linux-kernel - Re: [PATCH] staging: ft1000: fix error path

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Date:	Sun, 26 Sep 2010 18:56:53 +0200
From:	Belisko Marek <marek.belisko@...il.com>
To:	Dan Carpenter <error27@...il.com>,
	Vasiliy Kulikov <segooon@...il.com>,
	kernel-janitors@...r.kernel.org,
	Greg Kroah-Hartman <gregkh@...e.de>,
	Marek Belisko <marek.belisko@...il.com>,
	devel@...verdev.osuosl.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] staging: ft1000: fix error path

On Sun, Sep 26, 2010 at 3:11 PM, Dan Carpenter <error27@...il.com> wrote:
> On Sun, Sep 26, 2010 at 12:59:55PM +0400, Vasiliy Kulikov wrote:
>> +err_free:
>> +     for (i--; i>=0; i--) {
>> +             kfree(pdpram_blk->pbuffer);
>> +             kfree(pdpram_blk);
>> +     }
>
> This is wrong.  I don't have linux-next so I can't see the context, why
> are we looping here?  The second iteration through the loop will cause a
> NULL dereference.
Some lines upper there is allocation of structure and it's internal
buffer in loop:
for (i=0; i<NUM_OF_FREE_BUFFERS; i++) {
    // Get memory for DPRAM_DATA link list
    pdpram_blk = kmalloc ( sizeof(DPRAM_BLK), GFP_KERNEL );
    // Get a block of memory to store command data
    pdpram_blk->pbuffer = kmalloc ( MAX_CMD_SQSIZE, GFP_KERNEL );
    // link provisioning data
    list_add_tail (&pdpram_blk->list, &freercvpool);
}

Free loop is correct in my opinion but kfree should be extended by checking
of NULL pointer because allocation of pdpram_blk could fail and we free also
pdpram_blk->pbuffer.
>
> Also there should be spaces before and after the ">=".
>
> regards,
> dan carpenter
>
>> +     return STATUS_FAILURE;
>>  }
>>
>
>

marek

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