Re: [Xen-devel] [PATCH] fix potential null dereference

[Julien Grall <julien.grall@xxxxxxxxxx>]

(CC the REST maintainers)

On 01/12/2018 11:40 PM, Stefano Stabellini wrote:
> handles can theoretically be NULL, check for it explicitly before
> dereferencing it.
I doubt handles could be NULL if LocateHandle succeed. This seems to be 
confirmed by the spec (Page 208 in UEFI spec 2.7).
So I am not entirely convince we should add yet another check in the 
code. An ASSERT might be better.
Cheers,

> CID: 1381838
> Signed-off-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>
>
> diff --git a/xen/common/efi/boot.c b/xen/common/efi/boot.c
> index 469bf98..431fe2e 100644
> --- a/xen/common/efi/boot.c
> +++ b/xen/common/efi/boot.c
> @@ -729,7 +729,7 @@ static EFI_GRAPHICS_OUTPUT_PROTOCOL __init 
> *efi_get_gop(void)
>       if ( !EFI_ERROR(status) )
>           status = efi_bs->LocateHandle(ByProtocol, &gop_guid, NULL, &size,
>                                         handles);
> -    if ( EFI_ERROR(status) )
> +    if ( EFI_ERROR(status) || handles == NULL )
>           size = 0;
>       for ( i = 0; i < size / sizeof(*handles); ++i )
>       {
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