Re: [RFC][PATCH] printf: Harden accessing pointer dereference in vsprintf()

[Steven Rostedt]

On Mon, 6 Jan 2025 15:29:01 -0800
Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> wrote:

> On Mon, 6 Jan 2025 at 14:25, Steven Rostedt <rostedt@xxxxxxxxxxx> wrote:
> >
> > Linus had suggested adding this kind of check[1]. This is a bit different
> > than Linus's solution as it utilizes copy_from_kernel_nofault() and doesn't
> > require calls to pagefault_disable() and extra labels.  
> 
> Yeah, and it generates horrendous code as a result.
> 

I guess the question is do we prefer horrendous code generated or what we see?

vsprintf() is used in critical paths, but I wonder how much these two
versions actually make a difference in performance? If they do, then yeah,
the open coded version would be better.

-- Steve