linux-kernel - Re: [PATCH] misc: fastrpc: Fix double free of 'buf' in error path

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Message-ID: <ZGf+99vmXpN5nJ2f@dev-linux.lan>
Date:   Fri, 19 May 2023 15:57:59 -0700
From:   Sukrut Bellary <sukrut.bellary@...ux.com>
To:     Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
Cc:     Dan Carpenter <dan.carpenter@...aro.org>,
        Abel Vesa <abel.vesa@...aro.org>,
        Amol Maheshwari <amahesh@....qualcomm.com>,
        Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org,
        kernel-janitors@...r.kernel.org,
        Shuah Khan <skhan@...uxfoundation.org>
Subject: Re: [PATCH] misc: fastrpc: Fix double free of 'buf' in error path

On Fri, May 19, 2023 at 11:39:59AM +0100, Srinivas Kandagatla wrote:
> 
> 
> On 19/05/2023 11:22, Dan Carpenter wrote:
> > > ----------------------->cut<---------------------------
> > > diff --git a/drivers/misc/fastrpc.c b/drivers/misc/fastrpc.c
> > > index f60bbf99485c..3fdd326e1ae8 100644
> > > --- a/drivers/misc/fastrpc.c
> > > +++ b/drivers/misc/fastrpc.c
> > > @@ -1891,7 +1891,8 @@ static int fastrpc_req_mmap(struct fastrpc_user *fl,
> > > char __user *argp)
> > >                                        &args[0]);
> > >          if (err) {
> > >                  dev_err(dev, "mmap error (len 0x%08llx)\n", buf->size);
> > > -               goto err_invoke;
> > > +               fastrpc_buf_free(buf);
> > > +               return err;
> > >          }
> > > 
> > >          /* update the buffer to be able to deallocate the memory on the DSP
> > > */
> > > @@ -1930,11 +1931,7 @@ static int fastrpc_req_mmap(struct fastrpc_user *fl,
> > > char __user *argp)
> > >          return 0;
> > > 
> > >   err_assign:
> > > -       fastrpc_req_munmap_impl(fl, buf);
> > > -err_invoke:
> > > -       fastrpc_buf_free(buf);
> > > -
> > > -       return err;
> > > +       return fastrpc_req_munmap_impl(fl, buf);
> > 
> > This will return success if copy_to_user() fails.
> > 
> that is true, using return value of fastrpc_req_munmap_impl does not really
> make sense here we should just return err in either case to the user.
>

Thanks, Srini and Dan, for reviewing the patch and suggestions.
I will add this in v2.

Regards,
Sukrut Bellary

> --srini
> 
> > regards,
> > dan carpenter
> >