[PATCH][for-stable] arm64: set UXN on swapper page tables

[Will Deacon]

On Mon, Aug 08, 2022 at 03:23:55PM +0200, Greg KH wrote:
> On Mon, Aug 08, 2022 at 01:53:21PM +0100, Will Deacon wrote:
> > From: Peter Collingbourne <pcc at google.com>
> > 
> > [ This issue was fixed upstream by accident in c3cee924bd85 ("arm64:
> >   head: cover entire kernel image in initial ID map") as part of a
> >   large refactoring of the arm64 boot flow. This simple fix is therefore
> >   preferred for -stable backporting ]
> > 
> > On a system that implements FEAT_EPAN, read/write access to the idmap
> > is denied because UXN is not set on the swapper PTEs. As a result,
> > idmap_kpti_install_ng_mappings panics the kernel when accessing
> > __idmap_kpti_flag. Fix it by setting UXN on these PTEs.
> > 
> > Fixes: 18107f8a2df6 ("arm64: Support execute-only permissions with Enhanced PAN")
> > Cc: <stable at vger.kernel.org> # 5.15
> > Link: https://linux-review.googlesource.com/id/Ic452fa4b4f74753e54f71e61027e7222a0fae1b1
> > Signed-off-by: Peter Collingbourne <pcc at google.com>
> > Acked-by: Will Deacon <will at kernel.org>
> > Cc: Ard Biesheuvel <ardb at kernel.org>
> > Cc: Catalin Marinas <catalin.marinas at arm.com>
> > Link: https://lore.kernel.org/r/20220719234909.1398992-1-pcc@google.com
> > Signed-off-by: Will Deacon <will at kernel.org>
> > ---
> >  arch/arm64/include/asm/kernel-pgtable.h | 4 ++--
> >  arch/arm64/kernel/head.S                | 2 +-
> >  2 files changed, 3 insertions(+), 3 deletions(-)
> 
> So this should be added to 5.15.y, 5.18.y, and 5.19.y?  Or some subset?

Yes, all of them. Basically anything still being updated which is >= 5.15
and <= 5.19.

Thanks,

Will