Re: [PATCH v2 3/4] efi: Fix efi_memmap_alloc() leaks

[Dave Young]

Hi Dan,
On 12/31/19 at 02:04pm, 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.
> 
> Cc: Taku Izumi <izumi.taku@xxxxxxxxxxxxxx>
> Cc: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>
> Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>
> ---
>  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 2b81ee6858a9..188ab3cd5c52 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 (WARN_ON(slab_is_available() && (flags & EFI_MEMMAP_MEMBLOCK)))
> +		return;
> +
> +	if (flags & EFI_MEMMAP_MEMBLOCK) {
> +		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.
> @@ -209,6 +231,8 @@ int __init efi_memmap_install(phys_addr_t addr, unsigned int nr_map,
>  	data.desc_size = efi.memmap.desc_size;
>  	flags |= efi.memmap.flags & EFI_MEMMAP_LATE;
>  
> +	efi_memmap_free();
> +
>  	return __efi_memmap_init(&data, flags);

Hmm, only free the memmap in case __efi_memmap_init succeeded..

Thanks
Dave