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SubjectRe: [PATCH] mm/hotplug: Verify hotplug memory range
On 08/09/2013 12:47 AM, Toshi Kani wrote:
> add_memory() and remove_memory() can only handle a memory range aligned
> with section. There are problems when an unaligned range is added and
> then deleted as follows:
>
> - add_memory() with an unaligned range succeeds, but __add_pages()
> called from add_memory() adds a whole section of pages even though
> a given memory range is less than the section size.
> - remove_memory() to the added unaligned range hits BUG_ON() in
> __remove_pages().
>
> This patch changes add_memory() and remove_memory() to check if a given
> memory range is aligned with section at the beginning. As the result,
> add_memory() fails with -EINVAL when a given range is unaligned, and
> does not add such memory range. This prevents remove_memory() to be
> called with an unaligned range as well. Note that remove_memory() has
> to use BUG_ON() since this function cannot fail.
>
> Signed-off-by: Toshi Kani<toshi.kani@hp.com>
> ---
> mm/memory_hotplug.c | 22 ++++++++++++++++++++++
> 1 file changed, 22 insertions(+)
>
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index ca1dd3a..ac182de 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -1069,6 +1069,22 @@ out:
> return ret;
> }
>
> +static int check_hotplug_memory_range(u64 start, u64 size)
> +{
> + u64 start_pfn = start>> PAGE_SHIFT;
> + u64 nr_pages = size>> PAGE_SHIFT;
> +
> + /* Memory range must be aligned with section */
> + if ((start_pfn& ~PAGE_SECTION_MASK) ||
> + (nr_pages % PAGES_PER_SECTION) || (!nr_pages)) {
> + pr_err("Unsupported hotplug range: start 0x%llx, size 0x%llx\n",
> + start, size);

I think the message here should tell users that only support range aligned
to section. Others seems OK to me.

Reviewed-by: Tang Chen <tangchen@cn.fujitsu.com>

Thanks.

> + return -EINVAL;
> + }
> +
> + return 0;
> +}
> +
> /* we are OK calling __meminit stuff here - we have CONFIG_MEMORY_HOTPLUG */
> int __ref add_memory(int nid, u64 start, u64 size)
> {
> @@ -1078,6 +1094,10 @@ int __ref add_memory(int nid, u64 start, u64 size)
> struct resource *res;
> int ret;
>
> + ret = check_hotplug_memory_range(start, size);
> + if (ret)
> + return ret;
> +
> lock_memory_hotplug();
>
> res = register_memory_resource(start, size);
> @@ -1786,6 +1806,8 @@ void __ref remove_memory(int nid, u64 start, u64 size)
> {
> int ret;
>
> + BUG_ON(check_hotplug_memory_range(start, size));
> +
> lock_memory_hotplug();
>
> /*
>


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