Re: [PATCH 1/2] mm/madvise: introduce PR_MADV_SELF flag to process_madvise()

[Lorenzo Stoakes]

On Mon, Sep 23, 2024 at 09:49:43PM GMT, Arnd Bergmann wrote:
> On Mon, Sep 23, 2024, at 19:34, Lorenzo Stoakes wrote:
> > On Mon, Sep 23, 2024 at 11:56:06AM GMT, Shakeel Butt wrote:
> >
> > +	/* Require PTRACE_MODE_READ to avoid leaking ASLR metadata. */
> > +	mm = mm_access(task, PTRACE_MODE_READ_FSCREDS);
> > +	if (IS_ERR_OR_NULL(mm)) {
> > +		ret = IS_ERR(mm) ? PTR_ERR(mm) : -ESRCH;
> > +		goto release_task;
> > +	}
>
> Any chance we can fix mm_access() to not be able to return
> a NULL pointer and an error pointer?  IS_ERR_OR_NULL() is
> usually an indication of a confusing API, and this is
> clearly one of them, given that only one of the
> callers actually wants the NULL value instead of -ESRCH.
>
>     Arnd

Agreed, this should be fixed. I think it'd be a bit out of the scope of
this series so will send something separately for this.