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Avoid to overwrite the loaded MBR partition table just because partition offset is 16

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This commit is contained in:
Thomas Schmitt 2022-04-23 09:17:08 +02:00
parent da8e3e66e7
commit 99251ade08
1 changed files with 54 additions and 9 deletions
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63
libisofs/system_area.c
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@ -1,6 +1,6 @@
/*
* Copyright (c) 2008 Vreixo Formoso
* Copyright (c) 2010 - 2019 Thomas Schmitt
* Copyright (c) 2010 - 2022 Thomas Schmitt
*
* This file is part of the libisofs project; you can redistribute it and/or
* modify it under the terms of the GNU General Public License version 2
@ -1881,6 +1881,56 @@ static void iso_dummy_mbr_partition(uint8_t *buf, int mode)
}
/* flag bit0= only accept partition 1 as match for partition_offset
*/
static
int iso_ensure_mbr_part_table(Ecma119Image *t, uint32_t img_blocks,
uint8_t *buf, int flag)
{
int part_type, ret, i, found_part = 0;
uint32_t start_lba, num_blocks;
/* Look for MBR partition which starts at t->opts->partition_offset * 4
and has non-zero length
*/
if (buf[510] == 0x55 && buf[511] == 0xaa &&
t->opts->partition_offset < 0x3fffffff && img_blocks < 0x3fffffff ) {
for (i = 0; i < 4; i++) {
start_lba = iso_read_lsb(buf + 446 + i * 16 + 8, 4);
num_blocks = iso_read_lsb(buf + 446 + i * 16 + 12, 4);
if (t->opts->partition_offset * 4 == start_lba && num_blocks > 0) {
found_part = i + 1;
break;
}
if (flag & 1)
break;
}
}
if (found_part > 0) {
/* Update size fields in found_part */
part_type = buf[446 + (found_part - 1) * 16 + 4];
if (t->opts->iso_mbr_part_type >= 0 &&
t->opts->iso_mbr_part_type <= 255)
part_type= t->opts->iso_mbr_part_type;
ret = write_mbr_partition_entry(found_part, part_type,
start_lba, img_blocks * 4,
t->partition_secs_per_head,
t->partition_heads_per_cyl, buf, 2);
} else {
part_type = 0xcd;
if (t->opts->iso_mbr_part_type >= 0 &&
t->opts->iso_mbr_part_type <= 255)
part_type= t->opts->iso_mbr_part_type;
ret = make_grub_msdos_label(img_blocks, t->partition_secs_per_head,
t->partition_heads_per_cyl,
(uint8_t) part_type, buf, 2);
}
if (ret != ISO_SUCCESS) /* error should never happen */
return ISO_ASSERT_FAILURE;
return ISO_SUCCESS;
}
/* @param flag
bit0= t->opts->ms_block is not counted in t->total_size
*/
@ -2085,14 +2135,9 @@ int iso_write_system_area(Ecma119Image *t, uint8_t *buf, int flag)
return ret;
} else if ((t->opts->partition_offset > 0 || will_append) &&
sa_type == 0 && t->mbr_req_count == 0) {
/* Write a simple partition table. */
part_type = 0xcd;
if (t->opts->iso_mbr_part_type >= 0 &&
t->opts->iso_mbr_part_type <= 255)
part_type= t->opts->iso_mbr_part_type;
ret = make_grub_msdos_label(img_blocks, t->partition_secs_per_head,
t->partition_heads_per_cyl,
(uint8_t) part_type, buf, 2);
ret= iso_ensure_mbr_part_table(t, img_blocks, buf,
((t->opts->appended_as_gpt && t->have_appended_partitions) ||
t->opts->partition_offset == 0));
if (ret != ISO_SUCCESS) /* error should never happen */
return ISO_ASSERT_FAILURE;
risk_of_ee = 1;