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| author | Rafał Miłecki <rafal@milecki.pl> | 2018-04-12 08:24:52 +0300 |
|---|---|---|
| committer | Boris Brezillon <boris.brezillon@bootlin.com> | 2018-05-12 10:42:38 +0300 |
| commit | 237ea0d4762cc14d0fc80e80d61f0f08e1050c7f (patch) | |
| tree | a75c119297bc01792bfe9ecee94bc2c9be4e560f /drivers/mtd/bcm47xxpart.c | |
| parent | 5ac67ce36cfe38b4c104a42ce52c5c8d526f1c95 (diff) | |
| download | linux-237ea0d4762cc14d0fc80e80d61f0f08e1050c7f.tar.xz | |
mtd: bcm47xxpart: improve handling TRX partition size
When bcm47xxpart finds a TRX partition (container) it's supposed to jump
to the end of it and keep looking for more partitions. TRX and its
subpartitions are handled by a separate parser.
The problem with old code was relying on the length specified in a TRX
header. That isn't reliable as TRX is commonly modified to have checksum
cover only non-changing subpartitions. Otherwise modifying e.g. a rootfs
would result in CRC32 mismatch and bootloader refusing to boot a
firmware.
Fix it by trying better to figure out a real TRX size. We can securely
assume that TRX has to cover all subpartitions and the last one is at
least of a block size in size. Then compare it with a length field.
This makes code more optimal & reliable thanks to skipping data that
shouldn't be parsed.
Signed-off-by: Rafał Miłecki <rafal@milecki.pl>
Signed-off-by: Boris Brezillon <boris.brezillon@bootlin.com>
Diffstat (limited to 'drivers/mtd/bcm47xxpart.c')
| -rw-r--r-- | drivers/mtd/bcm47xxpart.c | 22 |
1 files changed, 18 insertions, 4 deletions
diff --git a/drivers/mtd/bcm47xxpart.c b/drivers/mtd/bcm47xxpart.c index fe2581d9d882..1f0239848ebe 100644 --- a/drivers/mtd/bcm47xxpart.c +++ b/drivers/mtd/bcm47xxpart.c @@ -186,6 +186,8 @@ static int bcm47xxpart_parse(struct mtd_info *master, /* TRX */ if (buf[0x000 / 4] == TRX_MAGIC) { struct trx_header *trx; + uint32_t last_subpart; + uint32_t trx_size; if (trx_num >= ARRAY_SIZE(trx_parts)) pr_warn("No enough space to store another TRX found at 0x%X\n", @@ -195,11 +197,23 @@ static int bcm47xxpart_parse(struct mtd_info *master, bcm47xxpart_add_part(&parts[curr_part++], "firmware", offset, 0); - /* Jump to the end of TRX */ + /* + * Try to find TRX size. The "length" field isn't fully + * reliable as it could be decreased to make CRC32 cover + * only part of TRX data. It's commonly used as checksum + * can't cover e.g. ever-changing rootfs partition. + * Use offsets as helpers for assuming min TRX size. + */ trx = (struct trx_header *)buf; - offset = roundup(offset + trx->length, blocksize); - /* Next loop iteration will increase the offset */ - offset -= blocksize; + last_subpart = max3(trx->offset[0], trx->offset[1], + trx->offset[2]); + trx_size = max(trx->length, last_subpart + blocksize); + + /* + * Skip the TRX data. Decrease offset by block size as + * the next loop iteration will increase it. + */ + offset += roundup(trx_size, blocksize) - blocksize; continue; } |