typedef uint16_t sa_family_t;
 
 struct sockaddr

libraries/wutsocket/poll.c

@@ -32,6 +32,10 @@ poll(struct pollfd *fds,
 
       if ((cnv_fd + 1) > cnv_nfds) {
          cnv_nfds = cnv_fd + 1;
+         if (cnv_nfds > NSYSNET_FD_SETSIZE) {
+            errno = EINVAL;
+            return -1;
+         }
       }
 
       if (fds[i].events & POLLIN) {

libraries/wutsocket/select.c

@@ -11,11 +11,6 @@ select(int nfds,
    nsysnet_fd_set cnv_rd, cnv_wr, cnv_ex;
    struct nsysnet_timeval cnv_timeout;
 
-   if (nfds > FD_SETSIZE) {
-      errno = EINVAL;
-      return -1;
-   }
-
    NSYSNET_FD_ZERO(&cnv_rd);
    NSYSNET_FD_ZERO(&cnv_wr);
    NSYSNET_FD_ZERO(&cnv_ex);
@@ -38,6 +33,10 @@ select(int nfds,
 
       if ((cnv_fd + 1) > cnv_nfds) {
          cnv_nfds = cnv_fd + 1;
+         if (cnv_nfds > NSYSNET_FD_SETSIZE) {
+            errno = EINVAL;
+            return -1;
+         }
       }
 
       if (rd_fd) {
@@ -67,8 +66,6 @@ select(int nfds,
       return rc;
    }
 
-   rc = 0;
-
    if (readfds) {
       FD_ZERO(readfds);
    }
@@ -79,6 +76,11 @@ select(int nfds,
       FD_ZERO(exceptfds);
    }
 
+   if (rc == 0)
+      return 0;
+
+   rc = 0;
+
    for (i = 0; i < nfds; i++) {
       int cnv_fd = __wut_get_nsysnet_fd(i);
       if (cnv_fd == -1) {