linux-kernel - Re: [PATCH 5.10 086/103] regmap: debugfs: Fix a memory leak when calling regmap_attach

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Message-ID: <20210115202221.GA209258@ubuntu-m3-large-x86>
Date:   Fri, 15 Jan 2021 13:22:21 -0700
From:   Nathan Chancellor <natechancellor@...il.com>
To:     Pavel Machek <pavel@....cz>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        Xiaolei Wang <xiaolei.wang@...driver.com>,
        Mark Brown <broonie@...nel.org>
Subject: Re: [PATCH 5.10 086/103] regmap: debugfs: Fix a memory leak when
 calling regmap_attach_dev

On Fri, Jan 15, 2021 at 09:18:19PM +0100, Pavel Machek wrote:
> Hi!
> 
> > From: Xiaolei Wang <xiaolei.wang@...driver.com>
> > 
> > commit cffa4b2122f5f3e53cf3d529bbc74651f95856d5 upstream.
> > 
> > After initializing the regmap through
> > syscon_regmap_lookup_by_compatible, then regmap_attach_dev to the
> > device, because the debugfs_name has been allocated, there is no
> > need to redistribute it again
> 
> ? redistribute?
> 
> Anyway, this patch is clearly buggy:
> 
> >  
> >  	if (!strcmp(name, "dummy")) {
> > -		kfree(map->debugfs_name);
> > +		if (!map->debugfs_name)
> > +			kfree(map->debugfs_name);
> >  
> 
> It runs kfree only if the variable is NULL. That's clearly useless,
> kfree(NULL) is NOP, and this causes memory leak.

Fixed by commit f6bcb4c7f366 ("regmap: debugfs: Fix a reversed if
statement in regmap_debugfs_init()") in mainline.

Cheers,
Nathan