On 17.09.19 03:07, Alastair D'Silva wrote:
> From: Alastair D'Silva <alastair@xxxxxxxxxxx>
>
> On PowerPC, the address ranges allocated to OpenCAPI LPC memory
> are allocated from firmware. These address ranges may be higher
> than what older kernels permit, as we increased the maximum
> permissable address in commit 4ffe713b7587
> ("powerpc/mm: Increase the max addressable memory to 2PB"). It is
> possible that the addressable range may change again in the
> future.
>
> In this scenario, we end up with a bogus section returned from
> __section_nr (see the discussion on the thread "mm: Trigger bug on
> if a section is not found in __section_nr").
>
> Adding a check here means that we fail early and have an
> opportunity to handle the error gracefully, rather than rumbling
> on and potentially accessing an incorrect section.
>
> Further discussion is also on the thread ("powerpc: Perform a bounds
> check in arch_add_memory").
>
> Signed-off-by: Alastair D'Silva <alastair@xxxxxxxxxxx>
> ---
> include/linux/memory_hotplug.h | 1 +
> mm/memory_hotplug.c | 13 ++++++++++++-
> 2 files changed, 13 insertions(+), 1 deletion(-)
>
> diff --git a/include/linux/memory_hotplug.h b/include/linux/memory_hotplug.h
> index f46ea71b4ffd..bc477e98a310 100644
> --- a/include/linux/memory_hotplug.h
> +++ b/include/linux/memory_hotplug.h
> @@ -110,6 +110,7 @@ extern void __online_page_increment_counters(struct page *page);
> extern void __online_page_free(struct page *page);
>
> extern int try_online_node(int nid);
> +int check_hotplug_memory_addressable(u64 start, u64 size);
>
> extern int arch_add_memory(int nid, u64 start, u64 size,
> struct mhp_restrictions *restrictions);
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index c73f09913165..02cb9a74f561 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -1030,6 +1030,17 @@ int try_online_node(int nid)
> return ret;
> }
>
> +int check_hotplug_memory_addressable(u64 start, u64 size)
> +{
> +#ifdef MAX_PHYSMEM_BITS
> + if ((start + size - 1) >> MAX_PHYSMEM_BITS)
> + return -E2BIG;
> +#endif
> +
> + return 0;
> +}
I guess checking for address space wrapping would be overkill. This
change makes sense for architecture-independent device drivers that make
use of the add/remove memory infrastructure (e.g., virtio-mem I am
working on).
Reviewed-by: David Hildenbrand <david@xxxxxxxxxx>
--
Thanks,
David / dhildenb
