Re: [PATCH 2/6] disk: part_efi: Add missing endianness conversions

On Mon, 3 Aug 2026 at 13:20, Ilias Apalodimas
<[email protected]> wrote:
>
> On Fri, 31 Jul 2026 at 15:40, Alexey Charkov <[email protected]> wrote:
> >
> > Several GPT header fields are read without converting from
> > little-endian, which is wrong on big-endian hosts.
>
> Probably because we got no BE architecture running EFI.

Isn't the EFI spec explicitly LE?

> > gpt_fill_pte() takes my_lba and partition_entry_lba raw when working out
> > the region a partition must not overlap, so on a big-endian host both
> > bounds are byte-swapped garbage and the overlap check does not do
> > anything useful.
> >
> > gpt_verify_partitions() compares the loop counter against
> > num_partition_entries raw, so its "More partitions than allowed!" guard
> > never triggers.
> >
> > It also swaps gpt_part_size, which is already in host order, having been
> > computed from two le64_to_cpu() results a few lines above. Drop the
> > conversion rather than adding one.
> >
> > All of this is a no-op on little-endian targets.
> >
> > Signed-off-by: Alexey Charkov <[email protected]>
>
> In any case it;'s good to have
> Reviewed-by: Ilias Apalodimas <[email protected]>
>
> > ---
> >  disk/part_efi.c | 8 ++++----
> >  1 file changed, 4 insertions(+), 4 deletions(-)
> >
> > diff --git a/disk/part_efi.c b/disk/part_efi.c
> > index af311867a285..062389c3af0c 100644
> > --- a/disk/part_efi.c
> > +++ b/disk/part_efi.c
> > @@ -462,10 +462,10 @@ int gpt_fill_pte(struct blk_desc *desc,
> >         char *str_type_guid;
> >         unsigned char *bin_type_guid;
> >  #endif
> > -       size_t hdr_start = gpt_h->my_lba;
> > +       size_t hdr_start = le64_to_cpu(gpt_h->my_lba);
> >         size_t hdr_end = hdr_start + 1;
> >
> > -       size_t pte_start = gpt_h->partition_entry_lba;
> > +       size_t pte_start = le64_to_cpu(gpt_h->partition_entry_lba);
> >         size_t pte_end = pte_start + gpt_pte_blocks(desc, gpt_h);
> >
> >         for (i = 0; i < parts; i++) {
> > @@ -851,7 +851,7 @@ int gpt_verify_partitions(struct blk_desc *desc,
> >         gpt_e = *gpt_pte;
> >
> >         for (i = 0; i < parts; i++) {
> > -               if (i == gpt_head->num_partition_entries) {
> > +               if (i == le32_to_cpu(gpt_head->num_partition_entries)) {
> >                         pr_err("More partitions than allowed!\n");
> >                         return -1;
> >                 }
> > @@ -877,7 +877,7 @@ int gpt_verify_partitions(struct blk_desc *desc,
> >                       (unsigned long long)gpt_part_size,
> >                       (unsigned long long)partitions[i].size);
> >
> > -               if (le64_to_cpu(gpt_part_size) != partitions[i].size) {
> > +               if (gpt_part_size != partitions[i].size) {
> >                         /* We do not check the extend partition size */
> >                         if ((i == parts - 1) && (partitions[i].size == 0))
> >                                 continue;
> >
> > --
> > 2.54.0
> >