Squashfs: add sanity checks to lookup table reading at mount time

Fsfuzzer generates corrupted filesystems which throw a warn_on in
kmalloc.  One of these is due to a corrupted superblock inodes 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 lookup table
structures.

Signed-off-by: Phillip Lougher <phillip@lougher.demon.co.uk>

1 files changed, 2 insertions, 1 deletions

diff --git a/fs/squashfs/super.c b/fs/squashfs/super.c
index 8f5f2781a60e..80a7119870a6 100644
--- a/fs/squashfs/super.c
+++ b/fs/squashfs/super.c
@@ -245,6 +245,7 @@ allocate_id_index_table:
                 msblk->id_table = NULL;
                 goto failed_mount;
         }
+        next_table = msblk->id_table[0];
 
         /* Handle inode lookup table */
         lookup_table_start = le64_to_cpu(sblk->lookup_table_start);
@@ -253,7 +254,7 @@ allocate_id_index_table:
 
         /* Allocate and read inode lookup table */
         msblk->inode_lookup_table = squashfs_read_inode_lookup_table(sb,
-                lookup_table_start, msblk->inodes);
+                lookup_table_start, next_table, msblk->inodes);
         if (IS_ERR(msblk->inode_lookup_table)) {
                 ERROR("unable to read inode lookup table\n");
                 err = PTR_ERR(msblk->inode_lookup_table);