From mboxrd@z Thu Jan 1 00:00:00 1970 From: Al Viro Subject: [PATCH 01/18] netlink: make the check for "send from tx_ring" deterministic Date: Sat, 31 Jan 2015 03:56:27 +0000 Message-ID: <1422676604-18533-1-git-send-email-viro@ZenIV.linux.org.uk> References: <20150131035513.GK29656@ZenIV.linux.org.uk> Cc: netdev@vger.kernel.org To: David Miller Return-path: Received: from zeniv.linux.org.uk ([195.92.253.2]:54981 "EHLO ZenIV.linux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755716AbbAaD4p (ORCPT ); Fri, 30 Jan 2015 22:56:45 -0500 In-Reply-To: <20150131035513.GK29656@ZenIV.linux.org.uk> Sender: netdev-owner@vger.kernel.org List-ID: From: Al Viro As it is, zero msg_iovlen means that the first iovec in the kernel array of iovecs is left uninitialized, so checking if its ->iov_base is NULL is random. Since the real users of that thing are doing sendto(fd, NULL, 0, ...), they are getting msg_iovlen = 1 and msg_iov[0] = {NULL, 0}, which is what this test is trying to catch. As suggested by davem, let's just check that msg_iovlen was 1 and msg_iov[0].iov_base was NULL - _that_ is well-defined and it catches what we want to catch. Signed-off-by: Al Viro --- net/netlink/af_netlink.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c index a36777b..af51d58 100644 --- a/net/netlink/af_netlink.c +++ b/net/netlink/af_netlink.c @@ -2298,7 +2298,11 @@ static int netlink_sendmsg(struct kiocb *kiocb, struct socket *sock, goto out; } + /* It's a really convoluted way for userland to ask for mmaped + * sendmsg(), but that's what we've got... */ if (netlink_tx_is_mmaped(sk) && + msg->msg_iter.type == ITER_IOVEC && + msg->msg_iter.nr_segs == 1 && msg->msg_iter.iov->iov_base == NULL) { err = netlink_mmap_sendmsg(sk, msg, dst_portid, dst_group, &scm); -- 2.1.4