linux-kernel - Re: Oops when using growisofs

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Message-Id: <200806230028.20643.mb@bu3sch.de>
Date:	Mon, 23 Jun 2008 00:28:20 +0200
From:	Michael Buesch <mb@...sch.de>
To:	Arnd Bergmann <arnd@...db.de>
Cc:	"linux-kernel" <linux-kernel@...r.kernel.org>,
	Jens Axboe <axboe@...nel.dk>
Subject: Re: Oops when using growisofs

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.

So, well. I dunno what i_blkbits is. There's no docs in struct inode.

-- 
Greetings Michael.
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