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Commit a90118c4 authored by John Hubbard's avatar John Hubbard Committed by Thomas Gleixner
Browse files

x86/boot: Save fields explicitly, zero out everything else 



Recent gcc compilers (gcc 9.1) generate warnings about an out of bounds
memset, if the memset goes accross several fields of a struct. This
generated a couple of warnings on x86_64 builds in sanitize_boot_params().

Fix this by explicitly saving the fields in struct boot_params
that are intended to be preserved, and zeroing all the rest.

[ tglx: Tagged for stable as it breaks the warning free build there as well ]

Suggested-by: default avatarThomas Gleixner <tglx@linutronix.de>
Suggested-by: default avatarH. Peter Anvin <hpa@zytor.com>
Signed-off-by: default avatarJohn Hubbard <jhubbard@nvidia.com>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/20190731054627.5627-2-jhubbard@nvidia.com
parent 5ed1c835

arch/x86/include/asm/bootparam_utils.h

+48 −15
Original line number Diff line number Diff line
@@ -18,6 +18,20 @@ 
 * Note: efi_info is commonly left uninitialized, but that field has a

 * private magic, so it is better to leave it unchanged.

 */



#define sizeof_mbr(type, member) ({ sizeof(((type *)0)->member); })



#define BOOT_PARAM_PRESERVE(struct_member)				\

	{								\

		.start = offsetof(struct boot_params, struct_member),	\

		.len   = sizeof_mbr(struct boot_params, struct_member),	\

	}



struct boot_params_to_save {

	unsigned int start;

	unsigned int len;

};



static void sanitize_boot_params(struct boot_params *boot_params)

{

	/*
@@ -35,21 +49,40 @@ static void sanitize_boot_params(struct boot_params *boot_params) 
	 * problems again.

	 */

	if (boot_params->sentinel) {

		/* fields in boot_params are left uninitialized, clear them */

		boot_params->acpi_rsdp_addr = 0;

		memset(&boot_params->ext_ramdisk_image, 0,

		       (char *)&boot_params->efi_info -

			(char *)&boot_params->ext_ramdisk_image);

		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));

		static struct boot_params scratch;

		char *bp_base = (char *)boot_params;

		char *save_base = (char *)&scratch;

		int i;



		const struct boot_params_to_save to_save[] = {

			BOOT_PARAM_PRESERVE(screen_info),

			BOOT_PARAM_PRESERVE(apm_bios_info),

			BOOT_PARAM_PRESERVE(tboot_addr),

			BOOT_PARAM_PRESERVE(ist_info),

			BOOT_PARAM_PRESERVE(acpi_rsdp_addr),

			BOOT_PARAM_PRESERVE(hd0_info),

			BOOT_PARAM_PRESERVE(hd1_info),

			BOOT_PARAM_PRESERVE(sys_desc_table),

			BOOT_PARAM_PRESERVE(olpc_ofw_header),

			BOOT_PARAM_PRESERVE(efi_info),

			BOOT_PARAM_PRESERVE(alt_mem_k),

			BOOT_PARAM_PRESERVE(scratch),

			BOOT_PARAM_PRESERVE(e820_entries),

			BOOT_PARAM_PRESERVE(eddbuf_entries),

			BOOT_PARAM_PRESERVE(edd_mbr_sig_buf_entries),

			BOOT_PARAM_PRESERVE(edd_mbr_sig_buffer),

			BOOT_PARAM_PRESERVE(e820_table),

			BOOT_PARAM_PRESERVE(eddbuf),

		};



		memset(&scratch, 0, sizeof(scratch));



		for (i = 0; i < ARRAY_SIZE(to_save); i++) {

			memcpy(save_base + to_save[i].start,

			       bp_base + to_save[i].start, to_save[i].len);

		}



		memcpy(boot_params, save_base, sizeof(*boot_params));

	}

}