ext3 updates for 2.4.20

There are three patches at

	http://www.zip.com.au/~akpm/linux/patches/2.4/2.4.20/

sync_fs.patch:
Fix the ext3 data=journal data-loss-on-unmount bug

sync_fs-fix.patch:
Fix sync_fs.patch to not deadlock the fs when running `mount -o remount' against a heavily loaded filesystem.

ext3-use-after-free.patch
Fix a use-after-free bug which can cause memory corruption if the filesystem runs out of space, or runs out of free inodes.

Instructions for downloading and applying these patches are at

	http://www.zip.com.au/~akpm/linux/ext3/

Hmmm, this took me a while to find the first time around in the commit_super code, and I almost forgot about it.

Looking at the loop in sync_supers()

       while (sb != sb_entry(&super_blocks))
                if (sb->s_dirt) {
                        sb->s_count++;
                        spin_unlock(&sb_lock);

Right here, we can race against kill_super, which means an unmount can make the FS go away completely. The only thing that saves the write_super() call is a check for s->s_root != NULL. Since we don't check that before calling sync_fs, it should race against an unmount.

                        down_read(&sb->s_umount);
                        write_super(sb);
                        if (wait && sb->s_op && sb->s_op->sync_fs)
                                sb->s_op->sync_fs(sb);
                        drop_super(sb);
                        goto restart;
                } else

Any reason ext3 can't have a check for s_root in there?

-chris