svn commit: r190145 - head/sys/kern

[Konstantin Belousov]

Author: kib
Date: Fri Mar 20 11:08:57 2009
New Revision: 190145
URL: http://svn.freebsd.org/changeset/base/190145

Log:
  Do not underflow the buffer and then report the problem. Check for the
  condition before the buffer write.
  Also, since buflen is unsigned, previous check was ignored.
  
  Reviewed by:	marcus
  Tested by:	pho

Modified:
  head/sys/kern/vfs_cache.c

Modified: head/sys/kern/vfs_cache.c
==============================================================================
--- head/sys/kern/vfs_cache.c	Fri Mar 20 11:03:55 2009	(r190144)
+++ head/sys/kern/vfs_cache.c	Fri Mar 20 11:08:57 2009	(r190145)
@@ -970,13 +970,13 @@ vn_fullpath1(struct thread *td, struct v
 			if (error)
 				return (error);
 		}
-		*--bp = '/';
-		buflen--;
-		if (buflen < 0) {
+		if (buflen <= 0) {
 			numfullpathfail4++;
 			CACHE_RUNLOCK();
 			return (ENOMEM);
 		}
+		*--bp = '/';
+		buflen--;
 		slash_prefixed = 1;
 	}
 	while (vp != rdir && vp != rootvnode) {
@@ -1013,14 +1013,14 @@ vn_fullpath1(struct thread *td, struct v
 			if (error)
 				break;
 		}
-		*--bp = '/';
-		buflen--;
-		if (buflen < 0) {
+		if (buflen <= 0) {
 			numfullpathfail4++;
 			CACHE_RUNLOCK();
 			error = ENOMEM;
 			break;
 		}
+		*--bp = '/';
+		buflen--;
 		slash_prefixed = 1;
 	}
 	if (error)