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

[Srinivas Kandagatla <srinivas.kandagatla@xxxxxxxxxx>]

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.

--srini

> regards,
> dan carpenter