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

commit 6d8d17499810479eabd10731179c04b2ca22152f upstream.

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>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/net/sunrpc/cache.c b/net/sunrpc/cache.c
index 72ad836..4530a91 100644 (file)
--- 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';