Re: [PATCH v3] efi: Ignore unrealistically large option roms

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On 29 April 2018 at 10:40, Hans de Goede <hdegoede@xxxxxxxxxx> wrote:
> Hi,
>
>
> On 29-04-18 09:43, Ingo Molnar wrote:
>>
>>
>> * Hans de Goede <hdegoede@xxxxxxxxxx> wrote:
>>
>>> diff --git a/arch/x86/boot/compressed/eboot.c
>>> b/arch/x86/boot/compressed/eboot.c
>>> index 47d3efff6805..8650ab268ee7 100644
>>> --- a/arch/x86/boot/compressed/eboot.c
>>> +++ b/arch/x86/boot/compressed/eboot.c
>>> @@ -122,7 +122,14 @@ __setup_efi_pci32(efi_pci_io_protocol_32 *pci,
>>> struct pci_setup_rom **__rom)
>>>         if (status != EFI_SUCCESS)
>>>                 return status;
>>>   -     if (!pci->romimage || !pci->romsize)
>>> +       /*
>>> +        * Some firmwares contain EFI function pointers at the place
>>> where the
>>> +        * romimage and romsize fields are supposed to be. Typically the
>>> EFI
>>> +        * code is mapped at high addresses, translating to an
>>> unrealistically
>>> +        * large romsize. The UEFI spec limits the size of option ROMs to
>>> 16
>>> +        * MiB so we reject any roms over 16 MiB in size to catch this.
>>> +        */
>>> +       if (!pci->romimage || !pci->romsize || pci->romsize > 0x1000000)
>>>                 return EFI_INVALID_PARAMETER;
>>>         size = pci->romsize + sizeof(*rom);
>>> @@ -230,7 +237,14 @@ __setup_efi_pci64(efi_pci_io_protocol_64 *pci,
>>> struct pci_setup_rom **__rom)
>>>         if (status != EFI_SUCCESS)
>>>                 return status;
>>>   -     if (!pci->romimage || !pci->romsize)
>>> +       /*
>>> +        * Some firmwares contain EFI function pointers at the place
>>> where the
>>> +        * romimage and romsize fields are supposed to be. Typically the
>>> EFI
>>> +        * code is mapped at high addresses, translating to an
>>> unrealistically
>>> +        * large romsize. The UEFI spec limits the size of option ROMs to
>>> 16
>>> +        * MiB so we reject any roms over 16 MiB in size to catch this.
>>> +        */
>>> +       if (!pci->romimage || !pci->romsize || pci->romsize > 0x1000000)
>>>                 return EFI_INVALID_PARAMETER;
>>
>>
>> Any reason why this couldn't be factored out into a efi_check_rom(pci)
>> kind of
>> helper function
>
>
> The pci pointer is of 2 different types:
>
> __setup_efi_pci32(efi_pci_io_protocol_32 *pci, ...
> __setup_efi_pci64(efi_pci_io_protocol_64 *pci, ...
>
> I guess I could give the helper a romimage and romsize argument to get
> around that.
> Ard, do you want me to do a v4 with such a helper ?
>

I think Lukas has a point, although I shouldn't expect you to implement that.

I will look into this myself, and rebase your patch on top of that.
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