linux-kernel - Re: Kernel 3.1.0-rc4 oops when connecting iPod

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Date:	Sat, 3 Sep 2011 07:57:23 +0100 (BST)
From:	Hin-Tak Leung <hintak_leung@...oo.co.uk>
To:	Pavel Ivanov <paivanof@...il.com>
Cc:	linux-fsdevel@...r.kernel.org,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: Kernel 3.1.0-rc4 oops when connecting iPod

--- On Sat, 3/9/11, Pavel Ivanov <paivanof@...il.com> wrote:

> On Fri, Sep 2, 2011 at 11:59 PM,
> Hin-Tak Leung <hintak_leung@...oo.co.uk>
> wrote:
> >> With kernel 3.1.0-rc4 any attempt to connect iPod
> to USB
> >> leads to
> >> kernel oops. I'd say that stacktrace of the oops
> is pretty
> >> much random
> >> and not related to HFS. But I was able to get
> useful info
> >> from it when
> >> I recompiled with CONFIG_SLUB_DEBUG_ON=y. In this
> case I
> >> don't get
> >> oops but the following instead:
> >
> > There are a few hfsplus related changes to do
> protection against invalid data like this, but may be there
> are more. It would be useful to have the output from your
> > objdump -l -d hfsplus.ko | grep  -A 1000
> '<hfsplus_fill_super>'
> > (the -l gives line numbers against the kernel tree, so
> would be useful if you run this against the ko there...)
> 
> Output of this command is in attachment.

That's interesting. You said "hfs: filesystem size too large." always appears twice (with kernel 3.1-rc4) before it oops. And in your 2.6.38.11 kernel, you had "hfs: unable to find HFS+ superblock" twice.

The oops place is the "kfree(sbi->s_backup_vhdr)" in line 529 in fs/hfsplus/super.c:

527: out_free_vhdr:
528:        kfree(sbi->s_vhdr);
529:        kfree(sbi->s_backup_vhdr);

It would appear the s_backup_vhdr is somehow garbage but that was not caught in the 3.1-rc4 version of hfsplus_read_wrapper() ; it was caught by the 2.6.38.11 version of hfsplus_read_wrapper(). hfsplus_read_wrapper() was changed in the 2.6.39/3.0 time frame by this:

    commit 52399b171dfaea02b6944cd6feba49b624147126
    Author: Christoph Hellwig <hch@...era.com>
    Date:   Tue Nov 23 14:37:47 2010 +0100
    
        hfsplus: use raw bio access for the volume headers

That's code I don't quite understand (I worked on the hfsplus journal code recently, supposedly mentoring for that GSoC project).

If you are happy enough to do a bit of experimenting, can you try putting a 
"if(sbi->s_backup_vhdr)" before line 529?

Also it is curious why it wasn't caught in wrapper.c arond 229 to 236 ending with:
"if (sbi->s_backup_vhdr->signature != sbi->s_vhdr->signature)"


The file system too large comes from line 402 in super.c:
-----------------------
        err = generic_check_addressable(sbi->alloc_blksz_shift,
                                        sbi->total_blocks);
        if (err) {
                printk(KERN_ERR "hfs: filesystem size too large.\n");
                goto out_free_vhdr;

-----------------------
So it might be interesting to see what is too large... try changing that to:

printk(KERN_ERR "hfs: filesystem size too large blksz_shift=%d, total_blocks=%d\n", sbi->alloc_blksz_shift, sbi->total_blocks);

?

It is a 42GB image - if it were smaller I would suggest dd'ing that and upload it somewhere to check...



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