Re: BUG: unable to handle kernel NULL pointer dereference at 00000048

[Ryusuke Konishi <konishi.ryusuke@xxxxxxxxxxxxx>]

Hi,
On Tue, 6 Mar 2012 16:24:40 +0300, Slicky Devil wrote:
> Luckily, I seem to have been able to reproduce the bug (after
> shrinking the partition down to some hundred MB). Your patch seems to
> have fixed it!
> 
> Now I get the following, which, I think, is pretty much expected,
> since I chopped a large part of the filesystem off:
> 
> 15:52 root ~ # mount /dev/1/buggy-home test
> [  461.137823] NILFS: error searching super root.
> mount.nilfs2: Error while mounting /dev/mapper/1-buggy--home on
> /root/test: Input/output error

Hmmm.  Did you shrink the filesystem with nilfs-resize tool
before shrinking the partition ?

This error (I/O error) also looks undesirable to me.

 
> Please, fix the bug in the official kernel sources, too. Your
> filesystem proved very useful here for storing documents and other
> changeable stuff -- we don't want it get broken unexpectedly. :)

Sure, I will send the fix upstream (and stable trees).

Thanks,
Ryusuke Konishi


> Still, thanks a lot! The things you are doing here are really cool!
> 
> Cheers!
> 
> 
> 
> On Mon, Mar 5, 2012 at 5:30 PM, Ryusuke Konishi
> <konishi.ryusuke@xxxxxxxxxxxxx> wrote:
> >
> > Thank you for reporting this issue.
> >
> > I found a bug in the nilfs_load_super_block function which has
> > potential to cause this oops.
> >
> > Could you try the following patch if you still have the partition ?
> >
> >
> > Thanks,
> > Ryusuke Konishi
> >
> > diff --git a/fs/nilfs2/the_nilfs.c b/fs/nilfs2/the_nilfs.c
> > index d327140..35a8970 100644
> > --- a/fs/nilfs2/the_nilfs.c
> > +++ b/fs/nilfs2/the_nilfs.c
> > @@ -515,6 +515,7 @@ static int nilfs_load_super_block(struct the_nilfs *nilfs,
> >                brelse(sbh[1]);
> >                sbh[1] = NULL;
> >                sbp[1] = NULL;
> > +               valid[1] = 0;
> >                swp = 0;
> >        }
> >        if (!valid[swp]) {
> > --
> > 1.7.7.4
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