linux-kernel - [PATCH 18/28] mm: enforce that vmap can't map pages executable

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Date:   Wed,  8 Apr 2020 13:59:16 +0200
From:   Christoph Hellwig <hch@....de>
To:     Andrew Morton <akpm@...ux-foundation.org>,
        "K. Y. Srinivasan" <kys@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        Wei Liu <wei.liu@...nel.org>, x86@...nel.org,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Laura Abbott <labbott@...hat.com>,
        Sumit Semwal <sumit.semwal@...aro.org>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>,
        Minchan Kim <minchan@...nel.org>,
        Nitin Gupta <ngupta@...are.org>
Cc:     Robin Murphy <robin.murphy@....com>,
        Christophe Leroy <christophe.leroy@....fr>,
        Peter Zijlstra <peterz@...radead.org>,
        linuxppc-dev@...ts.ozlabs.org, linux-hyperv@...r.kernel.org,
        dri-devel@...ts.freedesktop.org, linaro-mm-sig@...ts.linaro.org,
        linux-arch@...r.kernel.org, linux-mm@...ck.org,
        iommu@...ts.linux-foundation.org,
        linux-arm-kernel@...ts.infradead.org, linux-s390@...r.kernel.org,
        bpf@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH 18/28] mm: enforce that vmap can't map pages executable

To help enforcing the W^X protection don't allow remapping existing
pages as executable.

Based on patch from Peter Zijlstra <peterz@...radead.org>.

Signed-off-by: Christoph Hellwig <hch@....de>
---
 arch/x86/include/asm/pgtable_types.h | 6 ++++++
 include/asm-generic/pgtable.h        | 4 ++++
 mm/vmalloc.c                         | 2 +-
 3 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/pgtable_types.h b/arch/x86/include/asm/pgtable_types.h
index 947867f112ea..2e7c442cc618 100644
--- a/arch/x86/include/asm/pgtable_types.h
+++ b/arch/x86/include/asm/pgtable_types.h
@@ -282,6 +282,12 @@ typedef struct pgprot { pgprotval_t pgprot; } pgprot_t;
 
 typedef struct { pgdval_t pgd; } pgd_t;
 
+static inline pgprot_t pgprot_nx(pgprot_t prot)
+{
+	return __pgprot(pgprot_val(prot) | _PAGE_NX);
+}
+#define pgprot_nx pgprot_nx
+
 #ifdef CONFIG_X86_PAE
 
 /*
diff --git a/include/asm-generic/pgtable.h b/include/asm-generic/pgtable.h
index 329b8c8ca703..8c5f9c29698b 100644
--- a/include/asm-generic/pgtable.h
+++ b/include/asm-generic/pgtable.h
@@ -491,6 +491,10 @@ static inline int arch_unmap_one(struct mm_struct *mm,
 #define flush_tlb_fix_spurious_fault(vma, address) flush_tlb_page(vma, address)
 #endif
 
+#ifndef pgprot_nx
+#define pgprot_nx(prot)	(prot)
+#endif
+
 #ifndef pgprot_noncached
 #define pgprot_noncached(prot)	(prot)
 #endif
diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index 7356b3f07bd8..334c75251ddb 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -2390,7 +2390,7 @@ void *vmap(struct page **pages, unsigned int count,
 	if (!area)
 		return NULL;
 
-	if (map_kernel_range((unsigned long)area->addr, size, prot,
+	if (map_kernel_range((unsigned long)area->addr, size, pgprot_nx(prot),
 			pages) < 0) {
 		vunmap(area->addr);
 		return NULL;
-- 
2.25.1