linux-kernel - Re: [PATCH] 9p bug fix: return non-zero error value in p9_put

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Message-Id: <1219948516.2678.16.camel@blender>
Date:	Thu, 28 Aug 2008 12:35:16 -0600
From:	Abhishek Kulkarni <kulkarni@...l.gov>
To:	Eric Van Hensbergen <ericvh@...il.com>
Cc:	v9fs-developer@...ts.sourceforge.net, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] 9p bug fix: return non-zero error value in p9_put_data

On Thu, 2008-08-28 at 11:10 -0700, Eric Van Hensbergen wrote:
> On Tue, Aug 26, 2008 at 10:30 AM, Abhishek Kulkarni <kulkarni@...l.gov> wrote:
> > p9_put_data is called by p9_create_twrite which expects it to return a
> > non-zero value on error. This was the reason why every p9_client_write
> > was failing. This patch also adds a check for buffer overflow in
> > p9_put_data.
> >
> 
> I'm a bit confused about when this is even getting called -- O thought
> all writes were following the p9_client_uwrite path?

Yes, this bug didn't come up to the surface since p9_create_twrite is
not even being called anywhere in v9fs. I tripped over it when using 9p
for a different module that I am working on. 

> 
> Also, we do the bufoverflow check in p9_create_write -- so with your
> patch aren't we doing this twice?
> 
Yes, but then that makes the "check for error in return value" in
p9_create_twrite useless since memmove is not going to return an error
in any case.

Going with the existing convention however, I think the bufoverflow
check is unnecessary in p9_put_data and so is the check for error on
return.

I'll resubmit a patch.

 -- Abhishek


>            -eric
> 
> 
> > Signed-off-by: Abhishek Kulkarni <kulkarni@...l.gov>
> > ---
> >  net/9p/conv.c |    5 ++++-
> >  1 files changed, 4 insertions(+), 1 deletions(-)
> > diff --git a/net/9p/conv.c b/net/9p/conv.c
> > index 4454720..7f6db15 100644
> > --- a/net/9p/conv.c
> > +++ b/net/9p/conv.c
> > @@ -451,8 +451,11 @@ p9_put_data(struct cbuf *bufp, const char *data,
> > int count,
> >                   unsigned char **pdata)
> >  {
> >        *pdata = buf_alloc(bufp, count);
> > +       if (buf_check_overflow(bufp))
> > +               return -EIO;
> > +
> >        memmove(*pdata, data, count);
> > -       return count;
> > +       return 0;
> >  }
> >
> >  static int
> >
> >
> > Thanks,
> >  -- Abhishek
> >
> >

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