netdev - [PATCH bpf-next] xsk: proper socket state check in xsk

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Message-Id: <20190820100405.25564-1-bjorn.topel@gmail.com>
Date:   Tue, 20 Aug 2019 12:04:05 +0200
From:   Björn Töpel <bjorn.topel@...il.com>
To:     syzbot+c82697e3043781e08802@...kaller.appspotmail.com,
        ast@...nel.org, daniel@...earbox.net, netdev@...r.kernel.org
Cc:     bjorn.topel@...el.com, bpf@...r.kernel.org, davem@...emloft.net,
        hawk@...nel.org, jakub.kicinski@...ronome.com,
        john.fastabend@...il.com, jonathan.lemon@...il.com, kafai@...com,
        linux-kernel@...r.kernel.org, magnus.karlsson@...el.com,
        songliubraving@...com, syzkaller-bugs@...glegroups.com,
        xdp-newbies@...r.kernel.org, yhs@...com, hdanton@...a.com
Subject: [PATCH bpf-next] xsk: proper socket state check in xsk_poll

From: Björn Töpel <bjorn.topel@...el.com>

The poll() implementation for AF_XDP sockets did not perform the
proper state checks, prior accessing the socket umem. This patch fixes
that by performing a xsk_is_bound() check.

Suggested-by: Hillf Danton <hdanton@...a.com>
Reported-by: syzbot+c82697e3043781e08802@...kaller.appspotmail.com
Fixes: 77cd0d7b3f25 ("xsk: add support for need_wakeup flag in AF_XDP rings")
Signed-off-by: Björn Töpel <bjorn.topel@...el.com>
---
 net/xdp/xsk.c | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c
index ee4428a892fa..08bed5e92af4 100644
--- a/net/xdp/xsk.c
+++ b/net/xdp/xsk.c
@@ -356,13 +356,20 @@ static int xsk_generic_xmit(struct sock *sk, struct msghdr *m,
 	return err;
 }
 
+static bool xsk_is_bound(struct xdp_sock *xs)
+{
+	struct net_device *dev = READ_ONCE(xs->dev);
+
+	return dev && xs->state == XSK_BOUND;
+}
+
 static int xsk_sendmsg(struct socket *sock, struct msghdr *m, size_t total_len)
 {
 	bool need_wait = !(m->msg_flags & MSG_DONTWAIT);
 	struct sock *sk = sock->sk;
 	struct xdp_sock *xs = xdp_sk(sk);
 
-	if (unlikely(!xs->dev))
+	if (unlikely(!xsk_is_bound(xs)))
 		return -ENXIO;
 	if (unlikely(!(xs->dev->flags & IFF_UP)))
 		return -ENETDOWN;
@@ -383,6 +390,9 @@ static unsigned int xsk_poll(struct file *file, struct socket *sock,
 	struct net_device *dev = xs->dev;
 	struct xdp_umem *umem = xs->umem;
 
+	if (unlikely(!xsk_is_bound(xs)))
+		return mask;
+
 	if (umem->need_wakeup)
 		dev->netdev_ops->ndo_xsk_wakeup(dev, xs->queue_id,
 						umem->need_wakeup);
@@ -417,7 +427,7 @@ static void xsk_unbind_dev(struct xdp_sock *xs)
 {
 	struct net_device *dev = xs->dev;
 
-	if (!dev || xs->state != XSK_BOUND)
+	if (!xsk_is_bound(xs))
 		return;
 
 	xs->state = XSK_UNBOUND;
-- 
2.20.1