[PATCH 3.12 10/50] __dentry_path() fixes

[Jiri Slaby]

From: Al Viro <viro@xxxxxxxxxxxxxxxxxx>

3.12-stable review patch.  If anyone has any objections, please let me know.

===============

commit f6500801522c61782d4990fa1ad96154cb397cd4 upstream.

* we need to save the starting point for restarts
* reject pathologically short buffers outright

Spotted-by: Denys Vlasenko <dvlasenk@xxxxxxxxxx>
Spotted-by: Oleg Nesterov <oleg@xxxxxxxxxx>
Signed-off-by: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Jiri Slaby <jslaby@xxxxxxx>
---
 fs/dcache.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/fs/dcache.c b/fs/dcache.c
index 008f524e195a..8ef74f3d8fe5 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -3122,19 +3122,22 @@ char *simple_dname(struct dentry *dentry, char *buffer, int buflen)
 /*
  * Write full pathname from the root of the filesystem into the buffer.
  */
-static char *__dentry_path(struct dentry *dentry, char *buf, int buflen)
+static char *__dentry_path(struct dentry *d, char *buf, int buflen)
 {
+	struct dentry *dentry;
 	char *end, *retval;
 	int len, seq = 0;
 	int error = 0;
 
+	if (buflen < 2)
+		goto Elong;
+
 	rcu_read_lock();
 restart:
+	dentry = d;
 	end = buf + buflen;
 	len = buflen;
 	prepend(&end, &len, "\0", 1);
-	if (buflen < 1)
-		goto Elong;
 	/* Get '/' right */
 	retval = end-1;
 	*retval = '/';
-- 
1.9.2

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