NFS: change sign of nfs_fh length

mainline inclusion
from mainline-4.20
commit 86bbd7422ae6a33735df6846fd685e46686da714
category: bugfix
bugzilla: 10365
CVE: NA

-------------------------------------------------

The filehandle has a length which is defined as a 32-bit
"unsigned integer".  Change sign of the length appropriately.
Signed-off-by: NFrank Sorenson <sorenson@redhat.com>
Signed-off-by: NTrond Myklebust <trond.myklebust@hammerspace.com>
Signed-off-by: NZhangXiaoxu <zhangxiaoxu5@huawei.com>
Reviewed-by: NHou Tao <houtao1@huawei.com>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>

fs/nfs/nfs4xdr.c

@@ -3516,7 +3516,7 @@ static int decode_attr_exclcreat_supported(struct xdr_stream *xdr,
 static int decode_attr_filehandle(struct xdr_stream *xdr, uint32_t *bitmap, struct nfs_fh *fh)
 {
 	__be32 *p;
-	int len;
+	u32 len;
 
 	if (fh != NULL)
 		memset(fh, 0, sizeof(*fh));