Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753252AbdFGXi1 (ORCPT ); Wed, 7 Jun 2017 19:38:27 -0400 Received: from wtarreau.pck.nerim.net ([62.212.114.60]:50618 "EHLO 1wt.eu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753091AbdFGXEn (ORCPT ); Wed, 7 Jun 2017 19:04:43 -0400 From: Willy Tarreau To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, linux@roeck-us.net Cc: Marcelo Henrique Cerri , Heiko Carstens , Martin Schwidefsky , Willy Tarreau Subject: [PATCH 3.10 207/250] s390/decompressor: fix initrd corruption caused by bss clear Date: Thu, 8 Jun 2017 00:59:53 +0200 Message-Id: <1496876436-32402-208-git-send-email-w@1wt.eu> X-Mailer: git-send-email 2.8.0.rc2.1.gbe9624a In-Reply-To: <1496876436-32402-1-git-send-email-w@1wt.eu> References: <1496876436-32402-1-git-send-email-w@1wt.eu> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3275 Lines: 83 From: Marcelo Henrique Cerri commit d82c0d12c92705ef468683c9b7a8298dd61ed191 upstream. Reorder the operations in decompress_kernel() to ensure initrd is moved to a safe location before the bss section is zeroed. During decompression bss can overlap with the initrd and this can corrupt the initrd contents depending on the size of the compressed kernel (which affects where the initrd is placed by the bootloader) and the size of the bss section of the decompressor. Also use the correct initrd size when checking for overlaps with parmblock. Fixes: 06c0dd72aea3 ([S390] fix boot failures with compressed kernels) Reviewed-by: Joy Latten Reviewed-by: Vineetha HariPai Signed-off-by: Marcelo Henrique Cerri Signed-off-by: Heiko Carstens Signed-off-by: Martin Schwidefsky Signed-off-by: Willy Tarreau --- arch/s390/boot/compressed/misc.c | 35 +++++++++++++++++++---------------- 1 file changed, 19 insertions(+), 16 deletions(-) diff --git a/arch/s390/boot/compressed/misc.c b/arch/s390/boot/compressed/misc.c index c4c6a1c..05ab882 100644 --- a/arch/s390/boot/compressed/misc.c +++ b/arch/s390/boot/compressed/misc.c @@ -138,31 +138,34 @@ static void check_ipl_parmblock(void *start, unsigned long size) unsigned long decompress_kernel(void) { - unsigned long output_addr; - unsigned char *output; + void *output, *kernel_end; - output_addr = ((unsigned long) &_end + HEAP_SIZE + 4095UL) & -4096UL; - check_ipl_parmblock((void *) 0, output_addr + SZ__bss_start); - memset(&_bss, 0, &_ebss - &_bss); - free_mem_ptr = (unsigned long)&_end; - free_mem_end_ptr = free_mem_ptr + HEAP_SIZE; - output = (unsigned char *) output_addr; + output = (void *) ALIGN((unsigned long) &_end + HEAP_SIZE, PAGE_SIZE); + kernel_end = output + SZ__bss_start; + check_ipl_parmblock((void *) 0, (unsigned long) kernel_end); #ifdef CONFIG_BLK_DEV_INITRD /* * Move the initrd right behind the end of the decompressed - * kernel image. + * kernel image. This also prevents initrd corruption caused by + * bss clearing since kernel_end will always be located behind the + * current bss section.. */ - if (INITRD_START && INITRD_SIZE && - INITRD_START < (unsigned long) output + SZ__bss_start) { - check_ipl_parmblock(output + SZ__bss_start, - INITRD_START + INITRD_SIZE); - memmove(output + SZ__bss_start, - (void *) INITRD_START, INITRD_SIZE); - INITRD_START = (unsigned long) output + SZ__bss_start; + if (INITRD_START && INITRD_SIZE && kernel_end > (void *) INITRD_START) { + check_ipl_parmblock(kernel_end, INITRD_SIZE); + memmove(kernel_end, (void *) INITRD_START, INITRD_SIZE); + INITRD_START = (unsigned long) kernel_end; } #endif + /* + * Clear bss section. free_mem_ptr and free_mem_end_ptr need to be + * initialized afterwards since they reside in bss. + */ + memset(&_bss, 0, &_ebss - &_bss); + free_mem_ptr = (unsigned long) &_end; + free_mem_end_ptr = free_mem_ptr + HEAP_SIZE; + puts("Uncompressing Linux... "); decompress(input_data, input_len, NULL, NULL, output, NULL, error); puts("Ok, booting the kernel.\n"); -- 2.8.0.rc2.1.gbe9624a