Re: [PATCH] arm64: lib: use C string functions with KASAN enabled.

Mark Rutland
2018-09-10T12:53:11Z

On Mon, Sep 10, 2018 at 12:33:22PM +0100, Mark Rutland wrote:
> On Fri, Sep 07, 2018 at 06:48:10PM +0300, Andrey Ryabinin wrote:
> > On 09/07/2018 05:56 PM, Will Deacon wrote:
> > > I don't understand this bit: efistub uses the __pi_ prefixed
> > > versions of the routines, so why do we need to declare them as weak?
> >
> > Weak needed because we can't have two non-weak functions with the same
> > name.
> >
> > Alternative approach would be to never use e.g. "strlen" name for asm
> > implementation of strlen() under CONFIG_KASAN=y. But that would
> > require adding some special ENDPIPROC_KASAN() macro since we want
> > __pi_strlen() to point to the asm_strlen().
>
> Somehow, what we have today works with CONFIG_FORTIFY_SOURCE, which
> AFAICT would suffer from texactly the same problem with things like
> memcpy.
>
> So either we're getting away with that by chance already (and should fix
> that regardless of this patch), or this is not actually a problem.

I now see those functions are marked weak in the assembly
implementation; sorry for the noise.

Regardless, I still think it's preferable to avoid weak wherever
possible.

I have a couple of local patches to do that for KASAN, though it's not
clear to me how that should interact with FORTIFY_SOURCE.

Thanks,
Mark.