[newlib-cygwin] Cygwin: console: Prevent buffer overrun.

[Corinna Vinschen]

https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;h=750cd6e5b2bb4ab74de7d2f9e0afb6dd0c005cf1

commit 750cd6e5b2bb4ab74de7d2f9e0afb6dd0c005cf1
Author: Takashi Yano <takashi.yano@nifty.ne.jp>
Date:   Mon Mar 2 10:12:56 2020 +0900

    Cygwin: console: Prevent buffer overrun.
    
    - This patch prevent potential buffer overrun in the code handling
      escape sequences.

Diff:
---
 winsup/cygwin/fhandler_console.cc | 18 ++++++++----------
 1 file changed, 8 insertions(+), 10 deletions(-)

diff --git a/winsup/cygwin/fhandler_console.cc b/winsup/cygwin/fhandler_console.cc
index 9c5b801..8b46877 100644
--- a/winsup/cygwin/fhandler_console.cc
+++ b/winsup/cygwin/fhandler_console.cc
@@ -3094,7 +3094,8 @@ fhandler_console::write (const void *vsrc, size_t len)
 	case gotarg1:
 	  if (isdigit (*src))
 	    {
-	      con.args[con.nargs] = con.args[con.nargs] * 10 + *src - '0';
+	      if (con.nargs < MAXARGS)
+		con.args[con.nargs] = con.args[con.nargs] * 10 + *src - '0';
 	      wpbuf_put (*src);
 	      src++;
 	    }
@@ -3102,9 +3103,8 @@ fhandler_console::write (const void *vsrc, size_t len)
 	    {
 	      wpbuf_put (*src);
 	      src++;
-	      con.nargs++;
-	      if (con.nargs > MAXARGS)
-		con.nargs--;
+	      if (con.nargs < MAXARGS)
+		con.nargs++;
 	    }
 	  else if (*src == ' ')
 	    {
@@ -3117,9 +3117,8 @@ fhandler_console::write (const void *vsrc, size_t len)
 	    con.state = gotcommand;
 	  break;
 	case gotcommand:
-	  con.nargs ++;
-	  if (con.nargs > MAXARGS)
-	    con.nargs--;
+	  if (con.nargs < MAXARGS)
+	    con.nargs++;
 	  char_command (*src++);
 	  con.state = normal;
 	  wpixput = 0;
@@ -3183,9 +3182,8 @@ fhandler_console::write (const void *vsrc, size_t len)
 	    {
 	      con.state = gotarg1;
 	      wpbuf_put (*src);
-	      con.nargs++;
-	      if (con.nargs > MAXARGS)
-		con.nargs--;
+	      if (con.nargs < MAXARGS)
+		con.nargs++;
 	      src++;
 	    }
 	  else if (isalpha (*src))