linux-kernel - Re: [PATCH] autofs4: Do not potentially dereference NULL pointer returned by fget() in autofs_dev_ioctl

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Date:	Mon, 24 Jan 2011 21:03:12 +0100 (CET)
From:	Jesper Juhl <jj@...osbits.net>
To:	Ian Kent <raven@...maw.net>
cc:	linux-kernel@...r.kernel.org, autofs@...ux.kernel.org
Subject: Re: [PATCH] autofs4: Do not potentially dereference NULL pointer
 returned by fget() in autofs_dev_ioctl_setpipefd()

On Mon, 24 Jan 2011, Jesper Juhl wrote:

> Hi Ian,
> 
> On Sat, 18 Dec 2010, Jesper Juhl wrote:
> 
> > Hi,
> > 
> > In fs/autofs4/dev-ioctl.c::autofs_dev_ioctl_setpipefd() we call fget(), 
> > which may return NULL, but we do not explicitly test for that NULL return 
> > so we may end up dereferencing a NULL pointer - bad.
> > 
> > When I originally submitted this patch I had chosen EBUSY as the return 
> > value to use if this happens. Ian Kent was kind enough to explain why that 
> > would most likely be wrong and why EBADF should most likely be used 
> > instead. This version of the patch uses EBADF.
> > 
> > 
> > Signed-off-by: Jesper Juhl <jj@...osbits.net>
> > ---
> >  dev-ioctl.c |    4 ++++
> >  1 file changed, 4 insertions(+)
> > 
> > diff --git a/fs/autofs4/dev-ioctl.c b/fs/autofs4/dev-ioctl.c
> > index eff9a41..a650d7e 100644
> > --- a/fs/autofs4/dev-ioctl.c
> > +++ b/fs/autofs4/dev-ioctl.c
> > @@ -372,6 +372,10 @@ static int autofs_dev_ioctl_setpipefd(struct file *fp,
> >  		return -EBUSY;
> >  	} else {
> >  		struct file *pipe = fget(pipefd);
> > +		if (!pipe) {
> > +			err = -EBADF;
> > +			goto out;
> > +		}
> >  		if (!pipe->f_op || !pipe->f_op->write) {
> >  			err = -EPIPE;
> >  			fput(pipe);
> > 
> 
> It's been more than a month now since I submitted this updated patch 
> adressing your feedback, but I've not seen any feedback on it.
> Is it OK? Will you merge it? 
> 
Ok, I need to learn to search my mailbox better. I just saw that you did 
indeed send a reply with an Acked-by: on december 28. 

Doesn't change the fact that I still need to find someone to actually 
merge it...

-- 
Jesper Juhl <jj@...osbits.net>            http://www.chaosbits.net/
Don't top-post http://www.catb.org/~esr/jargon/html/T/top-post.html
Plain text mails only, please.

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