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mbr: Added assertions for overlapping partitions #6700

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Apr 30, 2018
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mbr: Added assertions for overlapping partitions #6700

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14 changes: 14 additions & 0 deletions features/filesystem/bd/MBRBlockDevice.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -96,6 +96,7 @@ static int partition_absolute(
table->entries[part-1].type = type;

// lba dimensions
MBED_ASSERT(bd->is_valid_erase(offset, size));
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Wondering... shouldn't the assert work on LBA? if yes, it should be moved to L103 MBED_ASSERT(bd->is_valid_erase(lba_offset, lba_size));

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Ah, lba_offset and lba_size is in units of erase blocks. The offset and size are in units of bytes. bd->is_valid_erase operates in units of bytes.

We could also have an assert on lba_offset and lba_size but I thought it would be redundant. Do you think we should have that as well?

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No, don't bother.

uint32_t sector = std::max<uint32_t>(bd->get_erase_size(), 512);
uint32_t lba_offset = offset / sector;
uint32_t lba_size = size / sector;
Expand All @@ -106,6 +107,19 @@ static int partition_absolute(
tochs(lba_offset, table->entries[part-1].chs_start);
tochs(lba_offset+lba_size-1, table->entries[part-1].chs_stop);

// Check that we don't overlap other entries
for (int i = 1; i <= 4; i++) {
if (i != part && table->entries[i-1].type != 0x00) {
uint32_t neighbor_lba_offset = fromle32(table->entries[i-1].lba_offset);
uint32_t neighbor_lba_size = fromle32(table->entries[i-1].lba_size);
MBED_ASSERT(
(lba_offset >= neighbor_lba_offset + neighbor_lba_size) ||
(lba_offset + lba_size <= neighbor_lba_offset));
(void)neighbor_lba_offset;
(void)neighbor_lba_size;
}
}

// Write out MBR
err = bd->erase(0, bd->get_erase_size());
if (err) {
Expand Down