linux-kernel - Re: Oops when using growisofs

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Message-Id: <200806231659.07437.nickpiggin@yahoo.com.au>
Date:	Mon, 23 Jun 2008 16:59:07 +1000
From:	Nick Piggin <nickpiggin@...oo.com.au>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Michael Buesch <mb@...sch.de>, Arnd Bergmann <arnd@...db.de>,
	"linux-kernel" <linux-kernel@...r.kernel.org>,
	Jens Axboe <axboe@...nel.dk>, Jan Kara <jack@....cz>
Subject: Re: Oops when using growisofs

On Monday 23 June 2008 16:34, Andrew Morton wrote:
> On Mon, 23 Jun 2008 00:28:20 +0200 Michael Buesch <mb@...sch.de> wrote:
> > On Monday 23 June 2008 00:05:51 Michael Buesch wrote:
> > > > Note: r9 and r3 are both NULL pointers. r3 is the value returned from
> > > > alloc_page_buffers. R9 is a copy of that, which gets accessed.
> > >
> > > Hm, yeah. I looked at that code already, but I can't see how it could
> > > return a NULL pointer.
> >
> > Well, actually, it can return a NULL pointer.
> >
> >  928         head = NULL;
> >  929         offset = PAGE_SIZE;
> >  930         while ((offset -= size) >= 0) {
> > ...
> >  949         }
> >  950         return head;
> >
> > So if size, which is a passed in as parameter, is > PAGE_SIZE it will
> > return NULL.
> >
> > The size parameter is calculated by doing
> > blocksize = 1 << inode->i_blkbits;
> > in an earlier function in the callchain.
>
> Yes, that's a more likely scenario.  isofs has a history of passing
> garbage into the VFS.

Yes isofs will pass in a too-big page here (IIRC 32K or something).
And trigger this oops.
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