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SubjectRe: [PATCH 1/2] xen/xenbus: avoid large structs and arrays on the stack
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On 11.05.20 20:01, Boris Ostrovsky wrote:
> On 5/11/20 3:31 AM, Juergen Gross wrote:
>>
>> static int xenbus_map_ring_valloc_hvm(struct xenbus_device *dev,
>
>
> I wonder whether we can drop valloc/vfree from xenbus_ring_ops' names.

I can do that.

>
>
>> + struct map_ring_valloc *info,
>> grant_ref_t *gnt_ref,
>> unsigned int nr_grefs,
>> void **vaddr)
>> {
>> - struct xenbus_map_node *node;
>> + struct xenbus_map_node *node = info->node;
>> int err;
>> void *addr;
>> bool leaked = false;
>> - struct map_ring_valloc_hvm info = {
>> - .idx = 0,
>> - };
>> unsigned int nr_pages = XENBUS_PAGES(nr_grefs);
>>
>> - if (nr_grefs > XENBUS_MAX_RING_GRANTS)
>> - return -EINVAL;
>> -
>> - *vaddr = NULL;
>> -
>> - node = kzalloc(sizeof(*node), GFP_KERNEL);
>> - if (!node)
>> - return -ENOMEM;
>> -
>> err = alloc_xenballooned_pages(nr_pages, node->hvm.pages);
>> if (err)
>> goto out_err;
>>
>> gnttab_foreach_grant(node->hvm.pages, nr_grefs,
>> xenbus_map_ring_setup_grant_hvm,
>> - &info);
>> + info);
>>
>> err = __xenbus_map_ring(dev, gnt_ref, nr_grefs, node->handles,
>> - info.phys_addrs, GNTMAP_host_map, &leaked);
>> + info, GNTMAP_host_map, &leaked);
>> node->nr_handles = nr_grefs;
>>
>> if (err)
>> @@ -641,11 +654,13 @@ static int xenbus_map_ring_valloc_hvm(struct xenbus_device *dev,
>> spin_unlock(&xenbus_valloc_lock);
>>
>> *vaddr = addr;
>> + info->node = NULL;
>
>
> Is this so that xenbus_map_ring_valloc() doesn't free it accidentally?

Yes.


Juergen

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