Re: [PATCH] block: fix Amiga partition support for disks >= 1 TB

Michael Schmitz
2018-07-02T22:34:17Z

Hi Kars,

thanks for your comments - will do.

Cheers,

Michael

On Mon, Jul 2, 2018 at 6:38 PM, Kars de Jong <jongk@linux-m68k.org> wrote:
> Op ma 2 jul. 2018 om 07:29 schreef Michael Schmitz <schmitzmic@gmail.com>:
>> @@ -98,6 +101,79 @@ int amiga_partition(struct parsed_partitions *state)
>> if (checksum_block((__be32 *)pb, be32_to_cpu(pb->pb_SummedLongs) & 0x7F) != 0 )
>> continue;
>>
>> + /* RDB gives us more than enough rope to hang ourselves with,
>> + * many times over (2^128 bytes if all fields max out).
>> + * Some careful checks are in order.
>> + */
>> +
>> + /* CylBlocks is total number of blocks per cylinder */
>> + cylblk = be32_to_cpu(pb->pb_Environment[3]) *
>> + be32_to_cpu(pb->pb_Environment[5]);
>> +
>
> Could you please create #defines for all these magic offsets in pb_Environment?
> Below are a few more.
> This makes the code much more readable.
> Thanks!
>
>> + /* check for consistency with RDB defined CylBlocks */
>> + if (cylblk > be32_to_cpu(rdb->rdb_CylBlocks)) {
>> + pr_err("Dev %s: cylblk 0x%lx > rdb_CylBlocks 0x%x!\n",
>> + bdevname(state->bdev, b),
>> + (unsigned long) cylblk,
>> + be32_to_cpu(rdb->rdb_CylBlocks));
>> + }
>> +
>> + /* check for potential overflows - we are going to multiply
>> + * three 32 bit numbers to one 64 bit result later!
>> + * Condition 1: nr_heads * sects_per_track must fit u32!
>> + * NB: This is a HARD limit for AmigaDOS. We don't care much.
>> + */
>> +
>> + if (cylblk > UINT_MAX) {
>> + pr_err("Dev %s: hds*sects 0x%lx > UINT_MAX!\n",
>> + bdevname(state->bdev, b),
>> + (unsigned long) cylblk);
>> +
>> + /* lop off low 32 bits */
>> + cylblk_res = cylblk >> 32;
>> +
>> + /* check for further overflow in end result */
>> + if (be32_to_cpu(pb->pb_Environment[9]) *
>> + cylblk_res * blksize > UINT_MAX) {
>> + pr_err("Dev %s: start_sect overflows u64!\n",
>> + bdevname(state->bdev, b));
>> + res = -1;
>> + goto rdb_done;
>> + }
>> +
>> + if (be32_to_cpu(pb->pb_Environment[10]) *
>> + cylblk_res * blksize > UINT_MAX) {
>> + pr_err("Dev %s: end_sect overflows u64!\n",
>> + bdevname(state->bdev, b));
>> + res = -1;
>> + goto rdb_done;
>> + }
>> + }
>> +
>> + /* Condition 2: even if CylBlocks did not overflow, the end
>> + * result must still fit u64!
>> + */
>> +
>> + /* how many bits above 32 in cylblk * blksize ? */
>> + if (cylblk*blksize > (u64) UINT_MAX)
>> + blk_shift = ilog2(cylblk*blksize) - 32;
>> +
>> + if (be32_to_cpu(pb->pb_Environment[9])
>> + > (u64) UINT_MAX>>blk_shift) {
>> + pr_err("Dev %s: start_sect overflows u64!\n",
>> + bdevname(state->bdev, b));
>> + res = -1;
>> + goto rdb_done;
>> + }
>> +
>> + if (be32_to_cpu(pb->pb_Environment[10])
>> + > (u64) UINT_MAX>>blk_shift) {
>> + pr_err("Dev %s: end_sect overflows u64!\n",
>> + bdevname(state->bdev, b));
>> + res = -1;
>> + goto rdb_done;
>> + }
>> +
>> /* Tell Kernel about it */
>>
>> nr_sects = (be32_to_cpu(pb->pb_Environment[10]) + 1 -