[lvc-project] [PATCH] PCI/IOV: "virtfn4294967295\0" requires 17 bytes

[Matthew Wilcox]

On Sun, Dec 18, 2022 at 03:21:39PM +0300, Alexey V. Vissarionov wrote:
> On 2022-12-18 19:57:02 +0900, Krzysztof Wilczyński wrote:
> 
>  > Thank you for sending the patch over! However, if possible,
>  > can you send it as plain text without any multi-part MIME
>  > involved?
> 
> ACK.
> 
>  > If possible, it would be nice to mention that this needed
>  > to make sure that there is enough space to correctly
>  > NULL-terminate the ID string.
> 
> ACK.
> 
> So, here goes the corrected text:
> 
> Although unlikely, the 'id' value may be as big as 4294967295
> (uint32_max) and "virtfn4294967295\0" would require 17 bytes
> instead of 16 to make sure that buffer has enough space to
> properly NULL-terminate the ID string.

Wait, what?  How can we get to a number that large for the virtual
function ID?  devfn is 8 bits, bus is a further 8 bits.  Sure, domain
is an extra 16 bits on top of that but I'm pretty sure that virtual
functions can't span multiple domains.  Unless that's changed recently?

Even if they can, we'd need to span 2^14 domains to get up to a billion
IDs.  That's a hell of a system and I think overflowing here is the
least of our problems.

So while this is typed as u32, I don't think it can get anywhere close.