Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::3:7 as permitted sender) client-ip=2620:137:e000::3:7;
Date:   Sat, 18 Nov 2023 14:42:44 +0100
From:   Florian Westphal <fw@strlen.de>
To:     Kamil Duljas <kamil.duljas@gmail.com>
Cc:     Florian Westphal <fw@strlen.de>, Jakub Kicinski <kuba@kernel.org>,
        "David S . Miller" <davem@davemloft.net>,
        Eric Dumazet <edumazet@google.com>,
        Paolo Abeni <pabeni@redhat.com>, Jiri Pirko <jiri@resnulli.us>,
        Johannes Berg <johannes@sipsolutions.net>,
        netdev@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] genetlink: Prevent memory leak when krealloc fail
Message-ID: <20231118134244.GB30289@breakpoint.cc>
References: <20231118113357.1999-1-kamil.duljas@gmail.com>
 <20231118120235.GA30289@breakpoint.cc>
 <CAFR=A7nkyx_Lf=p0BS-S68_vxQL97rUoLMZpo4kxHjKykAgTRw@mail.gmail.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <CAFR=A7nkyx_Lf=p0BS-S68_vxQL97rUoLMZpo4kxHjKykAgTRw@mail.gmail.com>
User-Agent: Mutt/1.10.1 (2018-07-13)
Precedence: bulk

Kamil Duljas <kamil.duljas@gmail.com> wrote:
> Yes, you're right. I did not think about it. So if we have a static
> pointer that may be resued, should not restore the pointer as at the
> beginning?
> static unsigned long *mc_groups = &mc_group_start;
> 
> At this moment we don't know how much memory is allocated. What do you
> think about this?

We do: mc_groups_longs.

> >                               new_groups = krealloc(mc_groups, nlen,
> >                                                     GFP_KERNEL);
> > -                             if (!new_groups)
> > +                             if (!new_groups) {
> > +                                     kfree(mc_groups);
> > +                                     mc_groups = &mc_group_start;
> >                                       return -ENOMEM;
> > +                             }

Seems wrong to shrink when we can't grow.  Whats the point?