linux-kernel - Re: Re: [BUG] ethernet:enic: A use after free bug in enic_hard_start

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Date:   Sat, 1 May 2021 23:34:21 +0800 (GMT+08:00)
From:   lyl2019@...l.ustc.edu.cn
To:     "Govindarajulu Varadarajan" <govind.varadar@...il.com>
Cc:     benve@...co.com, davem@...emloft.net, kuba@...nel.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: Re: [BUG] ethernet:enic: A use after free bug in
 enic_hard_start_xmit




> -----原始邮件-----
> 发件人: "Govindarajulu Varadarajan" <govind.varadar@...il.com>
> 发送时间: 2021-05-01 08:10:02 (星期六)
> 收件人: lyl2019@...l.ustc.edu.cn, benve@...co.com, davem@...emloft.net, kuba@...nel.org
> 抄送: netdev@...r.kernel.org, linux-kernel@...r.kernel.org
> 主题: Re: [BUG] ethernet:enic: A use after free bug in enic_hard_start_xmit
> 
> On Tue, 2021-04-27 at 10:55 +0800, lyl2019@...l.ustc.edu.cn wrote:
> > Hi, maintainers.
> >     Our code analyzer reported a uaf bug, but it is a little
> > difficult for me to fix it directly.
> > 
> > File: drivers/net/ethernet/cisco/enic/enic_main.c
> > In enic_hard_start_xmit, it calls enic_queue_wq_skb(). Inside
> > enic_queue_wq_skb, if some error happens, the skb will be freed
> > by dev_kfree_skb(skb). But the freed skb is still used in 
> > skb_tx_timestamp(skb).
> > 
> > ```
> >         enic_queue_wq_skb(enic, wq, skb);// skb could freed here
> > 
> >         if (vnic_wq_desc_avail(wq) < MAX_SKB_FRAGS + ENIC_DESC_MAX_SPLITS)
> >                 netif_tx_stop_queue(txq);
> >         skb_tx_timestamp(skb); // freed skb is used here.
> > ```
> > Bug introduced by fb7516d42478e ("enic: add sw timestamp support").
> 
> Thank you for reporting this.
> 
> One solution is to make enic_queue_wq_skb() return error and goto spin_unlock()
> incase of error.
> 
> Would you like to send the fix for this?
> 
> --
> Govind
> 

It is my pleasure, i have submitted this fix.
See https://lore.kernel.org/patchwork/patch/1420692/.

Thanks.