linux-kernel - [PATCH 4.9 02/35] MIPS: boot: Fix unaligned access with CONFIG_MIPS_RAW_APPENDED

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Message-Id: <20210122135732.456737657@linuxfoundation.org>
Date:   Fri, 22 Jan 2021 15:10:04 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Paul Cercueil <paul@...pouillou.net>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Philippe Mathieu-Daudé <f4bug@...at.org>,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>
Subject: [PATCH 4.9 02/35] MIPS: boot: Fix unaligned access with CONFIG_MIPS_RAW_APPENDED_DTB

From: Paul Cercueil <paul@...pouillou.net>

commit 4d4f9c1a17a3480f8fe523673f7232b254d724b7 upstream.

The compressed payload is not necesarily 4-byte aligned, at least when
compiling with Clang. In that case, the 4-byte value appended to the
compressed payload that corresponds to the uncompressed kernel image
size must be read using get_unaligned_le32().

This fixes Clang-built kernels not booting on MIPS (tested on a Ingenic
JZ4770 board).

Fixes: b8f54f2cde78 ("MIPS: ZBOOT: copy appended dtb to the end of the kernel")
Cc: <stable@...r.kernel.org> # v4.7
Signed-off-by: Paul Cercueil <paul@...pouillou.net>
Reviewed-by: Nick Desaulniers <ndesaulniers@...gle.com>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@...at.org>
Signed-off-by: Thomas Bogendoerfer <tsbogend@...ha.franken.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 arch/mips/boot/compressed/decompress.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/arch/mips/boot/compressed/decompress.c
+++ b/arch/mips/boot/compressed/decompress.c
@@ -17,6 +17,7 @@
 #include <linux/libfdt.h>
 
 #include <asm/addrspace.h>
+#include <asm/unaligned.h>
 
 /*
  * These two variables specify the free mem region
@@ -124,7 +125,7 @@ void decompress_kernel(unsigned long boo
 		dtb_size = fdt_totalsize((void *)&__appended_dtb);
 
 		/* last four bytes is always image size in little endian */
-		image_size = le32_to_cpup((void *)&__image_end - 4);
+		image_size = get_unaligned_le32((void *)&__image_end - 4);
 
 		/* copy dtb to where the booted kernel will expect it */
 		memcpy((void *)VMLINUX_LOAD_ADDRESS_ULL + image_size,