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From:   SeongJae Park <sj@kernel.org>
To:     Greg KH <gregkh@linuxfoundation.org>
Cc:     Jianglei Nie <niejianglei2021@163.com>, sj@kernel.org,
        akpm@linux-foundation.org, damon@lists.linux.dev,
        linux-mm@kvack.org, linux-kernel@vger.kernel.org,
        stable@vger.kernel.org
Subject: Re: [PATCH] mm/damon/reclaim: fix potential memory leak in damon_reclaim_init()
Date:   Sun, 24 Jul 2022 10:15:57 +0000
Message-Id: <20220724101557.3137-1-sj@kernel.org>
In-Reply-To: <YtzyXCR/OCLYRSPx@kroah.com>
References: 
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Hi Jianglei and Greg,

On Sun, 24 Jul 2022 09:18:52 +0200 Greg KH <gregkh@linuxfoundation.org> wrote:

> On Sun, Jul 24, 2022 at 02:52:24PM +0800, Jianglei Nie wrote:
> > damon_reclaim_init() allocates a memory chunk for ctx with
> > damon_new_ctx(). When damon_select_ops() fails, ctx is not released, which
> > will lead to a memory leak.
> > 
> > We should release the ctx with damon_destroy_ctx() when damon_select_ops()
> > fails to fix the memory leak.
> > 
> > Fixes: 4d69c3457821 ("mm/damon/reclaim: use damon_select_ops() instead of damon_{v,p}a_set_operations()")
> > Signed-off-by: Jianglei Nie <niejianglei2021@163.com>
> > ---
> >  mm/damon/reclaim.c | 4 +++-
> >  1 file changed, 3 insertions(+), 1 deletion(-)
> > 
> > diff --git a/mm/damon/reclaim.c b/mm/damon/reclaim.c
> > index 4b07c29effe9..0b3c7396cb90 100644
> > --- a/mm/damon/reclaim.c
> > +++ b/mm/damon/reclaim.c
> > @@ -441,8 +441,10 @@ static int __init damon_reclaim_init(void)
> >  	if (!ctx)
> >  		return -ENOMEM;
> >  
> > -	if (damon_select_ops(ctx, DAMON_OPS_PADDR))
> > +	if (damon_select_ops(ctx, DAMON_OPS_PADDR)) {
> > +		damon_destroy_ctx(ctx);
> >  		return -EINVAL;
> > +	}
> >  
> >  	ctx->callback.after_wmarks_check = damon_reclaim_after_wmarks_check;
> >  	ctx->callback.after_aggregation = damon_reclaim_after_aggregation;
> > -- 
> > 2.25.1
> > 
> 
> <formletter>
> 
> This is not the correct way to submit patches for inclusion in the
> stable kernel tree.  Please read:
>     https://www.kernel.org/doc/html/latest/process/stable-kernel-rules.html
> for how to do this properly.
> 
> </formletter>

Thank you for the notice, Greg.  Jianglei, please read that great document.

And Andrew already added the 'Fixes:' and 'Cc: stable@' tags in the patch when
he added[1] it in the mm tree.  Hence I think this would be merged in the
appropriate stable series once it gets merged in the mainline.

[1] https://lore.kernel.org/mm-commits/20220717004946.7AD93C34114@smtp.kernel.org/


Thanks,
SJ