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gpt: fix partition table indexing and validation

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Portions of the code attempted to handle the fact that GPT entries on
disk may be larger than the currently defined struct while others
assumed the data could be indexed by the struct size directly. This
never came up because no utility uses a size larger than 128 bytes but
for the sake of safety we need to do this by the spec.
This commit is contained in:
Michael Marineau 2016-08-24 16:14:20 -07:00
parent 87dfbf34c4
commit bf127238ee
4 changed files with 176 additions and 12 deletions
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51
grub-core/lib/gpt.c
View file

@ -207,6 +207,13 @@ grub_gpt_pmbr_check (struct grub_msdos_partition_mbr *mbr)
return grub_error (GRUB_ERR_BAD_PART_TABLE, "invalid protective MBR");
}
static grub_uint64_t
grub_gpt_entries_size (struct grub_gpt_header *gpt)
{
return (grub_uint64_t) grub_le_to_cpu32 (gpt->maxpart) *
(grub_uint64_t) grub_le_to_cpu32 (gpt->partentry_size);
}
static grub_uint64_t
grub_gpt_entries_sectors (struct grub_gpt_header *gpt,
unsigned int log_sector_size)
@ -214,11 +221,16 @@ grub_gpt_entries_sectors (struct grub_gpt_header *gpt,
grub_uint64_t sector_bytes, entries_bytes;
sector_bytes = 1ULL << log_sector_size;
entries_bytes = (grub_uint64_t) grub_le_to_cpu32 (gpt->maxpart) *
(grub_uint64_t) grub_le_to_cpu32 (gpt->partentry_size);
entries_bytes = grub_gpt_entries_size (gpt);
return grub_divmod64(entries_bytes + sector_bytes - 1, sector_bytes, NULL);
}
static int
is_pow2 (grub_uint32_t n)
{
return (n & (n - 1)) == 0;
}
grub_err_t
grub_gpt_header_check (struct grub_gpt_header *gpt,
unsigned int log_sector_size)
@ -236,16 +248,23 @@ grub_gpt_header_check (struct grub_gpt_header *gpt,
if (gpt->crc32 != crc)
return grub_error (GRUB_ERR_BAD_PART_TABLE, "invalid GPT header crc32");
/* The header size must be between 92 and the sector size. */
/* The header size "must be greater than or equal to 92 and must be less
* than or equal to the logical block size." */
size = grub_le_to_cpu32 (gpt->headersize);
if (size < 92U || size > (1U << log_sector_size))
return grub_error (GRUB_ERR_BAD_PART_TABLE, "invalid GPT header size");
/* The partition entry size must be a multiple of 128. */
/* The partition entry size must be "a value of 128*(2^n) where n is an
* integer greater than or equal to zero (e.g., 128, 256, 512, etc.)." */
size = grub_le_to_cpu32 (gpt->partentry_size);
if (size < 128 || size % 128)
if (size < 128U || size % 128U || !is_pow2 (size / 128U))
return grub_error (GRUB_ERR_BAD_PART_TABLE, "invalid GPT entry size");
/* The minimum entries table size is specified in terms of bytes,
* regardless of how large the individual entry size is. */
if (grub_gpt_entries_size (gpt) < GRUB_GPT_DEFAULT_ENTRIES_SIZE)
return grub_error (GRUB_ERR_BAD_PART_TABLE, "invalid GPT entry table size");
/* And of course there better be some space for partitions! */
start = grub_le_to_cpu64 (gpt->start);
end = grub_le_to_cpu64 (gpt->end);
@ -411,7 +430,7 @@ static grub_err_t
grub_gpt_read_entries (grub_disk_t disk, grub_gpt_t gpt,
struct grub_gpt_header *header)
{
struct grub_gpt_partentry *entries = NULL;
void *entries = NULL;
grub_uint32_t count, size, crc;
grub_uint64_t sector;
grub_disk_addr_t addr;
@ -527,6 +546,26 @@ fail:
return NULL;
}
struct grub_gpt_partentry *
grub_gpt_get_partentry (grub_gpt_t gpt, grub_uint32_t n)
{
struct grub_gpt_header *header;
grub_size_t offset;
if (gpt->status & GRUB_GPT_PRIMARY_HEADER_VALID)
header = &gpt->primary;
else if (gpt->status & GRUB_GPT_BACKUP_HEADER_VALID)
header = &gpt->backup;
else
return NULL;
if (n >= grub_le_to_cpu32 (header->maxpart))
return NULL;
offset = (grub_size_t) grub_le_to_cpu32 (header->partentry_size) * n;
return (struct grub_gpt_partentry *) ((char *) gpt->entries + offset);
}
grub_err_t
grub_gpt_repair (grub_disk_t disk, grub_gpt_t gpt)
{