Squashfs: add sanity checks to fragment reading at mount time
Fsfuzzer generates corrupted filesystems which throw a warn_on in
kmalloc. One of these is due to a corrupted superblock fragments 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 fragment table
structures.
Signed-off-by: Phillip Lougher <phillip@lougher.demon.co.uk>
diff --git a/fs/squashfs/fragment.c b/fs/squashfs/fragment.c
index 567093d..bfd7075 100644
--- a/fs/squashfs/fragment.c
+++ b/fs/squashfs/fragment.c
@@ -71,9 +71,29 @@
* Read the uncompressed fragment lookup table indexes off disk into memory
*/
__le64 *squashfs_read_fragment_index_table(struct super_block *sb,
- u64 fragment_table_start, unsigned int fragments)
+ u64 fragment_table_start, u64 next_table, unsigned int fragments)
{
unsigned int length = SQUASHFS_FRAGMENT_INDEX_BYTES(fragments);
+ __le64 *table;
- return squashfs_read_table(sb, fragment_table_start, length);
+ /*
+ * Sanity check, length bytes should not extend into the next table -
+ * this check also traps instances where fragment_table_start is
+ * incorrectly larger than the next table start
+ */
+ if (fragment_table_start + length > next_table)
+ return ERR_PTR(-EINVAL);
+
+ table = squashfs_read_table(sb, fragment_table_start, length);
+
+ /*
+ * table[0] points to the first fragment table metadata block, this
+ * should be less than fragment_table_start
+ */
+ if (!IS_ERR(table) && table[0] >= fragment_table_start) {
+ kfree(table);
+ return ERR_PTR(-EINVAL);
+ }
+
+ return table;
}
diff --git a/fs/squashfs/squashfs.h b/fs/squashfs/squashfs.h
index 3b705f1..647b81b 100644
--- a/fs/squashfs/squashfs.h
+++ b/fs/squashfs/squashfs.h
@@ -57,7 +57,7 @@
/* fragment.c */
extern int squashfs_frag_lookup(struct super_block *, unsigned int, u64 *);
extern __le64 *squashfs_read_fragment_index_table(struct super_block *,
- u64, unsigned int);
+ u64, u64, unsigned int);
/* id.c */
extern int squashfs_get_id(struct super_block *, unsigned int, unsigned int *);
diff --git a/fs/squashfs/super.c b/fs/squashfs/super.c
index 80a7119..efa8118 100644
--- a/fs/squashfs/super.c
+++ b/fs/squashfs/super.c
@@ -261,6 +261,7 @@
msblk->inode_lookup_table = NULL;
goto failed_mount;
}
+ next_table = msblk->inode_lookup_table[0];
sb->s_export_op = &squashfs_export_ops;
@@ -278,7 +279,7 @@
/* Allocate and read fragment index table */
msblk->fragment_index = squashfs_read_fragment_index_table(sb,
- le64_to_cpu(sblk->fragment_table_start), fragments);
+ le64_to_cpu(sblk->fragment_table_start), next_table, fragments);
if (IS_ERR(msblk->fragment_index)) {
ERROR("unable to read fragment index table\n");
err = PTR_ERR(msblk->fragment_index);