svn commit: r339802 - head/stand/efi/loader

[Warner Losh]

Author: imp
Date: Fri Oct 26 23:44:50 2018
New Revision: 339802
URL: https://svnweb.freebsd.org/changeset/base/339802

Log:
  Fix pointer arithmetic
  
  Pointer math to find the size in bytes only works with char types.
  Use correct pointer math to determine if we have enough of a header to
  look at or not.
  
  MFC After: 3 days
  X-MFX-With: r339800
  Noticed by: jhb@
  Sponsored by: Netflix, Inc

Modified:
  head/stand/efi/loader/main.c

Modified: head/stand/efi/loader/main.c
==============================================================================
--- head/stand/efi/loader/main.c	Fri Oct 26 23:44:39 2018	(r339801)
+++ head/stand/efi/loader/main.c	Fri Oct 26 23:44:50 2018	(r339802)
@@ -298,6 +298,8 @@ fix_dosisms(char *p)
 	}
 }
 
+#define SIZE(dp, edp) (size_t)((intptr_t)(void *)edp - (intptr_t)(void *)dp)
+
 enum { BOOT_INFO_OK = 0, BAD_CHOICE = 1, NOT_SPECIFIC = 2  };
 static int
 match_boot_info(EFI_LOADED_IMAGE *img __unused, char *boot_info, size_t bisz)
@@ -349,7 +351,7 @@ match_boot_info(EFI_LOADED_IMAGE *img __unused, char *
 	edp = (EFI_DEVICE_PATH *)(walker + fplen);
 	if ((char *)edp > ep)
 		return NOT_SPECIFIC;
-	while (dp < edp && (size_t)(edp - dp) > sizeof(EFI_DEVICE_PATH)) {
+	while (dp < edp && SIZE(dp, edp) > sizeof(EFI_DEVICE_PATH)) {
 		text = efi_devpath_name(dp);
 		if (text != NULL) {
 			printf("   BootInfo Path: %S\n", text);