netdev - Re: [PATCHv7 3/3] vhost_net: a kernel-level virtio server

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <878wema6o0.fsf@basil.nowhere.org>
Date:	Wed, 04 Nov 2009 12:08:47 +0100
From:	Andi Kleen <andi@...stfloor.org>
To:	"Michael S. Tsirkin" <mst@...hat.com>
Cc:	netdev@...r.kernel.org, virtualization@...ts.linux-foundation.org,
	kvm@...r.kernel.org, linux-kernel@...r.kernel.org, mingo@...e.hu,
	linux-mm@...ck.org, akpm@...ux-foundation.org
Subject: Re: [PATCHv7 3/3] vhost_net: a kernel-level virtio server

"Michael S. Tsirkin" <mst@...hat.com> writes:

Haven't really read the whole thing, just noticed something at a glance.

> +/* Expects to be always run from workqueue - which acts as
> + * read-size critical section for our kind of RCU. */
> +static void handle_tx(struct vhost_net *net)
> +{
> +	struct vhost_virtqueue *vq = &net->dev.vqs[VHOST_NET_VQ_TX];
> +	unsigned head, out, in, s;
> +	struct msghdr msg = {
> +		.msg_name = NULL,
> +		.msg_namelen = 0,
> +		.msg_control = NULL,
> +		.msg_controllen = 0,
> +		.msg_iov = vq->iov,
> +		.msg_flags = MSG_DONTWAIT,
> +	};
> +	size_t len, total_len = 0;
> +	int err, wmem;
> +	size_t hdr_size;
> +	struct socket *sock = rcu_dereference(vq->private_data);
> +	if (!sock)
> +		return;
> +
> +	wmem = atomic_read(&sock->sk->sk_wmem_alloc);
> +	if (wmem >= sock->sk->sk_sndbuf)
> +		return;
> +
> +	use_mm(net->dev.mm);

I haven't gone over all this code in detail, but that isolated reference count
use looks suspicious. What prevents the mm from going away before
you increment, if it's not the current one?

-Andi 

-- 
ak@...ux.intel.com -- Speaking for myself only.
--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html