kern/parser: Introduce process_char() helper

grub_parser_split_cmdline() iterates over each command line character.
In order to add error checking and to simplify the subsequent error
handling, split the character processing in to a separate function.

Signed-off-by: Chris Coulson <chris.coulson@canonical.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
Patch-Name: 2021-02-security/094-kern-parser-Introduce-process_char-helper.patch

diff --git a/grub-core/kern/parser.c b/grub-core/kern/parser.c
index 39e4df65b862a03bff73808bf54f79722b0fc736..0d3582bd874b9fbd2e2d2dda189887b32ce7dc71 100644 (file)
--- a/grub-core/kern/parser.c
+++ b/grub-core/kern/parser.c
@@ -1,7 +1,7 @@
 /* parser.c - the part of the parser that can return partial tokens */
 /*
  *  GRUB  --  GRand Unified Bootloader
- *  Copyright (C) 2005,2007,2009  Free Software Foundation, Inc.
+ *  Copyright (C) 2005,2007,2009,2021  Free Software Foundation, Inc.
  *
  *  GRUB is free software: you can redistribute it and/or modify
  *  it under the terms of the GNU General Public License as published by
@@ -129,6 +129,46 @@ add_var (char *varname, char **bp, char **vp,
     *((*bp)++) = *val;
 }
 
+static grub_err_t
+process_char (char c, char *buffer, char **bp, char *varname, char **vp,
+             grub_parser_state_t state, int *argc,
+             grub_parser_state_t *newstate)
+{
+  char use;
+
+  *newstate = grub_parser_cmdline_state (state, c, &use);
+
+  /*
+   * If a variable was being processed and this character does
+   * not describe the variable anymore, write the variable to
+   * the buffer.
+   */
+  add_var (varname, bp, vp, state, *newstate);
+
+  if (check_varstate (*newstate))
+    {
+      if (use)
+       *((*vp)++) = use;
+    }
+  else if (*newstate == GRUB_PARSER_STATE_TEXT &&
+          state != GRUB_PARSER_STATE_ESC && grub_isspace (use))
+    {
+      /*
+       * Don't add more than one argument if multiple
+       * spaces are used.
+       */
+      if (*bp != buffer && *((*bp) - 1) != '\0')
+       {
+         *((*bp)++) = '\0';
+         (*argc)++;
+       }
+    }
+  else if (use)
+    *((*bp)++) = use;
+
+  return GRUB_ERR_NONE;
+}
+
 grub_err_t
 grub_parser_split_cmdline (const char *cmdline,
                           grub_reader_getline_t getline, void *getline_data,
@@ -172,35 +212,13 @@ grub_parser_split_cmdline (const char *cmdline,
       for (; *rp != '\0'; rp++)
        {
          grub_parser_state_t newstate;
-         char use;
-
-         newstate = grub_parser_cmdline_state (state, *rp, &use);
 
-         /* If a variable was being processed and this character does
-            not describe the variable anymore, write the variable to
-            the buffer.  */
-         add_var (varname, &bp, &vp, state, newstate);
-
-         if (check_varstate (newstate))
-           {
-             if (use)
-               *(vp++) = use;
-           }
-         else
+         if (process_char (*rp, buffer, &bp, varname, &vp, state, argc,
+                           &newstate) != GRUB_ERR_NONE)
            {
-             if (newstate == GRUB_PARSER_STATE_TEXT
-                 && state != GRUB_PARSER_STATE_ESC && grub_isspace (use))
-               {
-                 /* Don't add more than one argument if multiple
-                    spaces are used.  */
-                 if (bp != buffer && *(bp - 1))
-                   {
-                     *(bp++) = '\0';
-                     (*argc)++;
-                   }
-               }
-             else if (use)
-               *(bp++) = use;
+             if (rd != cmdline)
+               grub_free (rd);
+             return grub_errno;
            }
          state = newstate;
        }