linux-kernel - Re: [PATCH v2] staging: vt6655: check for memory allocation failures

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Date:   Thu, 29 Mar 2018 19:53:25 +0900
From:   ji-hun Kim <jihuun.k@...il.com>
To:     Jia-Ju Bai <baijiaju1990@...il.com>
Cc:     Ji-Hun Kim <ji_hun.kim@...sung.com>, gregkh@...uxfoundation.org,
        forest@...ttletooquiet.net, dartnorris@...il.com,
        santhameena13@...il.com, julia.lawall@...6.fr, y.k.oh@...sung.com,
        devel@...verdev.osuosl.org, linux-kernel@...r.kernel.org,
        kernel-janitors@...r.kernel.org
Subject: Re: [PATCH v2] staging: vt6655: check for memory allocation failures

2018-03-29 17:00 GMT+09:00 Jia-Ju Bai <baijiaju1990@...il.com>:
>
>
>
> On 2018/3/29 15:22, Ji-Hun Kim wrote:
>>
>> There are no null pointer checking on rd_info and td_info values which
>> are allocated by kzalloc. It has potential null pointer dereferencing
>> issues. Add return when allocation is failed.
>>
>> Signed-off-by: Ji-Hun Kim <ji_hun.kim@...sung.com>
>> ---
>>
>> Change: since v1:
>>
>> - Delete WARN_ON which can makes crashes on some machines.
>> - Instead of return directly, goto freeing function for freeing previously
>>    allocated memory in the for loop after kzalloc() failed.
>> - In the freeing function, if td_info and rd_info are not allocated, no
>>    needs to free.
>>
>>   drivers/staging/vt6655/device_main.c | 64 +++++++++++++++++++++++++-----------
>>   1 file changed, 44 insertions(+), 20 deletions(-)
>>
>> diff --git a/drivers/staging/vt6655/device_main.c b/drivers/staging/vt6655/device_main.c
>> index fbc4bc6..ecbba43 100644
>> --- a/drivers/staging/vt6655/device_main.c
>> +++ b/drivers/staging/vt6655/device_main.c
>> @@ -539,7 +539,8 @@ static void device_init_rd0_ring(struct vnt_private *priv)
>>              i ++, curr += sizeof(struct vnt_rx_desc)) {
>>                 desc = &priv->aRD0Ring[i];
>>                 desc->rd_info = kzalloc(sizeof(*desc->rd_info), GFP_KERNEL);
>> -
>> +               if (!desc->rd_info)
>> +                       goto error;
>>                 if (!device_alloc_rx_buf(priv, desc))
>>                         dev_err(&priv->pcid->dev, "can not alloc rx bufs\n");
>>   @@ -550,6 +551,10 @@ static void device_init_rd0_ring(struct vnt_private *priv)
>>         if (i > 0)
>>                 priv->aRD0Ring[i-1].next_desc = cpu_to_le32(priv->rd0_pool_dma);
>>         priv->pCurrRD[0] = &priv->aRD0Ring[0];
>> +
>> +       return;
>> +error:
>> +       device_free_rd0_ring(priv);
>>   }
>>
>
>
> I think you should return an error number here, because device_init_rd0_ring() is called by vnt_start().
> You should also implement error handling code in vnt_start(), and let vnt_start() returns an error number too.
> The same for device_init_rd1_ring(), device_init_td0_ring() and device_init_td1_ring().
>

Hi Jia-Ju, Thanks for the feedback. All right, those function looks
that needs returns
an error number. I will implement error handling code and send a patch
v3 tomorrow

Best regards,
Ji-Hun