Patch "x86-64/Xen: eliminate W+X mappings" has been added to the 4.14-stable tree

[<gregkh@linuxfoundation.org>]

This is a note to let you know that I've just added the patch titled

    x86-64/Xen: eliminate W+X mappings

to the 4.14-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     x86-64-xen-eliminate-w-x-mappings.patch
and it can be found in the queue-4.14 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From foo@baz Wed Feb 28 16:23:28 CET 2018
From: Jan Beulich <JBeulich@suse.com>
Date: Mon, 18 Dec 2017 09:37:45 -0700
Subject: x86-64/Xen: eliminate W+X mappings

From: Jan Beulich <JBeulich@suse.com>


[ Upstream commit 2cc42bac1c795f75fcc062b95c6ca7ac1b84d5d8 ]

A few thousand such pages are usually left around due to the re-use of
L1 tables having been provided by the hypervisor (Dom0) or tool stack
(DomU). Set NX in the direct map variant, which needs to be done in L2
due to the dual use of the re-used L1s.

For x86_configure_nx() to actually do what it is supposed to do, call
get_cpu_cap() first. This was broken by commit 4763ed4d45 ("x86, mm:
Clean up and simplify NX enablement") when switching away from the
direct EFER read.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: Sasha Levin <alexander.levin@verizon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 arch/x86/xen/enlighten_pv.c |    3 +++
 arch/x86/xen/mmu_pv.c       |   12 ++++++++++++
 2 files changed, 15 insertions(+)

--- a/arch/x86/xen/enlighten_pv.c
+++ b/arch/x86/xen/enlighten_pv.c
@@ -88,6 +88,8 @@
 #include "multicalls.h"
 #include "pmu.h"
 
+#include "../kernel/cpu/cpu.h" /* get_cpu_cap() */
+
 void *xen_initial_gdt;
 
 static int xen_cpu_up_prepare_pv(unsigned int cpu);
@@ -1257,6 +1259,7 @@ asmlinkage __visible void __init xen_sta
 	__userpte_alloc_gfp &= ~__GFP_HIGHMEM;
 
 	/* Work out if we support NX */
+	get_cpu_cap(&boot_cpu_data);
 	x86_configure_nx();
 
 	/* Get mfn list */
--- a/arch/x86/xen/mmu_pv.c
+++ b/arch/x86/xen/mmu_pv.c
@@ -1902,6 +1902,18 @@ void __init xen_setup_kernel_pagetable(p
 	/* Graft it onto L4[511][510] */
 	copy_page(level2_kernel_pgt, l2);
 
+	/*
+	 * Zap execute permission from the ident map. Due to the sharing of
+	 * L1 entries we need to do this in the L2.
+	 */
+	if (__supported_pte_mask & _PAGE_NX) {
+		for (i = 0; i < PTRS_PER_PMD; ++i) {
+			if (pmd_none(level2_ident_pgt[i]))
+				continue;
+			level2_ident_pgt[i] = pmd_set_flags(level2_ident_pgt[i], _PAGE_NX);
+		}
+	}
+
 	/* Copy the initial P->M table mappings if necessary. */
 	i = pgd_index(xen_start_info->mfn_list);
 	if (i && i < pgd_index(__START_KERNEL_map))


Patches currently in stable-queue which might be from JBeulich@suse.com are

queue-4.14/x86-64-xen-eliminate-w-x-mappings.patch