Re: [PATCH] block: bugfix for Amiga partition overflow check patch

[Michael Schmitz <schmitzmic@gmail.com>]

Hi Adrian,

Am 04.07.2023 um 17:48 schrieb John Paul Adrian Glaubitz:
>>>
>>> Have we actually agreed now that this is a bug and not just an effect of the
>>> corrupted RDB that Christian provided?
>>
>> The RDB was perfectly fine. Due to 32 bit integer arithmetic overflow,
>> old RDB code passed an incorrect partition size to put_partition(),
>> and instead of rejecting a partition that extends past the end of the
>> disk, put_partition() truncated the size.
>
> OK, so using "-1" as an end-of-disk partition marker is fine, but it was just
> the partition size recorded in Christian's RDB that was incorrect, correct?

No, the partition size in the RDB was correct (valid, end cylinder 
before end of disk). The partition size seen by user space tools when 
running the old kernels was incorrect. That lead to the filesystem size 
exceeding the partition size, which only came to light once the overflow 
fixes had gone in.

I know it does sound like semantic sophism, but we have to be clear that 
what the user put in the partition block is definite. I haven't had much 
luck with heuristics in kernel code lately...

>>>
>>>> Jens - is the bugfix patch enough, or do you need a new version of the
>>>> entire series?
>>>
>>> But the series has already been applied and released in 6.4, hasn't it?
>>
>> That's right - I wasn't sure whether it had already gone upstream (but
>> even then, squeezing a bugfix in with an accepted patch isn't usually done).
>
> It's even released already ;-). That's why Christian ran into the problem in the
> first place.

I had hoped he'd spotted it in linux-block ...

Cheers,

	Michael


>
> Adrian
>