The start variable is only used inside a loop, and is never affected inside it, so it's a purely local variable.

In the same way the partition size is accessed several times, so we can store it in a variable.

Signed-off-by: Maxime Ripard maxime.ripard@free-electrons.com --- disk/part_efi.c | 14 ++++++++------ 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/disk/part_efi.c b/disk/part_efi.c index 75d0a78f0a1f..fa95ce12329a 100644 --- a/disk/part_efi.c +++ b/disk/part_efi.c @@ -432,7 +432,6 @@ int gpt_fill_pte(gpt_header *gpt_h, gpt_entry *gpt_e, disk_partition_t *partitions, int parts) { lbaint_t offset = (lbaint_t)le64_to_cpu(gpt_h->first_usable_lba); - lbaint_t start; lbaint_t last_usable_lba = (lbaint_t) le64_to_cpu(gpt_h->last_usable_lba); int i, k; @@ -448,24 +447,27 @@ int gpt_fill_pte(gpt_header *gpt_h, gpt_entry *gpt_e,

for (i = 0; i < parts; i++) { /* partition starting lba */ - start = partitions[i].start; + lbaint_t start = partitions[i].start; + lbaint_t size = partitions[i].size; + if (start && (start < offset)) { printf("Partition overlap\n"); return -1; } + if (start) { gpt_e[i].starting_lba = cpu_to_le64(start); - offset = start + partitions[i].size; + offset = start + size; } else { gpt_e[i].starting_lba = cpu_to_le64(offset); - offset += partitions[i].size; + offset += size; } if (offset > (last_usable_lba + 1)) { printf("Partitions layout exceds disk size\n"); return -1; } /* partition ending lba */ - if ((i == parts - 1) && (partitions[i].size == 0)) + if ((i == parts - 1) && (size == 0)) /* extend the last partition to maximuim */ gpt_e[i].ending_lba = gpt_h->last_usable_lba; else @@ -525,7 +527,7 @@ int gpt_fill_pte(gpt_header *gpt_h, gpt_entry *gpt_e, debug("%s: name: %s offset[%d]: 0x" LBAF " size[%d]: 0x" LBAF "\n", __func__, partitions[i].name, i, - offset, i, partitions[i].size); + offset, i, size); }

return 0;

The current code checks that no partitions overlap with the GPT partition table using the offset of the first LBA usable for that partition.

This works fine, unless you have a partition entry that is further away than it usually is and you want to create partitions in the gap between the GPT header and the GPT partition entries, for example to reflash a bootloader that needs to be set there.

Rework the test to something a bit smarter that checks whether a partition would overlap with either the GPT header or the partition entries, no matter where it is on the disk.

Partitions that do not have a start LBA specified will still start at the first LBA usable set in the GPT header, to avoid weird behaviours.

Signed-off-by: Maxime Ripard maxime.ripard@free-electrons.com --- disk/part_efi.c | 28 +++++++++++++++++++++------- 1 file changed, 21 insertions(+), 7 deletions(-)

diff --git a/disk/part_efi.c b/disk/part_efi.c index 807d01de39d0..2973d52f6abb 100644 --- a/disk/part_efi.c +++ b/disk/part_efi.c @@ -445,24 +445,38 @@ int gpt_fill_pte(struct blk_desc *dev_desc, char *str_type_guid; unsigned char *bin_type_guid; #endif + size_t hdr_start = gpt_h->my_lba; + size_t hdr_end = hdr_start + 1; + + size_t pte_start = gpt_h->partition_entry_lba; + size_t pte_end = pte_start + + gpt_h->num_partition_entries * gpt_h->sizeof_partition_entry / + dev_desc->blksz;

for (i = 0; i < parts; i++) { /* partition starting lba */ lbaint_t start = partitions[i].start; lbaint_t size = partitions[i].size;

- if (start && (start < offset)) { - printf("Partition overlap\n"); - return -1; - } - if (start) { - gpt_e[i].starting_lba = cpu_to_le64(start); offset = start + size; } else { - gpt_e[i].starting_lba = cpu_to_le64(offset); + start = offset; offset += size; } + + /* + * If our partition overlaps with either the GPT + * header, or the partition entry, reject it. + */ + if (((start <= hdr_end && hdr_start <= (start + size)) || + (start <= pte_end && pte_start <= (start + size)))) { + printf("Partition overlap\n"); + return -1; + } + + gpt_e[i].starting_lba = cpu_to_le64(start); + if (offset > (last_usable_lba + 1)) { printf("Partitions layout exceds disk size\n"); return -1;