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

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Date:	Tue, 02 Sep 2008 13:04:58 -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

Resubmitting my previous 9p bug fix patch that removes the bogus return
value in p9_put_data which made every p9_client_write fail. 

Signed-off-by: Abhishek Kulkarni <kulkarni@...l.gov>
---
 net/9p/conv.c |   12 +++---------
 1 files changed, 3 insertions(+), 9 deletions(-)

diff --git a/net/9p/conv.c b/net/9p/conv.c
index 4454720..08ec35a 100644
--- a/net/9p/conv.c
+++ b/net/9p/conv.c
@@ -446,13 +446,12 @@ p9_put_str(struct cbuf *bufp, char *data, struct
p9_str *str)
        }
 }

-static int
+static void
 p9_put_data(struct cbuf *bufp, const char *data, int count,
                   unsigned char **pdata)
 {
        *pdata = buf_alloc(bufp, count);
        memmove(*pdata, data, count);
-       return count;
 }

 static int
@@ -851,7 +850,7 @@ EXPORT_SYMBOL(p9_create_tread);
 struct p9_fcall *p9_create_twrite(u32 fid, u64 offset, u32 count,
                                      const char *data)
 {
-       int size, err;
+       int size;
        struct p9_fcall *fc;
        struct cbuf buffer;
        struct cbuf *bufp = &buffer;
@@ -865,12 +864,7 @@ struct p9_fcall *p9_create_twrite(u32 fid, u64
offset, u32 count,
        p9_put_int32(bufp, fid, &fc->params.twrite.fid);
        p9_put_int64(bufp, offset, &fc->params.twrite.offset);
        p9_put_int32(bufp, count, &fc->params.twrite.count);
-       err = p9_put_data(bufp, data, count, &fc->params.twrite.data);
-       if (err) {
-               kfree(fc);
-               fc = ERR_PTR(err);
-               goto error;
-       }
+       p9_put_data(bufp, data, count, &fc->params.twrite.data);

        if (buf_check_overflow(bufp)) {
                kfree(fc);
--
1.5.4.3



On Thu, 2008-08-28 at 12:35 -0600, Abhishek Kulkarni wrote:
> 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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