diff --git a/fs/jbd/journal.c b/fs/jbd/journal.c
index 5d14243..6ad18ba 100644
--- a/fs/jbd/journal.c
+++ b/fs/jbd/journal.c
@@ -1030,6 +1030,14 @@ static int journal_get_superblock(journal_t *journal)
 		goto out;
 	}
 
+	if (be32_to_cpu(sb->s_first) == 0 ||
+	    be32_to_cpu(sb->s_first) >= journal->j_maxlen) {
+		printk(KERN_WARNING
+			"JBD: Invalid start block of journal: %u\n",
+			be32_to_cpu(sb->s_first));
+		goto out;
+	}
+
 	return 0;
 
 out:
diff --git a/fs/jbd2/journal.c b/fs/jbd2/journal.c
index 6ddc553..33eb17c 100644
--- a/fs/jbd2/journal.c
+++ b/fs/jbd2/journal.c
@@ -1029,6 +1029,14 @@ static int journal_get_superblock(journal_t *journal)
 		goto out;
 	}
 
+	if (be32_to_cpu(sb->s_first) == 0 ||
+	    be32_to_cpu(sb->s_first) >= journal->j_maxlen) {
+		printk(KERN_WARNING
+			"JBD2: Invalid start block of journal: %u\n",
+			be32_to_cpu(sb->s_first));
+		goto out;
+	}
+
 	return 0;
 
 out: