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

On 7/31/26 14:40, Alexey Charkov wrote:
> Several GPT header fields are read without converting from
> little-endian, which is wrong on big-endian hosts.
> 
> 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]>

This change is not covered by the test in patch 6/6 as it runs only on 
the sandbox.

Please, ensure that the GPT tests are also executed on a big-endian 
systems, e.g malta64_defconfig which run in the CI via QEMU.

Reviewed-by: Heinrich Schuchardt <[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;
>