[PATCH] [STABLE backport 4.9] arm64, vdso: Define vdso_{start,end} as array

[Arnd Bergmann]

From: Kees Cook <keescook@xxxxxxxxxxxx>

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@xxxxxxxxxxx>
Acked-by: Catalin Marinas <catalin.marinas@xxxxxxx>
Suggested-by: Mark Rutland <mark.rutland@xxxxxxx>
Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
Signed-off-by: Will Deacon <will.deacon@xxxxxxx>
Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
---
Backported to 4.9, which is lacking the rework from
2077be6783b5 ("arm64: Use __pa_symbol for kernel symbols")
---
 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 c9b9a5a322eb..c0f315ecfa7c 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;
 
 /*
@@ -124,14 +124,14 @@ static int __init vdso_init(void)
 	int i;
 	struct page **vdso_pagelist;
 
-	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 *),
@@ -144,7 +144,7 @@ static int __init vdso_init(void)
 
 	/* Grab the vDSO code pages. */
 	for (i = 0; i < vdso_pages; i++)
-		vdso_pagelist[i + 1] = pfn_to_page(PHYS_PFN(__pa(&vdso_start)) + i);
+		vdso_pagelist[i + 1] = pfn_to_page(PHYS_PFN(__pa(vdso_start)) + i);
 
 	vdso_spec[0].pages = &vdso_pagelist[0];
 	vdso_spec[1].pages = &vdso_pagelist[1];
-- 
2.20.0