[PATCH] dcache: error out if the name buffer is too short

[Denys Vlasenko <dvlasenk@redhat.com>]

This change makes __dentry_path() and d_path()
immediately return ENAMETOOLONG if buflen < 2.

Cc: Jan Kratochvil <jan.kratochvil@redhat.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com>
---
 fs/dcache.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/fs/dcache.c b/fs/dcache.c
index cb4a106..2fba276 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -3055,6 +3055,9 @@ char *d_path(const struct path *path, char *buf, int buflen)
 	struct path root;
 	int error;
 
+	if (buflen < 2)
+		return ERR_PTR(-ENAMETOOLONG);
+
 	/*
 	 * We have various synthetic filesystems that never get mounted.  On
 	 * these filesystems dentries are never used for lookup purposes, and
@@ -3122,13 +3125,14 @@ static char *__dentry_path(struct dentry *dentry, char *buf, int buflen)
 	int len, seq = 0;
 	int error = 0;
 
+	if (buflen < 2)
+		goto Elong;
+
 	rcu_read_lock();
 restart:
 	end = buf + buflen;
 	len = buflen;
 	prepend(&end, &len, "\0", 1);
-	if (buflen < 1)
-		goto Elong;
 	/* Get '/' right */
 	retval = end-1;
 	*retval = '/';
-- 
1.8.1.4