==> Regarding Re: [patch] fix BUG: in fw_realloc_buffer; Andrew Morton <[email protected]> adds:
akpm> Jeff Moyer <[email protected]> wrote:
>>
>> Hi,
>>
>> The fw_realloc_buffer routine does not handle an increase in buffer size of
>> more than 4k. It's not clear to me why it expects that it will only get an
>> extra 4k of data. The attached patch modifies fw_realloc_buffer to vmalloc
>> as much memory as is requested, instead of what we previously had + 4k.
>>
>> I've tested this on my laptop, which would crash occaisionally on boot
>> without the patch. With the patch, it hasn't crashed, but I can't be
>> certain that this code path is exercised.
>>
>> Comments are very welcome.
>>
[snip]
akpm> A little bit neater this way, I think?
> --- devel/drivers/base/firmware_class.c~firmware-fix-bug-in-fw_realloc_buffer 2006-02-13 14:45:52.000000000 -0800
> +++ devel-akpm/drivers/base/firmware_class.c 2006-02-13 14:52:05.000000000 -0800
> @@ -211,18 +211,20 @@ static int
> fw_realloc_buffer(struct firmware_priv *fw_priv, int min_size)
> {
> u8 *new_data;
> + int new_size = fw_priv->alloc_size;
> if (min_size <= fw_priv->alloc_size)
> return 0;
> - new_data = vmalloc(fw_priv->alloc_size + PAGE_SIZE);
> + new_size = ALIGN(min_size, PAGE_SIZE);
> + new_data = vmalloc(new_size);
> if (!new_data) {
> printk(KERN_ERR "%s: unable to alloc buffer\n", __FUNCTION__);
> /* Make sure that we don't keep incomplete data */
> fw_load_abort(fw_priv);
> return -ENOMEM;
> }
> - fw_priv->alloc_size += PAGE_SIZE;
> + fw_priv->alloc_size = new_size;
> if (fw_priv->fw->data) {
> memcpy(new_data, fw_priv->fw->data, fw_priv->fw->size);
> vfree(fw_priv->fw->data);
> _
Well, I wasn't sure that you would only need to increase by a PAGE. If you
only need to account for page_size + alignment, then yes, this is better.
It simply wasn't clear to me that this is how we are called. If I'm not
mistaken, this is the write routine for a file in sysfs. If that is the
case, why should we assume that writes are broken up into PAGE_SIZE chunks?
Thanks,
Jeff
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