Re: [PATCH 1/3] drivers: staging: wilc1000: Check for errors before kfree

Chandra Gorentla
2015-10-03T02:14:34Z

On Fri, Oct 02, 2015 at 04:39:11PM +0300, Dan Carpenter wrote:
> On Fri, Oct 02, 2015 at 06:47:35PM +0530, Chandra S Gorentla wrote:
> > During the clean-up of the function, it is need to check if
> > errors occurred, not the memory pointer.
> >
>
> The bug here is that we have a use after free on the success path. It
> should have been mentioned in the changelog.
>
> Anyway, this patch is buggy. If result == -EFAULT then it will crash.
> Also this patch is really ugly. There is someone who is going to send a
> correct fix (just add a return 0).
>
> This driver usese "do everything" style error handling. It is a bug
> prone anti-pattern because doing everything is more complicated than
> doing one thing. You can easily see it is bug prone, because it made
> you introduce a bug, right?
>
> Instead the error handling should look like this:
>
> return 0;
>
> err_free_msg:
> kfree(pstrMessage);
>
> return ret;
>
> There are no error paths where we need to free "pstrMessage->pvBuffer"
> but if we were to add one it would look like this:
>
> return 0;
>
> err_pvbuffer:
> kfree(pstrMessage->pvBuffer);
> err_msg:
> kfree(pstrMessage);
>
> return ret;
>
> This is a minimal, uncomplicated, no indenting, no if statement way of
> unwinding.
>
> regards,
> dan carpenter
>
OK. There is a problem in this patch. I will correct it, reorganize the
patch series.

Thank you,
chandra