Re: [PATCH] powerpc/ipic: Fix a bounds check in ipic_set_priority()

Michael Ellerman
2018-12-07T02:07:00Z

Christophe LEROY <christophe.leroy@c-s.fr> writes:
> Le 05/12/2018 à 04:26, Michael Ellerman a écrit :
>> Hi Dan,
>>
>> Thanks for the patch.
>>
>> Dan Carpenter <dan.carpenter@oracle.com> writes:
>>> The ipic_info[] array only has 95 elements so I have made the bounds
>>> check smaller to prevent a read overflow. It was Smatch that found
>>> this issue:
>>>
>>> arch/powerpc/sysdev/ipic.c:784 ipic_set_priority()
>>> error: buffer overflow 'ipic_info' 95 <= 127
>>>
>>> Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
>>> ---
>>> I wasn't able to find any callers of this code. Maybe we removed the
>>> last one in commit b9f0f1bb2bca ("[POWERPC] Adapt ipic driver to new
>>> host_ops interface, add set_irq_type to set IRQ sense"). So perhaps we
>>> should just remove it. I'm not really comfortable doing that myself,
>>> because I don't know the code well enough and can't build test
>>> it properly.
>>
>> Hah wow, last usage removed in 2006!
>>
>> I don't see any mention of it since then, so I'll remove it. If it
>> breaks something we can put it back.
>>
>> Can smatch help us find things like this that are defined non-static but
>> never used?
>>
>
> I think we have to do that carrefully. Some of those functions might be
> used by out-of-tree boards.

We don't keep unused code around for out-of-tree boards.

Either the out-of-tree code should be merged upstream, or you can
maintain whatever extra functions you need as part of your out-of-tree
code base.

> I'm thinking especially at ipic_get_mcp_status() and
> ipic_set_mcp_status(). They are used in my 832x boards's machine check
> handler to know when a machine check is a timeout from the 832x watchdog.

Thanks for pointing them out, I'll send a patch to remove them :)

But seriously, why is your machine check code not in-tree, is there some
reason you can't merge it?

cheers