Commit 5dcd14ec authored by H. Peter Anvin's avatar H. Peter Anvin
Browse files

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: default avatarYinghai Lu <yinghai@kernel.org>
Link: http://lkml.kernel.org/r/1359058816-7615-26-git-send-email-yinghai@kernel.org


Signed-off-by: default avatarH. Peter Anvin <hpa@linux.intel.com>
parent 09c205af

arch/x86/boot/compressed/misc.c

+2 −0
Original line number Diff line number Diff line
@@ -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;

arch/x86/boot/compressed/misc.h

+1 −0
Original line number Diff line number Diff line
@@ -18,6 +18,7 @@ 
#include <asm/page.h>

#include <asm/boot.h>

#include <asm/bootparam.h>

#include <asm/bootparam_utils.h>



#define BOOT_BOOT_H

#include "../ctype.h"

arch/x86/include/asm/bootparam_utils.h

0 → 100644
+38 −0
Original line number Diff line number Diff line 
#ifndef _ASM_X86_BOOTPARAM_UTILS_H

#define _ASM_X86_BOOTPARAM_UTILS_H



#include <asm/bootparam.h>



/*

 * 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 */

arch/x86/kernel/head32.c

+3 −0
Original line number Diff line number Diff line
@@ -18,6 +18,7 @@ 
#include <asm/io_apic.h>

#include <asm/bios_ebda.h>

#include <asm/tlbflush.h>

#include <asm/bootparam_utils.h>



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));

arch/x86/kernel/head64.c

+2 −0
Original line number Diff line number Diff line
@@ -25,6 +25,7 @@ 
#include <asm/kdebug.h>

#include <asm/e820.h>

#include <asm/bios_ebda.h>

#include <asm/bootparam_utils.h>



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);

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