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Subject[PATCH bpf-next] xsk: proper socket state check in xsk_poll
Date
From: Björn Töpel <bjorn.topel@intel.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@sina.com>
Reported-by: syzbot+c82697e3043781e08802@syzkaller.appspotmail.com
Fixes: 77cd0d7b3f25 ("xsk: add support for need_wakeup flag in AF_XDP rings")
Signed-off-by: Björn Töpel <bjorn.topel@intel.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
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