[U-Boot] [PATCH] efi_loader: Fix crash on 32-bit systems

[Alexander Graf]

> On 13 Sep 2016, at 19:36, Robin Randhawa <robin.randhawa at arm.com> wrote:
> 
> A type mismatch in the efi_allocate_pool boot service flow causes
> hazardous memory scribbling on 32-bit systems.
> 
> This is efi_allocate_pool's prototype:
> 
> static efi_status_t EFIAPI efi_allocate_pool(int pool_type,
> 						    unsigned long size,
> 						    void **buffer);
> 
> Internally, it invokes efi_allocate_pages as follows:
> 
> efi_allocate_pages(0, pool_type, (size + 0xfff) >> 12,
> 					    (void*)buffer);
> 
> This is efi_allocate_pages' prototype:
> 
> efi_status_t efi_allocate_pages(int type, int memory_type,
> 					unsigned long pages,
> 					uint64_t *memory);
> 
> The problem: efi_allocate_pages does this internally:
> 
>    *memory = addr;
> 
> This fix in efi_allocate_pool uses a transitional uintptr_t cast to
> ensure the correct outcome, irrespective of the system's native word
> size.
> 
> This was observed when bootefi'ing the EFI instance of FreeBSD's first
> stage bootstrap (boot1.efi) on a 32-bit ARM platform (Qemu VExpress +
> Cortex-a9).
> 
> Signed-off-by: Robin Randhawa <robin.randhawa at arm.com>

Very nice catch!

> ---
> lib/efi_loader/efi_boottime.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/lib/efi_loader/efi_boottime.c b/lib/efi_loader/efi_boottime.c
> index be6f5e8..784891b 100644
> --- a/lib/efi_loader/efi_boottime.c
> +++ b/lib/efi_loader/efi_boottime.c
> @@ -134,9 +134,11 @@ static efi_status_t EFIAPI efi_allocate_pool(int pool_type, unsigned long size,
> 					     void **buffer)
> {
> 	efi_status_t r;
> +	efi_physical_addr_t t;
> 
> 	EFI_ENTRY("%d, %ld, %p", pool_type, size, buffer);
> -	r = efi_allocate_pages(0, pool_type, (size + 0xfff) >> 12, (void*)buffer);
> +	r = efi_allocate_pages(0, pool_type, (size + 0xfff) >> 12, &t);
> +	*buffer = (void *)(uintptr_t)t;

Can you please double-check that this is the only place the type mismatch happened? For this change however, the fix is already correct:

  Reviewed-by: Alexander Graf <agraf at suse.de>


Alex