From: Yunsheng Lin <linyunsheng@huawei.com>
To: Ilias Apalodimas <ilias.apalodimas@linaro.org>, <netdev@vger.kernel.org>
Cc: Alexander Duyck <alexanderduyck@fb.com>,
"David S. Miller" <davem@davemloft.net>,
Jakub Kicinski <kuba@kernel.org>,
Alexander Lobakin <alobakin@pm.me>,
Jonathan Lemon <jonathan.lemon@gmail.com>,
Willem de Bruijn <willemb@google.com>,
Miaohe Lin <linmiaohe@huawei.com>,
Guillaume Nault <gnault@redhat.com>,
Cong Wang <cong.wang@bytedance.com>,
"Jesper Dangaard Brouer" <brouer@redhat.com>,
Matteo Croce <mcroce@microsoft.com>,
<linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 1/1 v2] skbuff: Fix a potential race while recycling page_pool packets
Date: Thu, 15 Jul 2021 12:00:57 +0800 [thread overview]
Message-ID: <bf326953-495f-db01-e554-42f4421d237a@huawei.com> (raw)
In-Reply-To: <20210709062943.101532-1-ilias.apalodimas@linaro.org>
On 2021/7/9 14:29, Ilias Apalodimas wrote:
> As Alexander points out, when we are trying to recycle a cloned/expanded
> SKB we might trigger a race. The recycling code relies on the
> pp_recycle bit to trigger, which we carry over to cloned SKBs.
> If that cloned SKB gets expanded or if we get references to the frags,
> call skbb_release_data() and overwrite skb->head, we are creating separate
> instances accessing the same page frags. Since the skb_release_data()
> will first try to recycle the frags, there's a potential race between
> the original and cloned SKB, since both will have the pp_recycle bit set.
>
> Fix this by explicitly those SKBs not recyclable.
> The atomic_sub_return effectively limits us to a single release case,
> and when we are calling skb_release_data we are also releasing the
> option to perform the recycling, or releasing the pages from the page pool.
>
> Fixes: 6a5bcd84e886 ("page_pool: Allow drivers to hint on SKB recycling")
> Reported-by: Alexander Duyck <alexanderduyck@fb.com>
> Suggested-by: Alexander Duyck <alexanderduyck@fb.com>
> Signed-off-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
> ---
> Changes since v1:
> - Set the recycle bit to 0 during skb_release_data instead of the
> individual fucntions triggering the issue, in order to catch all
> cases
> net/core/skbuff.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/net/core/skbuff.c b/net/core/skbuff.c
> index 12aabcda6db2..f91f09a824be 100644
> --- a/net/core/skbuff.c
> +++ b/net/core/skbuff.c
> @@ -663,7 +663,7 @@ static void skb_release_data(struct sk_buff *skb)
> if (skb->cloned &&
> atomic_sub_return(skb->nohdr ? (1 << SKB_DATAREF_SHIFT) + 1 : 1,
> &shinfo->dataref))
> - return;
> + goto exit;
Is it possible this patch may break the head frag page for the original skb,
supposing it's head frag page is from the page pool and below change clears
the pp_recycle for original skb, causing a page leaking for the page pool?
>
> skb_zcopy_clear(skb, true);
>
> @@ -674,6 +674,8 @@ static void skb_release_data(struct sk_buff *skb)
> kfree_skb_list(shinfo->frag_list);
>
> skb_free_head(skb);
> +exit:
> + skb->pp_recycle = 0;
> }
>
> /*
>
next prev parent reply other threads:[~2021-07-15 4:01 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-09 6:29 [PATCH 1/1 v2] skbuff: Fix a potential race while recycling page_pool packets Ilias Apalodimas
2021-07-09 14:34 ` Alexander Duyck
2021-07-09 17:29 ` Ilias Apalodimas
2021-07-12 11:52 ` Jesper Dangaard Brouer
2021-07-15 4:00 ` Yunsheng Lin [this message]
2021-07-15 10:00 ` Ilias Apalodimas
2021-07-15 10:38 ` Ilias Apalodimas
2021-07-15 10:47 ` Yunsheng Lin
2021-07-15 12:37 ` Ilias Apalodimas
2021-07-15 14:25 ` Alexander Duyck
2021-07-15 14:45 ` Ilias Apalodimas
2021-07-15 14:57 ` Alexander Duyck
2021-07-15 15:02 ` Ilias Apalodimas
2021-07-16 2:30 ` Yunsheng Lin
2021-07-16 6:43 ` Ilias Apalodimas
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