[PATCH 5.2 128/162] x86/boot: Save fields explicitly, zero out everything else

Greg Kroah-Hartman
2019-08-27T08:05:29Z

From: John Hubbard <jhubbard@nvidia.com>

commit a90118c445cc7f07781de26a9684d4ec58bfcfd1 upstream.

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: Thomas Gleixner <tglx@linutronix.de>
Suggested-by: H. Peter Anvin <hpa@zytor.com>
Signed-off-by: John Hubbard <jhubbard@nvidia.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/20190731054627.5627-2-jhubbard@nvidia.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
arch/x86/include/asm/bootparam_utils.h | 63 +++++++++++++++++++++++++--------
1 file changed, 48 insertions(+), 15 deletions(-)

--- a/arch/x86/include/asm/bootparam_utils.h
+++ b/arch/x86/include/asm/bootparam_utils.h
@@ -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
* 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));
}
}