From 990902e28c390217d25ea474e5ef163d79eadc7f Mon Sep 17 00:00:00 2001
From: Michael Chang <[email protected]>
Date: Fri, 31 Mar 2023 15:19:58 +0800
Subject: [PATCH 2/2] prep_loadenv: Fix regex for Open Firmware device
 specifier with encoded commas

The Open Firmware device specifier allows for comma-separated properties
of a component, but this conflicts with the way that grub separates
device and partition in its device specifier. To address this, grub
encodes commas in Open Firmware device strings with a leading backslash
as an established convention.

However, the regular expression used to extract the boot device
substring from the $cmdpath environment variable did not properly retain
commas with leading backslashes as part of the device. This could cause
the comma to be incorrectly interpreted as a partition delimiter and
result in a broken name for the boot disk.

To fix this issue, we have updated the regular expression to properly
handle the encoded comma in the Open Firmware device specifier, ensuring
that the correct boot device is identified and used.

v2:
Fix the issue of freeing an uninitialized pointer in early_prep_loadenv.

Signed-off-by: Michael Chang <[email protected]>
---
 grub-core/commands/prep_loadenv.c | 108 ++++++++++++++++++++++--------
 1 file changed, 79 insertions(+), 29 deletions(-)

--- a/grub-core/commands/prep_loadenv.c
+++ b/grub-core/commands/prep_loadenv.c
@@ -15,7 +15,7 @@
 GRUB_MOD_LICENSE ("GPLv3+");
 
 static char *
-match_substr (regmatch_t *match, const char *str)
+match_substr (const regmatch_t *match, const char *str)
 {
   if (match->rm_so != -1)
     {
@@ -185,24 +185,18 @@
   return err;
 }
 
-static grub_err_t
-boot_disk_prep_partname (char **name)
+static regmatch_t *
+regex_match_str (const char *pattern, const char *str, grub_size_t *nmatch)
 {
   regex_t regex;
   int ret;
   grub_size_t s;
   char *comperr;
-  const char *cmdpath;
   regmatch_t *matches = NULL;
   grub_err_t err = GRUB_ERR_NONE;
 
-  *name = NULL;
-
-  cmdpath = grub_env_get ("cmdpath");
-  if (!cmdpath)
-    return GRUB_ERR_NONE;
-
-  ret = regcomp (&regex, "\\(([^,]+)(,?.*)?\\)(.*)", REG_EXTENDED);
+  *nmatch = 0;
+  ret = regcomp (&regex, pattern, REG_EXTENDED);
   if (ret)
     goto fail;
 
@@ -210,22 +204,11 @@
   if (! matches)
     goto fail;
 
-  ret = regexec (&regex, cmdpath, regex.re_nsub + 1, matches, 0);
-  if (!ret)
+  ret = regexec (&regex, str, regex.re_nsub + 1, matches, 0);
+  if (ret == 0)
     {
-      char *devname = devname = match_substr (matches + 1, cmdpath);
-      if (!devname)
-	{
-	  err = grub_error (GRUB_ERR_FILE_NOT_FOUND, "%s contains no disk name", cmdpath);
-	  goto out;
-	}
-
-      err = prep_partname (devname, name);
- out:
-      grub_free (devname);
-      regfree (&regex);
-      grub_free (matches);
-      return err;
+      *nmatch = regex.re_nsub + 1;
+      return matches;
     }
 
  fail:
@@ -235,13 +218,60 @@
   if (!comperr)
     {
       regfree (&regex);
-      return grub_errno;
+      return NULL;
     }
   regerror (ret, &regex, comperr, s);
   err = grub_error (GRUB_ERR_TEST_FAILURE, "%s", comperr);
   regfree (&regex);
   grub_free (comperr);
-  return err;
+  return NULL;
+}
+
+static grub_err_t
+boot_disk_prep_partname (const char *varname, char **name)
+{
+  const char *cmdpath;
+  regmatch_t *matches;
+  grub_size_t nmatch;
+  char *devname = NULL;
+
+  *name = NULL;
+
+  if (varname)
+    cmdpath = grub_env_get (varname);
+  else
+    cmdpath = grub_env_get ("cmdpath");
+  if (!cmdpath)
+    return GRUB_ERR_NONE;
+
+  matches = regex_match_str("\\((.*)\\)(.*)", cmdpath, &nmatch);
+  if (matches && nmatch >= 2)
+    devname = match_substr (matches + 1, cmdpath);
+  if (devname == NULL)
+    goto quit;
+  grub_free (matches);
+
+  matches = regex_match_str ("(.*[^\\])(,.*)", devname, &nmatch);
+  if (matches && nmatch >= 2)
+    {
+      char *n = match_substr (matches + 1, devname);
+      grub_free (devname);
+      devname = n;
+    }
+  else
+    grub_errno = GRUB_ERR_NONE;
+  if (devname)
+    {
+      grub_printf ("search prep from disk `%s'\n", devname);
+      prep_partname (devname, name);
+    }
+
+ quit:
+  grub_free (devname);
+  grub_free (matches);
+  if (grub_errno)
+    grub_print_error ();
+  return GRUB_ERR_NONE;
 }
 
 static grub_err_t
@@ -274,13 +304,31 @@
   return GRUB_ERR_NONE;
 }
 
+static grub_err_t
+grub_cmd_prep_partname (grub_command_t cmd __attribute__ ((unused)),
+			int argc,
+			char **argv)
+{
+  char *prep = NULL;
+  const char *varname = NULL;
+
+  if (argc > 0)
+    varname = argv[0];
+
+  boot_disk_prep_partname(varname, &prep);
+  if (prep)
+    grub_printf ("prep: %s\n", prep);
+
+  return GRUB_ERR_NONE;
+}
+
 static void
 early_prep_loadenv (void)
 {
   grub_err_t err;
-  char *prep;
+  char *prep = NULL;
 
-  err = boot_disk_prep_partname (&prep);
+  err = boot_disk_prep_partname (NULL, &prep);
   if (err == GRUB_ERR_NONE && prep)
     err = prep_read_envblk (prep);
   if (err == GRUB_ERR_BAD_FILE_TYPE || err == GRUB_ERR_FILE_NOT_FOUND)
@@ -296,6 +344,10 @@
 {
   early_env_hook = early_prep_loadenv;
   cmd_prep_load =
+    grub_register_command("prep_partname", grub_cmd_prep_partname,
+			  "VARNAME",
+			  N_("Get partition name of PReP."));
+  cmd_prep_load =
     grub_register_command("prep_load_env", grub_cmd_prep_loadenv,
 			  "DEVICE",
 			  N_("Load variables from environment block file."));