linux-kernel - [PATCH 1/6] arm64, vdso: Define vdso

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Date:   Mon,  5 Jun 2017 21:52:30 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     Kees Cook <keescook@...omium.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        Jisheng Zhang <jszhang@...vell.com>,
        linux-kernel@...r.kernel.org
Subject: [PATCH 1/6] arm64, vdso: Define vdso_{start,end} as array

Adjust vdso_{start|end} to be char arrays to avoid compile-time analysis
that flags "too large" memcmp() calls with CONFIG_FORTIFY_SOURCE.

Suggested-by: Mark Rutland <mark.rutland@....com>
Signed-off-by: Kees Cook <keescook@...omium.org>
Cc: Catalin Marinas <catalin.marinas@....com>
Cc: Will Deacon <will.deacon@....com>
Cc: Jisheng Zhang <jszhang@...vell.com>
---
 arch/arm64/kernel/vdso.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/arch/arm64/kernel/vdso.c b/arch/arm64/kernel/vdso.c
index 41b6e31f8f55..ae35f1855e06 100644
--- a/arch/arm64/kernel/vdso.c
+++ b/arch/arm64/kernel/vdso.c
@@ -37,7 +37,7 @@
 #include <asm/vdso.h>
 #include <asm/vdso_datapage.h>
 
-extern char vdso_start, vdso_end;
+extern char vdso_start[], vdso_end[];
 static unsigned long vdso_pages __ro_after_init;
 
 /*
@@ -125,14 +125,14 @@ static int __init vdso_init(void)
 	struct page **vdso_pagelist;
 	unsigned long pfn;
 
-	if (memcmp(&vdso_start, "\177ELF", 4)) {
+	if (memcmp(vdso_start, "\177ELF", 4)) {
 		pr_err("vDSO is not a valid ELF object!\n");
 		return -EINVAL;
 	}
 
-	vdso_pages = (&vdso_end - &vdso_start) >> PAGE_SHIFT;
+	vdso_pages = (vdso_end - vdso_start) >> PAGE_SHIFT;
 	pr_info("vdso: %ld pages (%ld code @ %p, %ld data @ %p)\n",
-		vdso_pages + 1, vdso_pages, &vdso_start, 1L, vdso_data);
+		vdso_pages + 1, vdso_pages, vdso_start, 1L, vdso_data);
 
 	/* Allocate the vDSO pagelist, plus a page for the data. */
 	vdso_pagelist = kcalloc(vdso_pages + 1, sizeof(struct page *),
@@ -145,7 +145,7 @@ static int __init vdso_init(void)
 
 
 	/* Grab the vDSO code pages. */
-	pfn = sym_to_pfn(&vdso_start);
+	pfn = sym_to_pfn(vdso_start);
 
 	for (i = 0; i < vdso_pages; i++)
 		vdso_pagelist[i + 1] = pfn_to_page(pfn + i);
-- 
2.7.4