linux-kernel - Re: pipe

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Message-ID: <CA+55aFzdPaFQROzFhz-v1Qn=3aDP=4uGTiOJxR26cR91uJHxyg@mail.gmail.com>
Date:	Thu, 7 Mar 2013 16:21:13 -0800
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Dave Jones <davej@...hat.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	Al Viro <viro@...iv.linux.org.uk>
Subject: Re: pipe_release oops.

On Thu, Mar 7, 2013 at 2:36 PM, Dave Jones <davej@...hat.com> wrote:
>
> The hits keep on coming..
>
> [  255.609172] BUG: unable to handle kernel NULL pointer dereference at 0000000000000064
> [  255.610393] IP: [<ffffffff811bad62>] pipe_release+0x42/0xd0

Ok, I think this is the same issue as your fasync thing.

So add a "if (pipe) { }" in pipe_release() too.

It's a bit odd, becuse we always allocate an inode->i_pipe whenever we
associate the file with any of the pipe operations, so I don't see how
that NULL i_pipe happens. But we do have that "free_pipe_info() if
there are no readers or writers" logic and I bet that's what triggers
this somehow. I just don't see what the exact sequence is.

                    Linus
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