Messages in this thread | | | Date | Mon, 16 Sep 2019 21:47:07 +0200 (CEST) | Subject | Re: [PATCH 1/1] xen-netfront: do not assume sk_buff_head list is empty in error handling | From | David Miller <> |
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From: Dongli Zhang <dongli.zhang@oracle.com> Date: Mon, 16 Sep 2019 11:46:59 +0800
> When skb_shinfo(skb) is not able to cache extra fragment (that is, > skb_shinfo(skb)->nr_frags >= MAX_SKB_FRAGS), xennet_fill_frags() assumes > the sk_buff_head list is already empty. As a result, cons is increased only > by 1 and returns to error handling path in xennet_poll(). > > However, if the sk_buff_head list is not empty, queue->rx.rsp_cons may be > set incorrectly. That is, queue->rx.rsp_cons would point to the rx ring > buffer entries whose queue->rx_skbs[i] and queue->grant_rx_ref[i] are > already cleared to NULL. This leads to NULL pointer access in the next > iteration to process rx ring buffer entries. > > Below is how xennet_poll() does error handling. All remaining entries in > tmpq are accounted to queue->rx.rsp_cons without assuming how many > outstanding skbs are remained in the list. > > 985 static int xennet_poll(struct napi_struct *napi, int budget) > ... ... > 1032 if (unlikely(xennet_set_skb_gso(skb, gso))) { > 1033 __skb_queue_head(&tmpq, skb); > 1034 queue->rx.rsp_cons += skb_queue_len(&tmpq); > 1035 goto err; > 1036 } > > It is better to always have the error handling in the same way. > > Fixes: ad4f15dc2c70 ("xen/netfront: don't bug in case of too many frags") > Signed-off-by: Dongli Zhang <dongli.zhang@oracle.com>
Applied and queued up for -stable.
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