Re: [PATCHv4] MMC: MMC boot partitions support.

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On Thu, Mar 31, 2011 at 2:37 PM, Chris Ball <cjb@xxxxxxxxxx> wrote:
> Hi,
>
> On Thu, Mar 31 2011, Andrei Warkentin wrote:
>> Plus what if you do intend to have a file system there? Other than
>> complexity and non-obvious usage, I don't see
>> anything gained by this. I wouldn't worry about ways of misusing this.
>> As I've said, in the only case it matters (some embedded device
>> booting from the boot partition), the user would have to gain root
>> access, build a kernel giving access to the boot partitions and be
>> able to boot into it. So a warning in Kconfig is sufficient.
>>
>> If you guys feel concerned, then we can add another Kconfig option
>> that will allow write access to the boot partitions.
>
> I'm willing to come around to saying that the risk is acceptable, and
> that people who overwrite /dev/mmcblk0b0 on their rooted Android phones
> won't blame us (at least, not deservedly) for it.
>
> But I'm still concerned after your Kconfig options are added, because
> I'm just not reassured by Kconfig options in principle, because of the
> case where *the person who built the kernel* is not the same as the
> *user who is running commands*.  Imagine that CyanogenMod (or even
> Qualcomm!) distributes a kernel with this Kconfig option turned on --
> because they don't realize how dangerous it is, perhaps, or because they
> had a use for it during development -- to see where I'm coming from.
>
> Now, the presence of block devices that brick machines when overwritten
> isn't a new phenomenon, so we've got a fair amount of precedence behind
> us if we simply expose what we see and expect that users won't do
> something unrecoverable.  But I'm trying to think about if there's
> anything we can do to *minimize* that risk, and have people know what's
> going on before they do something they shouldn't.  (I think I like Arnd's
> suggestion of explicitly having "boot" in the device name rather than
> just "b", because that does lend a feeling of "this partition is really
> important".)

Yup I think having 'boot' in there (as in mmcblk0boot0) is a good
idea. I also think having boot write support as a separate
configuration option is also a good idea,
so I'll add that in. I think that should help minimize the risk.

A
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