isofs: fix access to unallocated memory when reading corrupted filesystem

When a directory on isofs is corrupted, we did not check whether length of the
name in a directory entry and the length of the directory entry itself are
consistent.  This could lead to possible access beyond the end of buffer when
the length of the name was too big.  Add this sanity check to directory
reading code.

Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 8 insertions, 0 deletions

diff --git a/fs/isofs/dir.c b/fs/isofs/dir.c
index 1ba407c64df..2f0dc5a1463 100644
--- a/fs/isofs/dir.c
+++ b/fs/isofs/dir.c
@@ -145,6 +145,14 @@ static int do_isofs_readdir(struct inode *inode, struct file *filp,
                         }
                         de = tmpde;
                 }
+                /* Basic sanity check, whether name doesn't exceed dir entry */
+                if (de_len < de->name_len[0] +
+                                        sizeof(struct iso_directory_record)) {
+                        printk(KERN_NOTICE "iso9660: Corrupted directory entry"
+                               " in block %lu of inode %lu\n", block,
+                               inode->i_ino);
+                        return -EIO;
+                }
 
                 if (first_de) {
                         isofs_normalize_block_and_offset(de,