nfsd: don't allow zero length strings in cache_parse()

There is no point in passing a zero length string here and quite a
few of that cache_parse() implementations will Oops if count is
zero.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Cc: stable@kernel.org
Signed-off-by: J. Bruce Fields <bfields@redhat.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/net/sunrpc/cache.c b/net/sunrpc/cache.c
index 465df9ae1046..8c6598e0334a 100644
--- a/net/sunrpc/cache.c
+++ b/net/sunrpc/cache.c
@@ -828,6 +828,8 @@ static ssize_t cache_do_downcall(char *kaddr, const char __user *buf,
 {
         ssize_t ret;
 
+        if (count == 0)
+                return -EINVAL;
         if (copy_from_user(kaddr, buf, count))
                 return -EFAULT;
         kaddr[count] = '\0';