Re: [PATCH v2 1/2] EFI: avoid OOB config file reads

[Jan Beulich <jbeulich@xxxxxxxx>]

On 16.09.2026 16:37, George Dunlap wrote:
> On Wed, Mar 25, 2026 at 2:24 PM Jan Beulich <jbeulich@xxxxxxxx> wrote:
>> @@ -878,6 +882,23 @@ static bool __init read_section(const EF
>>
>>      file->ptr = ptr;
>>
>> +    /* For cfg file, if necessary allocate space to put an extra NUL there. 
>> */
>> +    if ( file == &cfg && file->size && !iscntrl(file->str[file->size - 1]) )
>> +    {
>> +        EFI_PHYSICAL_ADDRESS addr;
>> +        EFI_STATUS ret = efi_bs->AllocatePages(AllocateMaxAddress,
>> +                                               EfiLoaderData,
>> +                                               PFN_UP(file->size + 1), 
>> &addr);
> 
> efiapi.h lists the Memory parameter as OUT, but that seems to be a
> mistake; the UEFI spec [1] says this is IN OUT; and the other two
> callers of AllocatePages in Xen initialize the value before passing it
> in.  So we should probably fix both efiapi.h, and initialize this to
> an appropriate value, rather than passing in stack rubble.

Oh, yes, we definitely need to init the variable. I'm less certain about
efiapi.h, though, as that's an imported header. We'd need to check
gnuefi, and import a possible update from there. I guess I'll leave that
part to the maintainers...

Jan