From 5dcd14ecd41ea2b3ae3295a9b30d98769d52165f Mon Sep 17 00:00:00 2001 From: "H. Peter Anvin" Date: Tue, 29 Jan 2013 01:05:24 -0800 Subject: [PATCH] x86, boot: Sanitize boot_params if not zeroed on creation Use the new sentinel field to detect bootloaders which fail to follow protocol and don't initialize fields in struct boot_params that they do not explicitly initialize to zero. Based on an original patch and research by Yinghai Lu. Changed by hpa to be invoked both in the decompression path and in the kernel proper; the latter for the case where a bootloader takes over decompression. Originally-by: Yinghai Lu Link: http://lkml.kernel.org/r/1359058816-7615-26-git-send-email-yinghai@kernel.org Signed-off-by: H. Peter Anvin --- arch/x86/boot/compressed/misc.c | 2 ++ arch/x86/boot/compressed/misc.h | 1 + arch/x86/include/asm/bootparam_utils.h | 38 ++++++++++++++++++++++++++ arch/x86/kernel/head32.c | 3 ++ arch/x86/kernel/head64.c | 2 ++ 5 files changed, 46 insertions(+) create mode 100644 arch/x86/include/asm/bootparam_utils.h diff --git a/arch/x86/boot/compressed/misc.c b/arch/x86/boot/compressed/misc.c index 88f7ff6da404..7cb56c6ca351 100644 --- a/arch/x86/boot/compressed/misc.c +++ b/arch/x86/boot/compressed/misc.c @@ -325,6 +325,8 @@ asmlinkage void decompress_kernel(void *rmode, memptr heap, { real_mode = rmode; + sanitize_boot_params(real_mode); + if (real_mode->screen_info.orig_video_mode == 7) { vidmem = (char *) 0xb0000; vidport = 0x3b4; diff --git a/arch/x86/boot/compressed/misc.h b/arch/x86/boot/compressed/misc.h index 0e6dc0ee0eea..674019d8e235 100644 --- a/arch/x86/boot/compressed/misc.h +++ b/arch/x86/boot/compressed/misc.h @@ -18,6 +18,7 @@ #include #include #include +#include #define BOOT_BOOT_H #include "../ctype.h" diff --git a/arch/x86/include/asm/bootparam_utils.h b/arch/x86/include/asm/bootparam_utils.h new file mode 100644 index 000000000000..5b5e9cb774b5 --- /dev/null +++ b/arch/x86/include/asm/bootparam_utils.h @@ -0,0 +1,38 @@ +#ifndef _ASM_X86_BOOTPARAM_UTILS_H +#define _ASM_X86_BOOTPARAM_UTILS_H + +#include + +/* + * This file is included from multiple environments. Do not + * add completing #includes to make it standalone. + */ + +/* + * Deal with bootloaders which fail to initialize unknown fields in + * boot_params to zero. The list fields in this list are taken from + * analysis of kexec-tools; if other broken bootloaders initialize a + * different set of fields we will need to figure out how to disambiguate. + * + */ +static void sanitize_boot_params(struct boot_params *boot_params) +{ + if (boot_params->sentinel) { + /*fields in boot_params are not valid, clear them */ + memset(&boot_params->olpc_ofw_header, 0, + (char *)&boot_params->alt_mem_k - + (char *)&boot_params->olpc_ofw_header); + memset(&boot_params->kbd_status, 0, + (char *)&boot_params->hdr - + (char *)&boot_params->kbd_status); + memset(&boot_params->_pad7[0], 0, + (char *)&boot_params->edd_mbr_sig_buffer[0] - + (char *)&boot_params->_pad7[0]); + memset(&boot_params->_pad8[0], 0, + (char *)&boot_params->eddbuf[0] - + (char *)&boot_params->_pad8[0]); + memset(&boot_params->_pad9[0], 0, sizeof(boot_params->_pad9)); + } +} + +#endif /* _ASM_X86_BOOTPARAM_UTILS_H */ diff --git a/arch/x86/kernel/head32.c b/arch/x86/kernel/head32.c index c18f59d10101..6773c918b8cc 100644 --- a/arch/x86/kernel/head32.c +++ b/arch/x86/kernel/head32.c @@ -18,6 +18,7 @@ #include #include #include +#include static void __init i386_default_early_setup(void) { @@ -30,6 +31,8 @@ static void __init i386_default_early_setup(void) void __init i386_start_kernel(void) { + sanitize_boot_params(&boot_params); + memblock_reserve(__pa_symbol(&_text), __pa_symbol(&__bss_stop) - __pa_symbol(&_text)); diff --git a/arch/x86/kernel/head64.c b/arch/x86/kernel/head64.c index 037df57a99ac..849fc9e63c2f 100644 --- a/arch/x86/kernel/head64.c +++ b/arch/x86/kernel/head64.c @@ -25,6 +25,7 @@ #include #include #include +#include static void __init zap_identity_mappings(void) { @@ -46,6 +47,7 @@ static void __init copy_bootdata(char *real_mode_data) char * command_line; memcpy(&boot_params, real_mode_data, sizeof boot_params); + sanitize_boot_params(&boot_params); if (boot_params.hdr.cmd_line_ptr) { command_line = __va(boot_params.hdr.cmd_line_ptr); memcpy(boot_command_line, command_line, COMMAND_LINE_SIZE); -- 2.20.1