[Midnightbsd-cvs] src [9193] trunk/sys/amd64/amd64/sys_machdep.c: fix a security issue.

[laffer1 at midnightbsd.org]

Revision: 9193
          http://svnweb.midnightbsd.org/src/?rev=9193
Author:   laffer1
Date:     2016-10-25 18:55:42 -0400 (Tue, 25 Oct 2016)
Log Message:
-----------
fix a security issue. obtained from freebsd

Modified Paths:
--------------
    trunk/sys/amd64/amd64/sys_machdep.c

Modified: trunk/sys/amd64/amd64/sys_machdep.c
===================================================================
--- trunk/sys/amd64/amd64/sys_machdep.c	2016-10-25 22:35:44 UTC (rev 9192)
+++ trunk/sys/amd64/amd64/sys_machdep.c	2016-10-25 22:55:42 UTC (rev 9193)
@@ -612,6 +612,8 @@
 		largest_ld = uap->start + uap->num;
 		if (largest_ld > max_ldt_segment)
 			largest_ld = max_ldt_segment;
+		if (largest_ld < uap->start)
+			return (EINVAL);
 		i = largest_ld - uap->start;
 		mtx_lock(&dt_lock);
 		bzero(&((struct user_segment_descriptor *)(pldt->ldt_base))
@@ -624,7 +626,8 @@
 		/* verify range of descriptors to modify */
 		largest_ld = uap->start + uap->num;
 		if (uap->start >= max_ldt_segment ||
-		    largest_ld > max_ldt_segment)
+		    largest_ld > max_ldt_segment ||
+		    largest_ld < uap->start)
 			return (EINVAL);
 	}