1 files changed, 26 insertions, 16 deletions

diff --git a/fs/squashfs/id.c b/fs/squashfs/id.c
index d8f32452638e..a70858e0fb44 100644
--- a/fs/squashfs/id.c
+++ b/fs/squashfs/id.c
@@ -2,7 +2,7 @@
  * Squashfs - a compressed read only filesystem for Linux
  *
  * Copyright (c) 2002, 2003, 2004, 2005, 2006, 2007, 2008
- * Phillip Lougher <phillip@lougher.demon.co.uk>
+ * Phillip Lougher <phillip@squashfs.org.uk>
  *
  * This program is free software; you can redistribute it and/or
  * modify it under the terms of the GNU General Public License
@@ -66,27 +66,37 @@ int squashfs_get_id(struct super_block *sb, unsigned int index,
  * Read uncompressed id lookup table indexes from disk into memory
  */
 __le64 *squashfs_read_id_index_table(struct super_block *sb,
-			u64 id_table_start, unsigned short no_ids)
+		u64 id_table_start, u64 next_table, unsigned short no_ids)
 {
 	unsigned int length = SQUASHFS_ID_BLOCK_BYTES(no_ids);
-	__le64 *id_table;
-	int err;
+	__le64 *table;
 
 	TRACE("In read_id_index_table, length %d\n", length);
 
-	/* Allocate id lookup table indexes */
-	id_table = kmalloc(length, GFP_KERNEL);
-	if (id_table == NULL) {
-		ERROR("Failed to allocate id index table\n");
-		return ERR_PTR(-ENOMEM);
-	}
+	/* Sanity check values */
+
+	/* there should always be at least one id */
+	if (no_ids == 0)
+		return ERR_PTR(-EINVAL);
+
+	/*
+	 * length bytes should not extend into the next table - this check
+	 * also traps instances where id_table_start is incorrectly larger
+	 * than the next table start
+	 */
+	if (id_table_start + length > next_table)
+		return ERR_PTR(-EINVAL);
+
+	table = squashfs_read_table(sb, id_table_start, length);
 
-	err = squashfs_read_table(sb, id_table, id_table_start, length);
-	if (err < 0) {
-		ERROR("unable to read id index table\n");
-		kfree(id_table);
-		return ERR_PTR(err);
+	/*
+	 * table[0] points to the first id lookup table metadata block, this
+	 * should be less than id_table_start
+	 */
+	if (!IS_ERR(table) && table[0] >= id_table_start) {
+		kfree(table);
+		return ERR_PTR(-EINVAL);
 	}
 
-	return id_table;
+	return table;
 }