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Subject: Re: [PATCH] net: nvidia: forcedeth: Fix two possible concurrency
 use-after-free bugs
To:     Jia-Ju Bai <baijiaju1990@gmail.com>, davem@davemloft.net,
        keescook@chromium.org
Cc:     netdev@vger.kernel.org, linux-kernel@vger.kernel.org
References: <20190108124518.21986-1-baijiaju1990@gmail.com>
 <27392ae0-2c0f-f099-05d8-f9cdbfbd313e@oracle.com>
 <f9ab7ba3-573c-6703-1b01-37a9e0a9b769@gmail.com>
From:   Yanjun Zhu <yanjun.zhu@oracle.com>
Organization: Oracle Corporation
Message-ID: <f87bd4b7-81d5-1f0c-137e-ecbc02753257@oracle.com>
Date:   Wed, 9 Jan 2019 09:24:48 +0800
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On 2019/1/8 20:57, Jia-Ju Bai wrote:
>
>
> On 2019/1/8 20:54, Zhu Yanjun wrote:
>>
>> 在 2019/1/8 20:45, Jia-Ju Bai 写道:
>>> In drivers/net/ethernet/nvidia/forcedeth.c, the functions
>>> nv_start_xmit() and nv_start_xmit_optimized() can be concurrently
>>> executed with nv_poll_controller().
>>>
>>> nv_start_xmit
>>>    line 2321: prev_tx_ctx->skb = skb;
>>>
>>> nv_start_xmit_optimized
>>>    line 2479: prev_tx_ctx->skb = skb;
>>>
>>> nv_poll_controller
>>>    nv_do_nic_poll
>>>      line 4134: spin_lock(&np->lock);
>>>      nv_drain_rxtx
>>>        nv_drain_tx
>>>          nv_release_txskb
>>>            line 2004: dev_kfree_skb_any(tx_skb->skb);
>>>
>>> Thus, two possible concurrency use-after-free bugs may occur.
>>>
>>> To fix these possible bugs,
>>
>>
>> Does this really occur? Can you reproduce this ?
>
> This bug is not found by the real execution.
> It is found by a static tool written by myself, and then I check it by 
> manual code review.

Before "line 2004: dev_kfree_skb_any(tx_skb->skb); ",

"

                 nv_disable_irq(dev);
                 nv_napi_disable(dev);
                 netif_tx_lock_bh(dev);
                 netif_addr_lock(dev);
                 spin_lock(&np->lock);
                 /* stop engines */
                 nv_stop_rxtx(dev);   <---this stop rxtx
                 nv_txrx_reset(dev);
"

In this case, does nv_start_xmit or nv_start_xmit_optimized still work well?

Zhu Yanjun

>
>
> Best wishes,
> Jia-Ju Bai