From c8b4c76eed87a28addbdc90f84635dd414796b51 Mon Sep 17 00:00:00 2001
From: kib <kib@FreeBSD.org>
Date: Fri, 20 Mar 2009 11:08:57 +0000
Subject: [PATCH] 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
---
 sys/kern/vfs_cache.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/sys/kern/vfs_cache.c b/sys/kern/vfs_cache.c
index f114c187bde6..0d506bc8e68e 100644
--- a/sys/kern/vfs_cache.c
+++ b/sys/kern/vfs_cache.c
@@ -970,13 +970,13 @@ vn_fullpath1(struct thread *td, struct vnode *vp, struct vnode *rdir,
 			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 vnode *vp, struct vnode *rdir,
 			if (error)
 				break;
 		}
-		*--bp = '/';
-		buflen--;
-		if (buflen < 0) {
+		if (buflen <= 0) {
 			numfullpathfail4++;
 			CACHE_RUNLOCK();
 			error = ENOMEM;
 			break;
 		}
+		*--bp = '/';
+		buflen--;
 		slash_prefixed = 1;
 	}
 	if (error)