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

[Greg KH]

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?

thanks,

greg k-h