Re: [PATCH] tty: vt: keyboard: do not copy an extra-byte in copy_to_user

Ajay Garg
2021-11-10T09:33:07Z

> >
> > That's right Pavel.
> > Every function must work correctly as it "advertises", instead of
> > relying on "chancy correctness" of the calls leading to the method.
>
> That is not how the kernel works, sorry. Otherwise every function would
> have to always verify all parameters passed to them, causing slow downs
> and redundant checks everywhere.
>

Hmm, agreed. Every cycle saved in the kernel is performance gained.

That's why, the RFC for strlscpy [1] makes all the more sense, as it
would save cpu cycles by removing the requirement to check the
return-value for overflows/underflows (including the "issue" I am
trying to address in this particular thread, and which actually lead
to the RFC for strlscpy].

P.S. :

I am not an egoistic person, who wants to get into unnecessary fights
just to upheld one's ego.
All I am trying is to suggest improvements, that

* make things faster.
* keeps code to as minimum as possible.
* makes developers' lives as comfortable as possible.

[1]
https://lore.kernel.org/linux-hardening/CAHP4M8WnLA0780yN+bpuuCtir+DLJRxe0atAiLbZO0bTGf6J-Q@mail.gmail.com/T/#m4a3f524eefe283a42430905fa4c0dfc2c37b2819

Thanks and Regards,
Ajay