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- From 237ea0d4762cc14d0fc80e80d61f0f08e1050c7f Mon Sep 17 00:00:00 2001
- From: =?UTF-8?q?Rafa=C5=82=20Mi=C5=82ecki?= <rafal@milecki.pl>
- Date: Thu, 12 Apr 2018 07:24:52 +0200
- Subject: [PATCH] mtd: bcm47xxpart: improve handling TRX partition size
- MIME-Version: 1.0
- Content-Type: text/plain; charset=UTF-8
- Content-Transfer-Encoding: 8bit
- 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>
- ---
- drivers/mtd/bcm47xxpart.c | 22 ++++++++++++++++++----
- 1 file changed, 18 insertions(+), 4 deletions(-)
- --- a/drivers/mtd/bcm47xxpart.c
- +++ b/drivers/mtd/bcm47xxpart.c
- @@ -268,6 +268,8 @@ static int bcm47xxpart_parse(struct mtd_
- /* 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",
- @@ -277,11 +279,23 @@ static int bcm47xxpart_parse(struct mtd_
- 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;
- }
-
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