[PATCH v2] efi_loader: Fix memory corruption on 32bit systems

[Dan Carpenter]

On Thu, Jul 27, 2023 at 11:22:15AM +0300, Ilias Apalodimas wrote:
> Hi Dan, 
> 
> [...]
> 
> > @@ -313,7 +313,7 @@ static int cmp_pe_section(const void *arg1, const void *arg2)
> >   *
> >   * Return:	valid pointer to a image, return NULL if allocation fails.
> >   */
> > -void *efi_prepare_aligned_image(void *efi, u64 *efi_size)
> > +void *efi_prepare_aligned_image(void *efi, size_t *efi_size)
> >  {
> >  	size_t new_efi_size;
> >  	void *new_efi;
> > @@ -600,7 +600,7 @@ static bool efi_image_authenticate(void *efi, size_t efi_size)
> >  	if (!efi_secure_boot_enabled())
> >  		return true;
> >  
> > -	new_efi = efi_prepare_aligned_image(efi, (u64 *)&efi_size);
> > +	new_efi = efi_prepare_aligned_image(efi, &efi_size);
> >  	if (!new_efi)
> >  		return false;
> >  
> > diff --git a/lib/efi_loader/efi_tcg2.c b/lib/efi_loader/efi_tcg2.c
> > index 49f8a5e77cbf..d57afd0c498b 100644
> > --- a/lib/efi_loader/efi_tcg2.c
> > +++ b/lib/efi_loader/efi_tcg2.c
> > @@ -882,7 +882,7 @@ out:
> >   *
> >   * Return:	status code
> >   */
> > -static efi_status_t tcg2_hash_pe_image(void *efi, u64 efi_size,
> > +static efi_status_t tcg2_hash_pe_image(void *efi, size_t efi_size,
> >  				       struct tpml_digest_values *digest_list)
> 
> Unfortunately the rabbit hole is a bit deeper with this one.
> tcg2_hash_pe_image() is called in 
> - tcg2_measure_pe_image(). This one is called in efi_load_pe() and the type
>   is indeed a size_t there, so that's fine
> - efi_tcg2_hash_log_extend_event(), this one is different...
> The function is described by the EFI spec [0] which mandates a u64... I
> think that was the reason efi_prepare_aligned_image() is using a u64 to
> begin with.  This one uses the size only though not the pointer, but in a
> 32bit platform it would truncate s size > UINT_MAX.
> 
> [0] https://trustedcomputinggroup.org/wp-content/uploads/EFI-Protocol-Specification-rev13-160330final.pdf

I have maybe misread something...  I don't think this is a real issue.
32bit systems aren't going to be able to allocate that much memory
anyway.  Also there are a lot of size_t parameters already so it's not
a new issue.

regards,
dan carpenter