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virtio_net: fix memory leak in XDP_REDIRECT 

XDP_REDIRECT calling xdp_do_redirect() can fail for multiple reasons
(which can be inspected by tracepoints). The current semantics is that
on failure the driver calling xdp_do_redirect() must handle freeing or
recycling the page associated with this frame.  This can be seen as an
optimization, as drivers usually have an optimized XDP_DROP code path
for frame recycling in place already.

The virtio_net driver didn't handle when xdp_do_redirect() failed.
This caused a memory leak as the page refcnt wasn't decremented on
failures.

The function __virtnet_xdp_xmit() did handle one type of failure,
when the xmit queue virtqueue_add_outbuf() is full, which "hides"
releasing a refcnt on the page.  Instead the function __virtnet_xdp_xmit()
must follow API of xdp_do_redirect(), which on errors leave it up to
the caller to free the page, of the failed send operation.

Fixes: 186b3c998c ("virtio-net: support XDP_REDIRECT")
Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Jesper Dangaard Brouer 2018-02-20 14:32:15 +01:00 committed by David S. Miller
parent 95dbe9e7b3
commit 11b7d897cc
1 changed files with 22 additions and 15 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

37
drivers/net/virtio_net.c
View File

@ -443,12 +443,8 @@ static bool __virtnet_xdp_xmit(struct virtnet_info *vi,
sg_init_one(sq->sg, xdp->data, xdp->data_end - xdp->data);
err = virtqueue_add_outbuf(sq->vq, sq->sg, 1, xdp->data, GFP_ATOMIC);
if (unlikely(err)) {
struct page *page = virt_to_head_page(xdp->data);
put_page(page);
return false;
}
if (unlikely(err))
return false; /* Caller handle free/refcnt */
return true;
}
@ -546,8 +542,11 @@ static struct sk_buff *receive_small(struct net_device *dev,
unsigned int buflen = SKB_DATA_ALIGN(GOOD_PACKET_LEN + headroom) +
SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
struct page *page = virt_to_head_page(buf);
unsigned int delta = 0, err;
unsigned int delta = 0;
struct page *xdp_page;
bool sent;
int err;
len -= vi->hdr_len;
rcu_read_lock();
@ -596,16 +595,19 @@ static struct sk_buff *receive_small(struct net_device *dev,
delta = orig_data - xdp.data;
break;
case XDP_TX:
if (unlikely(!__virtnet_xdp_xmit(vi, &xdp)))
sent = __virtnet_xdp_xmit(vi, &xdp);
if (unlikely(!sent)) {
trace_xdp_exception(vi->dev, xdp_prog, act);
else
*xdp_xmit = true;
goto err_xdp;
}
*xdp_xmit = true;
rcu_read_unlock();
goto xdp_xmit;
case XDP_REDIRECT:
err = xdp_do_redirect(dev, &xdp, xdp_prog);
if (!err)
*xdp_xmit = true;
if (err)
goto err_xdp;
*xdp_xmit = true;
rcu_read_unlock();
goto xdp_xmit;
default:
@ -677,6 +679,7 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
struct bpf_prog *xdp_prog;
unsigned int truesize;
unsigned int headroom = mergeable_ctx_to_headroom(ctx);
bool sent;
head_skb = NULL;
@ -745,10 +748,14 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
}
break;
case XDP_TX:
if (unlikely(!__virtnet_xdp_xmit(vi, &xdp)))
sent = __virtnet_xdp_xmit(vi, &xdp);
if (unlikely(!sent)) {
trace_xdp_exception(vi->dev, xdp_prog, act);
else
*xdp_xmit = true;
if (unlikely(xdp_page != page))
put_page(xdp_page);
goto err_xdp;
}
*xdp_xmit = true;
if (unlikely(xdp_page != page))
goto err_xdp;
rcu_read_unlock();