Re: [PATCH] drivers/mmc/card/block.c: fix potential null dereference 'idata'

[Andy Shevchenko]

On Mon, May 9, 2011 at 6:05 PM, Vladimir Motyka
<vladimir.motyka@xxxxxxxxx> wrote:
> On 05/09/2011 04:32 PM, Julia Lawall wrote:
>> On Mon, 9 May 2011, Vladimir Motyka wrote:
>>
>>> When allocation of idata fails there was a null dereferece.
>>
>> Why not have a different label for the two cases? ÂThat would make the
>> code easier to statically analyze, and perhaps be more understandable as
>> well.
>>
>> julia
>>
> I think You are right. So it could be better like this?
>
> diff --git a/drivers/mmc/card/block.c b/drivers/mmc/card/block.c
> index 3dec493..a03cdc6 100644
> --- a/drivers/mmc/card/block.c
> +++ b/drivers/mmc/card/block.c
> @@ -237,7 +237,7 @@ static struct mmc_blk_ioc_data
> *mmc_blk_ioctl_copy_from_user(
> Â Â Â Âidata = kzalloc(sizeof(*idata), GFP_KERNEL);
> Â Â Â Âif (!idata) {
> Â Â Â Â Â Â Â Âerr = -ENOMEM;
> - Â Â Â Â Â Â Â goto copy_err;
> + Â Â Â Â Â Â Â goto alloc_err;
> Â Â Â Â}
>
> Â Â Â Âif (copy_from_user(&idata->ic, user, sizeof(idata->ic))) {
> @@ -266,9 +266,9 @@ static struct mmc_blk_ioc_data
> *mmc_blk_ioctl_copy_from_user(
> Â Â Â Âreturn idata;
>
> Âcopy_err:
> - Â Â Â if(idata)
> - Â Â Â Â Â Â Â kfree(idata->buf);
> + Â Â Â kfree(idata->buf);
Make it one patch not series.

> Â Â Â Âkfree(idata);
> +alloc_err:
> Â Â Â Âreturn ERR_PTR(err);
> Â}
>
> Or it could return right after allocation fails so there needn't be
> goto. It is simplier, but maybe worse looking and to read. What is your
> opinion?
>
> Vladimir Motyka
>
>>
>>> Signed-off-by: Vladimir Motyka <vladimir.motyka@xxxxxxxxx>
>>>
>>> ---
>>> diff --git a/drivers/mmc/card/block.c b/drivers/mmc/card/block.c
>>> index 407836d..3dec493 100644
>>> --- a/drivers/mmc/card/block.c
>>> +++ b/drivers/mmc/card/block.c
>>> @@ -266,10 +266,10 @@ static struct mmc_blk_ioc_data
>>> *mmc_blk_ioctl_copy_from_user(
>>> Â Â Âreturn idata;
>>>
>>> Âcopy_err:
>>> - Â Âkfree(idata->buf);
>>> + Â Âif(idata)
>>> + Â Â Â Â Â Âkfree(idata->buf);
>>> Â Â Âkfree(idata);
>>> Â Â Âreturn ERR_PTR(err);
>>> -
>>> Â}
>>>
>>> Âstatic int mmc_blk_ioctl_cmd(struct block_device *bdev,
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-- 
With Best Regards,
Andy Shevchenko
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