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Subject: Re: [PATCH] net: nvidia: forcedeth: Fix two possible concurrency
 use-after-free bugs
To:     Zhu Yanjun <yanjun.zhu@oracle.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>
From:   Jia-Ju Bai <baijiaju1990@gmail.com>
Message-ID: <f9ab7ba3-573c-6703-1b01-37a9e0a9b769@gmail.com>
Date:   Tue, 8 Jan 2019 20:57:14 +0800
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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.


Best wishes,
Jia-Ju Bai