linux-kernel - Re: [PATCH 5.16 077/227] iwlwifi: fix use-after-free

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Message-ID: <87h78swggw.fsf@kernel.org>
Date:   Mon, 21 Feb 2022 14:29:19 +0200
From:   Kalle Valo <kvalo@...nel.org>
To:     Thorsten Leemhuis <regressions@...mhuis.info>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        Stefan Agner <stefan@...er.ch>,
        Wolfgang Walter <linux@...m.de>,
        Jason Self <jason@...ehome.net>,
        Dominik Behr <dominik@...inikbehr.com>,
        Marek Marczykowski-Górecki 
        <marmarek@...isiblethingslab.com>,
        Johannes Berg <johannes.berg@...el.com>
Subject: Re: [PATCH 5.16 077/227] iwlwifi: fix use-after-free

Thorsten Leemhuis <regressions@...mhuis.info> writes:

> Hi, this is your Linux kernel regression tracker.
>
> On 21.02.22 09:48, Greg Kroah-Hartman wrote:
>> From: Johannes Berg <johannes.berg@...el.com>
>> 
>> commit bea2662e7818e15d7607d17d57912ac984275d94 upstream.
>> 
>> If no firmware was present at all (or, presumably, all of the
>> firmware files failed to parse), we end up unbinding by calling
>> device_release_driver(), which calls remove(), which then in
>> iwlwifi calls iwl_drv_stop(), freeing the 'drv' struct. However
>> the new code I added will still erroneously access it after it
>> was freed.
>> 
>> Set 'failure=false' in this case to avoid the access, all data
>> was already freed anyway.
>> 
>> Cc: stable@...r.kernel.org
>> Reported-by: Stefan Agner <stefan@...er.ch>
>> Reported-by: Wolfgang Walter <linux@...m.de>
>> Reported-by: Jason Self <jason@...ehome.net>
>> Reported-by: Dominik Behr <dominik@...inikbehr.com>
>> Reported-by: Marek Marczykowski-Górecki <marmarek@...isiblethingslab.com>
>> Fixes: ab07506b0454 ("iwlwifi: fix leaks/bad data after failed firmware load")
>> Signed-off-by: Johannes Berg <johannes.berg@...el.com>
>> Signed-off-by: Kalle Valo <kvalo@...nel.org>
>> Link:
>> https://lore.kernel.org/r/20220208114728.e6b514cf4c85.Iffb575ca2a623d7859b542c33b2a507d01554251@changeid
>> Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
>
> Great to see that you quickly picked up this patch. Once the new stable
> and longterm releases are out on Wednesday, it will fix a regression
> that made it into many stable and longterm kernels nearly four weeks
> earlier. I tracked the issue, which made me we wonder: should I have
> done something differently in this case to get the regression resolved
> more quickly? Should I maybe have suggested to remove the culprit
> temporarily until the fix was merged to mainline?
>
> For context, this is the story of the regression afaics: the change
> ab07506b0454 ("iwlwifi: fix leaks/bad data after failed firmware load")
> was merged for 5.17-rc1 (released on 2022-01-23). Shortly after it was
> backported to several stable/longterm series with new versions released
> on 2022-01-27. It triggered a general protection fault, if the proper
> firmware file was missing. Afaics at least five people reported the
> problem between 2022-02-01 and 2022-02-11 for at least 5.10.y, 5.15.y
> and 5.16.y (some of those reports were on the stable list), which shows
> that such a setup is not that unusual. A fix was posted on 2022-02-08
> and approved and committed by a maintainer on 2022-02-10. It was then
> merged to mainline on 2022-02-17 (I hope we can find ways to reduce such
> particular timeframes in the future, but that's a different story).

>From mainline point of view there is not really any easy way to make
this faster. There are multiple trees involved and pull requests always
take time (we cannot submit a pull request for every commit sepately),

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