nfs4: strengthen error check to avoid unexpected result

mainline inclusion
from mainline-v5.10-rc1
commit 82c596eb
category: bugfix
bugzilla: NA
CVE: NA

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

The variable error is ssize_t, which is signed and will
cast to unsigned when comapre with variable size, so add
a check to avoid unexpected result in case of negative
value of error.
Signed-off-by: NChengguang Xu <cgxu519@mykernel.net>
Signed-off-by: NAnna Schumaker <Anna.Schumaker@Netapp.com>
Signed-off-by: NZhang Xiaoxu <zhangxiaoxu5@huawei.com>
Reviewed-by: NZhang Yi <yi.zhang@huawei.com>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>

fs/nfs/nfs4proc.c

@@ -7246,7 +7246,7 @@ nfs4_listxattr_nfs4_label(struct inode *inode, char *list, size_t list_len)
 
 	if (nfs_server_capable(inode, NFS_CAP_SECURITY_LABEL)) {
 		len = security_inode_listsecurity(inode, list, list_len);
-		if (list_len && len > list_len)
+		if (len >= 0 && list_len && len > list_len)
 			return -ERANGE;
 	}
 	return len;