Fix the first couple of AddressSanitizer violations in usr.bin/top.

Avoid setting zero bytes beyond the length of the 'thisline' parameters
in i_process() and u_process(), and don't attempt to memset a negative
number of bytes.

MFC after:	1 week

1 files changed, 18 insertions, 4 deletions

diff --git a/usr.bin/top/display.c b/usr.bin/top/display.c
index 03277ea86cf2..b17be6e83569 100644
--- a/usr.bin/top/display.c
+++ b/usr.bin/top/display.c
@@ -829,7 +829,11 @@ i_process(int line, char *thisline)
     }
 
     /* truncate the line to conform to our current screen width */
-    thisline[screen_width] = '\0';
+    int len = strlen(thisline);
+    if (screen_width < len)
+    {
+	thisline[screen_width] = '\0';
+    }
 
     /* write the line out */
     fputs(thisline, stdout);
@@ -839,7 +843,10 @@ i_process(int line, char *thisline)
     p = stpcpy(base, thisline);
 
     /* zero fill the rest of it */
-    memset(p, 0, screen_width - (p - base));
+    if (p - base < screen_width)
+    {
+	memset(p, 0, screen_width - (p - base));
+    }
 }
 
 void
@@ -853,7 +860,11 @@ u_process(int line, char *newline)
     bufferline = &screenbuf[lineindex(line)];
 
     /* truncate the line to conform to our current screen width */
-    newline[screen_width] = '\0';
+    int len = strlen(newline);
+    if (screen_width < len)
+    {
+	newline[screen_width] = '\0';
+    }
 
     /* is line higher than we went on the last display? */
     if (line >= last_hi)
@@ -878,7 +889,10 @@ u_process(int line, char *newline)
 	optr = stpcpy(bufferline, newline);
 
 	/* zero fill the rest of it */
-	memset(optr, 0, screen_width - (optr - bufferline));
+	if (optr - bufferline < screen_width)
+	{
+	    memset(optr, 0, screen_width - (optr - bufferline));
+	}
     }
     else
     {