netdev - Re: [PATCH] genetlink: Prevent memory leak when krealloc fail

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Message-ID: <20231118134244.GB30289@breakpoint.cc>
Date: Sat, 18 Nov 2023 14:42:44 +0100
From: Florian Westphal <fw@...len.de>
To: Kamil Duljas <kamil.duljas@...il.com>
Cc: Florian Westphal <fw@...len.de>, Jakub Kicinski <kuba@...nel.org>,
	"David S . Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>, Paolo Abeni <pabeni@...hat.com>,
	Jiri Pirko <jiri@...nulli.us>,
	Johannes Berg <johannes@...solutions.net>, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] genetlink: Prevent memory leak when krealloc fail

Kamil Duljas <kamil.duljas@...il.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?