[PATCH] fs: Fix link_path_walk to return -ENOENT on empty path

[Jules Maselbas]

link_path_walk was returning 0 when passed with an empty path,
this lead calling code to assume that the struct nameidata nd
is valid and thus has a `last` field populated, which is not.
In the end causing a runtime crash.

This issue can easily be reproduced by running the command:
cat ""

Reported-by: Neeraj Pal <neerajpal09 at gmail.com>
Signed-off-by: Jules Maselbas <jmaselbas at kalray.eu>
---
 fs/fs.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/fs/fs.c b/fs/fs.c
index a02332491..6de5a3b59 100644
--- a/fs/fs.c
+++ b/fs/fs.c
@@ -1928,6 +1928,8 @@ static int link_path_walk(const char *name, struct nameidata *nd)
 	int err;
 	char separator = '/';
 
+	if (!*name)
+		return -ENOENT;
 	while (*name=='/')
 		name++;
 	if (!*name)
-- 
2.17.1