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From:   Curtis Malainey <cujomalainey@google.com>
Date:   Tue, 26 Mar 2019 10:35:41 -0700
Message-ID: <CAOReqxhLmTBZx04FZaeS_-9f6bk1RwJ_31UqB8MQ=KyB-5Ou=Q@mail.gmail.com>
Subject: Re: [PATCH] ASoC: core: Fix use-after-free after deferred card registration
To:     Guenter Roeck <linux@roeck-us.net>
Cc:     Mark Brown <broonie@kernel.org>,
        Liam Girdwood <lgirdwood@gmail.com>,
        Jaroslav Kysela <perex@perex.cz>,
        Takashi Iwai <tiwai@suse.com>, alsa-devel@alsa-project.org,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Curtis Malainey <cujomalainey@chromium.org>
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This has already been patched. See
https://mailman.alsa-project.org/pipermail/alsa-devel/2019-March/146150.html

On Tue, Mar 26, 2019 at 10:23 AM Guenter Roeck <linux@roeck-us.net> wrote:
>
> If snd_soc_register_card() fails because one of its links fails
> to instantiate with -EPROBE_DEFER, and the to-be-registered link
> is a legacy link, a subsequent retry will trigger a use-after-free
> and quite often a system crash.
>
> Example:
>
> byt-max98090 byt-max98090: ASoC: failed to init link Baytrail Audio
> byt-max98090 byt-max98090: snd_soc_register_card failed -517
> ....
> BUG: KASAN: use-after-free in snd_soc_init_platform+0x233/0x312
> Read of size 8 at addr ffff888067c43070 by task kworker/1:1/23
>
> snd_soc_init_platform() allocates memory attached to the card device.
> This memory is released when the card device is released. However,
> the pointer to the memory (dai_link->platforms) is only cleared from
> soc_cleanup_platform(), which is called from soc_cleanup_card_resources(),
> but not if snd_soc_register_card() fails early.
>
> Add the missing call to soc_cleanup_platform() in the error handling
> code of snd_soc_register_card() to fix the problem.
>
> Fixes: 78a24e10cd94 ("ASoC: soc-core: clear platform pointers on error")
> Cc: Curtis Malainey <cujomalainey@chromium.org>
> Signed-off-by: Guenter Roeck <linux@roeck-us.net>
> ---
>  sound/soc/soc-core.c | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/sound/soc/soc-core.c b/sound/soc/soc-core.c
> index 93d316d5bf8e..6bf9884d0863 100644
> --- a/sound/soc/soc-core.c
> +++ b/sound/soc/soc-core.c
> @@ -2799,6 +2799,7 @@ int snd_soc_register_card(struct snd_soc_card *card)
>                 if (ret) {
>                         dev_err(card->dev, "ASoC: failed to init link %s\n",
>                                 link->name);
> +                       soc_cleanup_platform(card);
>                         mutex_unlock(&client_mutex);
>                         return ret;
>                 }
> --
> 2.7.4
>