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From:   Paul Cercueil <paul@crapouillou.net>
To:     Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc:     Nathan Chancellor <natechancellor@gmail.com>,
        Nick Desaulniers <ndesaulniers@google.com>, od@zcrc.me,
        linux-mips@vger.kernel.org, linux-kernel@vger.kernel.org,
        clang-built-linux@googlegroups.com,
        Paul Cercueil <paul@crapouillou.net>, stable@vger.kernel.org
Subject: [PATCH] MIPS: boot: Fix unaligned access with CONFIG_MIPS_RAW_APPENDED_DTB
Date:   Wed, 16 Dec 2020 23:39:56 +0000
Message-Id: <20201216233956.280068-1-paul@crapouillou.net>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

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_le().

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@vger.kernel.org> # v4.7
Signed-off-by: Paul Cercueil <paul@crapouillou.net>
---
 arch/mips/boot/compressed/decompress.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/mips/boot/compressed/decompress.c b/arch/mips/boot/compressed/decompress.c
index c61c641674e6..47c07990432b 100644
--- a/arch/mips/boot/compressed/decompress.c
+++ b/arch/mips/boot/compressed/decompress.c
@@ -117,7 +117,7 @@ void decompress_kernel(unsigned long boot_heap_start)
 		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,
-- 
2.29.2