linux-kernel - Re: BUG FIX: [PATCH RFC v3] memstick_check() memleak in kernel 6.1.0+ introduced pre 4.17

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Message-ID: <2023040127-untrue-obtrusive-1ea4@gregkh>
Date:   Sat, 1 Apr 2023 11:18:19 +0200
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Mirsad Goran Todorovac <mirsad.todorovac@....unizg.hr>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Thorsten Leemhuis <regressions@...mhuis.info>,
        Maxim Levitsky <maximlevitsky@...il.com>,
        Alex Dubov <oakad@...oo.com>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Jens Axboe <axboe@...nel.dk>,
        Christophe JAILLET <christophe.jaillet@...adoo.fr>,
        Hannes Reinecke <hare@...e.de>,
        Jiasheng Jiang <jiasheng@...as.ac.cn>,
        ye xingchen <ye.xingchen@....com.cn>, linux-mmc@...r.kernel.org
Subject: Re: BUG FIX: [PATCH RFC v3] memstick_check() memleak in kernel
 6.1.0+ introduced pre 4.17

On Sat, Apr 01, 2023 at 08:33:36AM +0200, Greg KH wrote:
> On Sat, Apr 01, 2023 at 08:28:07AM +0200, Greg KH wrote:
> > On Sat, Apr 01, 2023 at 08:23:26AM +0200, Mirsad Goran Todorovac wrote:
> > > > This patch is implying that anyone who calls "dev_set_name()" also has
> > > > to do this hack, which shouldn't be the case at all.
> > > > 
> > > > thanks,
> > > > 
> > > > greg k-h
> > > 
> > > This is my best guess. Unless there is dev_free_name() or kobject_free_name(), I don't
> > > see a more sensible way to patch this up.
> > 
> > In sleeping on this, I think this has to move to the driver core.  I
> > don't understand why we haven't seen this before, except maybe no one
> > has really noticed before (i.e. we haven't had good leak detection tools
> > that run with removable devices?)
> > 
> > Anyway, let me see if I can come up with something this weekend, give me
> > a chance...
> 
> Wait, no, this already should be handled by the kobject core, look at
> kobject_cleanup(), at the bottom.  So your change should be merely
> duplicating the logic there that already runs when the struct device is
> freed, right?
> 
> So I don't understand why your change works, odd.  I need more coffee...

I think you got half of the change correctly.  This init code is a maze
of twisty passages, let me take your patch and tweak it a bit into
something that I think should work.  This looks to be only a memstick
issue, not a driver core issue (which makes me feel better.)

thanks,

greg k-h