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

[Heinrich Schuchardt <xypron.glpk@gmx.de>]

Am 28. Juli 2023 03:51:55 MESZ schrieb Simon Glass <sjg@google.com>:
>Hi,
>
>On Thu, 27 Jul 2023 at 08:36, Dan Carpenter <dan.carpenter@linaro.org> wrote:
>>
>> 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.
>
>We should really use ulong for addresses and malloc() sizes.

Please, do not abuse long.

According to the C specification the size of long is independent of the size of pointers.

Addresses should be pointers and sizes should be size_t.

Best regards

Heinrich