Squashfs: add sanity checks to id reading at mount time
Fsfuzzer generates corrupted filesystems which throw a warn_on in
kmalloc. One of these is due to a corrupted superblock no_ids field.
Fix this by checking that the number of bytes to be read (and allocated)
does not extend into the next filesystem structure.
Also add a couple of other sanity checks of the mount-time id table
structures.
Signed-off-by: Phillip Lougher <phillip@lougher.demon.co.uk>
diff --git a/fs/squashfs/id.c b/fs/squashfs/id.c
index 2fdac67..499d08a 100644
--- a/fs/squashfs/id.c
+++ b/fs/squashfs/id.c
@@ -66,11 +66,37 @@
* 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 *table;
TRACE("In read_id_index_table, length %d\n", length);
- return squashfs_read_table(sb, id_table_start, length);
+ /* 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);
+
+ /*
+ * 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 table;
}