[SECURITY PATCH 113/117] kern/misc: Add STRING type for internal printf() format handling

[Daniel Kiper]

From: Thomas Frauendorfer | Miray Software <tf@miray.de>

Set printf() argument type for "%s" to new type STRING. This is in
preparation for a follow up patch to compare a printf() format string
against an expected printf() format string.

For "%s" the corresponding printf() argument is dereferenced as pointer
while all other argument types are defined as integer value. However,
when validating a printf() format it is necessary to differentiate "%s"
from "%p" and other integers. So, let's do that.

Signed-off-by: Thomas Frauendorfer | Miray Software <tf@miray.de>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
---
 grub-core/kern/misc.c | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/grub-core/kern/misc.c b/grub-core/kern/misc.c
index c58857ca2..074728b2b 100644
--- a/grub-core/kern/misc.c
+++ b/grub-core/kern/misc.c
@@ -33,7 +33,8 @@ union printf_arg
   enum
     {
       INT, LONG, LONGLONG,
-      UNSIGNED_INT = 3, UNSIGNED_LONG, UNSIGNED_LONGLONG
+      UNSIGNED_INT = 3, UNSIGNED_LONG, UNSIGNED_LONGLONG,
+      STRING
     } type;
   long long ll;
 };
@@ -791,12 +792,14 @@ parse_printf_arg_fmt (const char *fmt0, struct 
printf_args *args)
          args->ptr[curn].type = INT + longfmt;
          break;
        case 'p':
-       case 's':
          if (sizeof (void *) == sizeof (long long))
            args->ptr[curn].type = UNSIGNED_LONGLONG;
          else
            args->ptr[curn].type = UNSIGNED_INT;
          break;
+       case 's':
+         args->ptr[curn].type = STRING;
+         break;
        case 'C':
        case 'c':
          args->ptr[curn].type = INT;
@@ -831,6 +834,12 @@ parse_printf_args (const char *fmt0, struct printf_args 
*args, va_list args_in)
       case UNSIGNED_LONGLONG:
        args->ptr[n].ll = va_arg (args_in, long long);
        break;
+      case STRING:
+       if (sizeof (void *) == sizeof (long long))
+         args->ptr[n].ll = va_arg (args_in, long long);
+       else
+         args->ptr[n].ll = va_arg (args_in, unsigned int);
+       break;
       }
 }
 
-- 
2.11.0