omfs: sanity check cluster size

A corrupt filesystem could have a bad cluster size; this could result in
the filesystem allocating too much space for files if too large, or
getting stuck in omfs_allocate_block if too small.  The proper range is
1-8 blocks.

Reported-by: Eric Sesterhenn <snakebyte@gmx.de>
Signed-off-by: Bob Copeland <me@bobcopeland.com>

2 files changed, 7 insertions, 0 deletions

diff --git a/fs/omfs/inode.c b/fs/omfs/inode.c
index 0af5d0af9f3..579d33feddd 100644
--- a/fs/omfs/inode.c
+++ b/fs/omfs/inode.c
@@ -517,6 +517,12 @@ static int omfs_fill_super(struct super_block *sb, void *data, int silent)
                         (unsigned long long) sbi->s_num_blocks);
                 goto out_brelse_bh2;
         }
+        if (sbi->s_clustersize < 1 ||
+            sbi->s_clustersize > OMFS_MAX_CLUSTER_SIZE) {
+                printk(KERN_ERR "omfs: cluster size out of range (%d)",
+                        sbi->s_clustersize);
+                goto out_brelse_bh2;
+        }
 
         ret = omfs_get_imap(sb);
         if (ret)
diff --git a/fs/omfs/omfs_fs.h b/fs/omfs/omfs_fs.h
index 12cca245d6e..ee5e4327de9 100644
--- a/fs/omfs/omfs_fs.h
+++ b/fs/omfs/omfs_fs.h
@@ -17,6 +17,7 @@
 #define OMFS_EXTENT_CONT 0x40
 #define OMFS_XOR_COUNT 19
 #define OMFS_MAX_BLOCK_SIZE 8192
+#define OMFS_MAX_CLUSTER_SIZE 8
 
 struct omfs_super_block {
         char s_fill1[256];