[PATCH] Fix prefix autodetection when booting from EFI CD-ROM

[Andrey Borzenkov <arvidjaar@gmail.com>]

Fix autodetection of $prefix when booted from EFI CD-ROM.

Based on patch from Matthew Garrett, modified to not overwrite
memory returned by device path protocol handler and rebased to
current trunk.

Additionally fixes potential memory leak - dup_dp was not deallocated
if device path was not found.

Signed-off-by: Andrey Borzenkov <arvidjaar@gmail.com>

---
 grub-core/disk/efi/efidisk.c |  121 +++++++++++++++++++++++-------------------
 1 file changed, 66 insertions(+), 55 deletions(-)

diff --git a/grub-core/disk/efi/efidisk.c b/grub-core/disk/efi/efidisk.c
index 98cd226..15c8109 100644
--- a/grub-core/disk/efi/efidisk.c
+++ b/grub-core/disk/efi/efidisk.c
@@ -775,67 +775,78 @@ grub_efidisk_get_device_name (grub_efi_handle_t *handle)
   if (! ldp)
     return 0;
 
-  if (GRUB_EFI_DEVICE_PATH_TYPE (ldp) == GRUB_EFI_MEDIA_DEVICE_PATH_TYPE
-      && (GRUB_EFI_DEVICE_PATH_SUBTYPE (ldp)
-	  == GRUB_EFI_HARD_DRIVE_DEVICE_PATH_SUBTYPE))
+  if (GRUB_EFI_DEVICE_PATH_TYPE (ldp) == GRUB_EFI_MEDIA_DEVICE_PATH_TYPE)
     {
-      struct grub_efidisk_get_device_name_ctx ctx;
-      char *dev_name;
-      grub_efi_device_path_t *dup_dp, *dup_ldp;
-      grub_disk_t parent = 0;
-
-      /* It is necessary to duplicate the device path so that GRUB
-	 can overwrite it.  */
-      dup_dp = duplicate_device_path (dp);
-      if (! dup_dp)
-	return 0;
-
-      dup_ldp = find_last_device_path (dup_dp);
-      dup_ldp->type = GRUB_EFI_END_DEVICE_PATH_TYPE;
-      dup_ldp->subtype = GRUB_EFI_END_ENTIRE_DEVICE_PATH_SUBTYPE;
-      dup_ldp->length[0] = sizeof (*dup_ldp);
-      dup_ldp->length[1] = 0;
+      int is_cdrom = 0;
 
-      if (!get_diskname_from_path (dup_dp, device_name))
-	return 0;
-      parent = grub_disk_open (device_name);
-      grub_free (dup_dp);
-
-      if (! parent)
-	return 0;
-
-      /* Find a partition which matches the hard drive device path.  */
-      ctx.partition_name = NULL;
-      grub_memcpy (&ctx.hd, ldp, sizeof (ctx.hd));
-      if (ctx.hd.partition_start == 0
-	  && ctx.hd.partition_size == grub_disk_get_size (parent))
-	{
-	  dev_name = grub_strdup (parent->name);
-	}
-      else
+      switch (GRUB_EFI_DEVICE_PATH_SUBTYPE (ldp))
 	{
-	  grub_partition_iterate (parent, grub_efidisk_get_device_name_iter,
-				  &ctx);
-
-	  if (! ctx.partition_name)
+	  case GRUB_EFI_CDROM_DEVICE_PATH_SUBTYPE:
+	    is_cdrom = 1;
+	    /* Intentionally fall through */
+	  case GRUB_EFI_HARD_DRIVE_DEVICE_PATH_SUBTYPE:
 	    {
+	      struct grub_efidisk_get_device_name_ctx ctx;
+	      char *dev_name;
+	      grub_efi_device_path_t *dup_dp, *dup_ldp;
+	      grub_disk_t parent = 0;
+
+	      /* It is necessary to duplicate the device path so that GRUB
+		 can overwrite it.  */
+	      dup_dp = duplicate_device_path (dp);
+	      if (! dup_dp)
+		return 0;
+
+	      dup_ldp = find_last_device_path (dup_dp);
+	      dup_ldp->type = GRUB_EFI_END_DEVICE_PATH_TYPE;
+	      dup_ldp->subtype = GRUB_EFI_END_ENTIRE_DEVICE_PATH_SUBTYPE;
+	      dup_ldp->length[0] = sizeof (*dup_ldp);
+	      dup_ldp->length[1] = 0;
+
+	      if (!get_diskname_from_path (dup_dp, device_name))
+		{
+		  grub_free (dup_dp);
+		  return 0;
+		}
+	      grub_free (dup_dp);
+	      if (is_cdrom)
+		return grub_strdup (device_name);
+
+	      parent = grub_disk_open (device_name);
+	      if (! parent)
+		return 0;
+
+	      /* Find a partition which matches the hard drive device path.  */
+	      ctx.partition_name = NULL;
+	      grub_memcpy (&ctx.hd, ldp, sizeof (ctx.hd));
+	      if (ctx.hd.partition_start == 0
+		  && ctx.hd.partition_size == grub_disk_get_size (parent))
+		{
+		  dev_name = grub_strdup (parent->name);
+		}
+	      else
+		{
+		  grub_partition_iterate (parent, grub_efidisk_get_device_name_iter,
+					  &ctx);
+
+		  if (! ctx.partition_name)
+		    {
+		      grub_disk_close (parent);
+		      return 0;
+		    }
+
+		  dev_name = grub_xasprintf ("%s,%s", parent->name,
+					     ctx.partition_name);
+		  grub_free (ctx.partition_name);
+		}
 	      grub_disk_close (parent);
-	      return 0;
-	    }
 
-	  dev_name = grub_xasprintf ("%s,%s", parent->name,
-				     ctx.partition_name);
-	  grub_free (ctx.partition_name);
+	      return dev_name;
+	    }
 	}
-      grub_disk_close (parent);
-
-      return dev_name;
-    }
-  else
-    {
-      /* This should be an entire disk.  */
-      if (!get_diskname_from_path (dp, device_name))
-	return 0;
-      return grub_strdup (device_name);
     }
+  /* This may be guessed device - floppy, cdrom or entire disk.  */
+  if (!get_diskname_from_path (dp, device_name))
+    return 0;
+  return grub_strdup (device_name);
 }
-- 
tg: (4b9ea2e..) u/efi-cdrom-prefix (depends on: master)