linux-kernel - [PATCH 4.9 139/145] arm64: fix warning about swapper_pg

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Date:   Fri, 23 Feb 2018 19:27:25 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Mark Rutland <mark.rutland@....com>,
        Arnd Bergmann <arnd@...db.de>,
        Will Deacon <will.deacon@....com>
Subject: [PATCH 4.9 139/145] arm64: fix warning about swapper_pg_dir overflow

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Arnd Bergmann <arnd@...db.de>

commit 12f043ff2b28fa64c9123b454cbe30a8a9e1967e upstream.

With 4 levels of 16KB pages, we get this warning about the fact that we are
copying a whole page into an array that is declared as having only two pointers
for the top level of the page table:

arch/arm64/mm/mmu.c: In function 'paging_init':
arch/arm64/mm/mmu.c:528:2: error: 'memcpy' writing 16384 bytes into a region of size 16 overflows the destination [-Werror=stringop-overflow=]

This is harmless since we actually reserve a whole page in the definition of the
array that comes from, and just the extern declaration is short. The pgdir
is initialized to zero either way, so copying the actual entries here seems
like the best solution.

Acked-by: Ard Biesheuvel <ard.biesheuvel@...aro.org>
Acked-by: Mark Rutland <mark.rutland@....com>
Signed-off-by: Arnd Bergmann <arnd@...db.de>
Signed-off-by: Will Deacon <will.deacon@....com>
[slightly adapted to apply on 4.9]
Signed-off-by: Arnd Bergmann <arnd@...db.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 arch/arm64/mm/mmu.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -479,7 +479,7 @@ void __init paging_init(void)
 	 * To do this we need to go via a temporary pgd.
 	 */
 	cpu_replace_ttbr1(__va(pgd_phys));
-	memcpy(swapper_pg_dir, pgd, PAGE_SIZE);
+	memcpy(swapper_pg_dir, pgd, PGD_SIZE);
 	cpu_replace_ttbr1(swapper_pg_dir);
 
 	pgd_clear_fixmap();