linux-kernel - Re: [PATCH net] ice: Fix freeing uninitialized pointers

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Message-ID: <82b49991-eb5a-7e8c-67e0-b0fd932f40b4@inria.fr>
Date: Fri, 22 Mar 2024 03:24:56 -0400 (EDT)
From: Julia Lawall <julia.lawall@...ia.fr>
To: Jakub Kicinski <kuba@...nel.org>
cc: Jesse Brandeburg <jesse.brandeburg@...el.com>, 
    Julia Lawall <Julia.Lawall@...ia.fr>, 
    Andy Shevchenko <andriy.shevchenko@...ux.intel.com>, 
    Dan Carpenter <dan.carpenter@...aro.org>, kernel-janitors@...r.kernel.org, 
    netdev@...r.kernel.org, intel-wired-lan@...ts.osuosl.org, 
    Maciej Fijalkowski <maciej.fijalkowski@...el.com>, 
    Przemek Kitszel <przemyslaw.kitszel@...el.com>, 
    Tony Nguyen <anthony.l.nguyen@...el.com>, 
    LKML <linux-kernel@...r.kernel.org>, 
    Alexander Lobakin <aleksander.lobakin@...el.com>, 
    David Laight <David.Laight@...lab.com>, 
    "David S. Miller" <davem@...emloft.net>, 
    Eric Dumazet <edumazet@...gle.com>, Jiri Pirko <jiri@...nulli.us>, 
    Jonathan Cameron <jic23@...nel.org>, Kees Cook <keescook@...omium.org>, 
    Lukasz Czapnik <lukasz.czapnik@...el.com>, Paolo Abeni <pabeni@...hat.com>, 
    Pucha Himasekhar Reddy <himasekharx.reddy.pucha@...el.com>, 
    Dan Williams <dan.j.williams@...el.com>
Subject: Re: [PATCH net] ice: Fix freeing uninitialized pointers



On Thu, 21 Mar 2024, Jakub Kicinski wrote:

> On Thu, 21 Mar 2024 15:27:47 -0700 Jesse Brandeburg wrote:
> > The gist of it is that we should instead be using inline declarations,
> > which I also agree is a reasonable style for this. It more clearly shows
> > the __free(kfree) and the allocation (kzalloc, kcalloc, etc) on the same
> > (or virtually the same) line of code.
> >
> > I'm curious if Jakub would dislike this less? Accept?
>
> At present I find this construct unreadable.
> I may get used to it, hard to say.
>
> Also I don't see the benefit of the auto-freeing construct,
> I'd venture a guess that all the bugs it may prevent would
> have been caught by smatch. But I'm an old curmudgeon stuck
> in my ways. Feel free to experiment in Intel drivers, and we'll
> see how it works out 🤷️

In my experiments with of_node_put, there seem to be many functions where
removing the frees makes the function much more readable.  But
kmalloc/kfree may be used in different contexts, where the management of
the memory is a smaller percentage of the overall code.  So the tradeoffs
may be different.

julia