Re: [PATCH v3 1/2] capability: add cap_isidentical

[Mateusz Guzik <mjguzik@gmail.com>]

On 2/28/23, Linus Torvalds <torvalds@linux-foundation.org> wrote:
> On Tue, Feb 28, 2023 at 11:39 AM Linus Torvalds
> <torvalds@linux-foundation.org> wrote:
>>
>> Call me crazy.
>

Hello crazy,

> I had to go through the patch with a find comb, because everything
> worked except for some reason network name resolution failed:
> systemd-resolved got a permission error on
>
>     Failed to listen on UDP socket 127.0.0.53:53: Permission denied
>
> Spot the insufficient fixup in my cut-and-paste capget() patch:
>
>   kdata[0].effective   = pE.val;
>         kdata[1].effective   = pE.val >> 32;
>   kdata[0].permitted   = pP.val;
>         kdata[1].permitted   = pP.val >> 32;
>   kdata[0].inheritable = pI.val;
>         kdata[0].inheritable = pI.val >> 32;
>
> Oops.
>
> But with that fixed, that patch actually does seem to work.
>

This is part of the crap which made me unwilling to do the clean up.

Unless there is a test suite (which I'm guessing there is not), I
think this warrants a prog which iterates over all methods with a
bunch of randomly generated capsets (+ maybe handpicked corner cases?)
and compares results new vs old. Otherwise I would feel very uneasy
signing off on the patch.

That said, nice cleanup if it works out :)

-- 
Mateusz Guzik <mjguzik gmail.com>