linux-kernel - [PATCH] [STABLE backport 4.9] arm64, vdso: Define vdso

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Date:   Fri,  5 Jul 2019 20:55:50 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     stable@...nel.org
Cc:     Sasha Levin <alexander.levin@...rosoft.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Kees Cook <keescook@...omium.org>,
        Jisheng Zhang <jszhang@...vell.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Mark Rutland <mark.rutland@....com>,
        Will Deacon <will.deacon@....com>,
        Arnd Bergmann <arnd@...db.de>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: [PATCH] [STABLE backport 4.9] arm64, vdso: Define vdso_{start,end} as array

From: Kees Cook <keescook@...omium.org>

Commit dbbb08f500d6146398b794fdc68a8e811366b451 upstream.

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

Cc: Jisheng Zhang <jszhang@...vell.com>
Acked-by: Catalin Marinas <catalin.marinas@....com>
Suggested-by: Mark Rutland <mark.rutland@....com>
Signed-off-by: Kees Cook <keescook@...omium.org>
Signed-off-by: Will Deacon <will.deacon@....com>
Signed-off-by: Arnd Bergmann <arnd@...db.de>
---
Backported to 4.4, which predates the rework from
2077be6783b5 ("arm64: Use __pa_symbol for kernel symbols") and
5a9e3e156ec1 ("arm64: apply __ro_after_init to some objects")
---
 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 97bc68f4c689..908bc5ab94c1 100644
--- a/arch/arm64/kernel/vdso.c
+++ b/arch/arm64/kernel/vdso.c
@@ -36,7 +36,7 @@
 #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;
 static struct page **vdso_pagelist;
 
@@ -115,14 +115,14 @@ static int __init vdso_init(void)
 {
 	int i;
 
-	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 *),
@@ -135,7 +135,7 @@ static int __init vdso_init(void)
 
 	/* Grab the vDSO code pages. */
 	for (i = 0; i < vdso_pages; i++)
-		vdso_pagelist[i + 1] = virt_to_page(&vdso_start + i * PAGE_SIZE);
+		vdso_pagelist[i + 1] = virt_to_page(vdso_start + i * PAGE_SIZE);
 
 	/* Populate the special mapping structures */
 	vdso_spec[0] = (struct vm_special_mapping) {
-- 
2.20.0