[PATCH v6 31/39] kasan, vmalloc: only tag normal vmalloc allocations

[Vasily Gorbik]

On Tue, Mar 08, 2022 at 04:30:46PM +0100, Andrey Konovalov wrote:
> On Tue, Mar 8, 2022 at 4:17 PM Vasily Gorbik <gor at linux.ibm.com> wrote:
> >
> > On Mon, Jan 24, 2022 at 07:05:05PM +0100, andrey.konovalov at linux.dev wrote:
> > > From: Andrey Konovalov <andreyknvl at google.com>
> > >
> > > The kernel can use to allocate executable memory. The only supported way
> > > to do that is via __vmalloc_node_range() with the executable bit set in
> > > the prot argument. (vmap() resets the bit via pgprot_nx()).
> > >
> > > Once tag-based KASAN modes start tagging vmalloc allocations, executing
> > > code from such allocations will lead to the PC register getting a tag,
> > > which is not tolerated by the kernel.
> > >
> > > Only tag the allocations for normal kernel pages.
> > >
> > > Signed-off-by: Andrey Konovalov <andreyknvl at google.com>
> >
> > This breaks s390 and produce huge amount of false positives.
> > I haven't been testing linux-next with KASAN for while, now tried it with
> > next-20220308 and bisected false positives to this commit.
> >
> > Any idea what is going wrong here?
> 
> Could you try the attached fix?

Wow, that was quick!
Yes, it fixes the issue for s390, kasan tests pass as well.
Thank you!