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SubjectRe: [PATCH v4 3/4] efi: Fix efi_memmap_alloc() leaks
On 01/06/20 at 04:40pm, Dan Williams wrote:
> With efi_fake_memmap() and efi_arch_mem_reserve() the efi table may be
> updated and replaced multiple times. When that happens a previous
> dynamically allocated efi memory map can be garbage collected. Use the
> new EFI_MEMMAP_{SLAB,MEMBLOCK} flags to detect when a dynamically
> allocated memory map is being replaced.
>
> Debug statements in efi_memmap_free() reveal:
>
> efi: __efi_memmap_free:37: phys: 0x23ffdd580 size: 2688 flags: 0x2
> efi: __efi_memmap_free:37: phys: 0x9db00 size: 2640 flags: 0x2
> efi: __efi_memmap_free:37: phys: 0x9e580 size: 2640 flags: 0x2
>
> ...a savings of 7968 bytes on a qemu boot with 2 entries specified to
> efi_fake_mem=.
>
> Cc: Taku Izumi <izumi.taku@jp.fujitsu.com>
> Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> Signed-off-by: Dan Williams <dan.j.williams@intel.com>
> ---
> drivers/firmware/efi/memmap.c | 24 ++++++++++++++++++++++++
> 1 file changed, 24 insertions(+)
>
> diff --git a/drivers/firmware/efi/memmap.c b/drivers/firmware/efi/memmap.c
> index 04dfa56b994b..bffa320d2f9a 100644
> --- a/drivers/firmware/efi/memmap.c
> +++ b/drivers/firmware/efi/memmap.c
> @@ -29,6 +29,28 @@ static phys_addr_t __init __efi_memmap_alloc_late(unsigned long size)
> return PFN_PHYS(page_to_pfn(p));
> }
>
> +static void __init __efi_memmap_free(u64 phys, unsigned long size, unsigned long flags)
> +{
> + if (flags & EFI_MEMMAP_MEMBLOCK) {
> + if (slab_is_available())
> + memblock_free_late(phys, size);
> + else
> + memblock_free(phys, size);
> + } else if (flags & EFI_MEMMAP_SLAB) {
> + struct page *p = pfn_to_page(PHYS_PFN(phys));
> + unsigned int order = get_order(size);
> +
> + free_pages((unsigned long) page_address(p), order);
> + }
> +}
> +
> +static void __init efi_memmap_free(void)
> +{
> + __efi_memmap_free(efi.memmap.phys_map,
> + efi.memmap.desc_size * efi.memmap.nr_map,
> + efi.memmap.flags);
> +}
> +
> /**
> * efi_memmap_alloc - Allocate memory for the EFI memory map
> * @num_entries: Number of entries in the allocated map.
> @@ -100,6 +122,8 @@ static int __init __efi_memmap_init(struct efi_memory_map_data *data)
> return -ENOMEM;
> }
>
> + efi_memmap_free();
> +

This seems still not safe, see below function:
arch/x86/platform/efi/efi.c:
static void __init efi_clean_memmap(void)
It use same memmap for both old and new, and filter out those invalid
ranges in place, if the memory is freed then ..

> map.phys_map = data->phys_map;
> map.nr_map = data->size / data->desc_size;
> map.map_end = map.map + data->size;
>

Thanks
Dave

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