Fix sloppy wording around stricly less-than vs less or equal

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
diff --git a/include/mbedtls/net_sockets.h b/include/mbedtls/net_sockets.h
index 310b397..702e93f 100644
--- a/include/mbedtls/net_sockets.h
+++ b/include/mbedtls/net_sockets.h
@@ -157,7 +157,7 @@
  *
  * \note           The current implementation of this function uses
  *                 select() and returns an error if the file descriptor
- *                 is beyond \c FD_SETSIZE.
+ *                 is \c FD_SETSIZE or greater.
  *
  * \param ctx      Socket to check
  * \param rw       Bitflag composed of MBEDTLS_NET_POLL_READ and
@@ -242,7 +242,7 @@
  *
  * \note           The current implementation of this function uses
  *                 select() and returns an error if the file descriptor
- *                 is beyond \c FD_SETSIZE.
+ *                 is \c FD_SETSIZE or greater.
  *
  * \param ctx      Socket
  * \param buf      The buffer to write to
diff --git a/library/net_sockets.c b/library/net_sockets.c
index 375434a..ad1ac13 100644
--- a/library/net_sockets.c
+++ b/library/net_sockets.c
@@ -466,9 +466,9 @@
         return( MBEDTLS_ERR_NET_INVALID_CONTEXT );
 
     /* A limitation of select() is that it only works with file descriptors
-     * up to FD_SETSIZE. This is a limitation of the fd_set type. Error out
-     * early, because attempting to call FD_SET on a large file descriptor
-     * is a buffer overflow on typical platforms. */
+     * that are strictly less than FD_SETSIZE. This is a limitation of the
+     * fd_set type. Error out early, because attempting to call FD_SET on a
+     * large file descriptor is a buffer overflow on typical platforms. */
     if( fd >= FD_SETSIZE )
         return( MBEDTLS_ERR_NET_POLL_FAILED );
 
@@ -592,9 +592,9 @@
         return( MBEDTLS_ERR_NET_INVALID_CONTEXT );
 
     /* A limitation of select() is that it only works with file descriptors
-     * up to FD_SETSIZE. This is a limitation of the fd_set type. Error out
-     * early, because attempting to call FD_SET on a large file descriptor
-     * is a buffer overflow on typical platforms. */
+     * that are strictly less than FD_SETSIZE. This is a limitation of the
+     * fd_set type. Error out early, because attempting to call FD_SET on a
+     * large file descriptor is a buffer overflow on typical platforms. */
     if( fd >= FD_SETSIZE )
         return( MBEDTLS_ERR_NET_POLL_FAILED );