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Date:   Tue, 29 Dec 2020 23:42:02 +0100
From:   Pavel Machek <pavel@ucw.cz>
To:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc:     linux-kernel@vger.kernel.org, stable@vger.kernel.org,
        Hulk Robot <hulkci@huawei.com>,
        Qinglang Miao <miaoqinglang@huawei.com>,
        Ulf Hansson <ulf.hansson@linaro.org>,
        Sasha Levin <sashal@kernel.org>
Subject: Re: [PATCH 5.10 191/717] memstick: fix a double-free bug in
 memstick_check
Message-ID: <20201229224202.GA32501@amd>
References: <20201228125020.963311703@linuxfoundation.org>
 <20201228125030.121361557@linuxfoundation.org>
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Hi!

> From: Qinglang Miao <miaoqinglang@huawei.com>
>=20
> [ Upstream commit e3e9ced5c93803d5b2ea1942c4bf0192622531d6 ]
>=20
> kfree(host->card) has been called in put_device so that
> another kfree would raise cause a double-free bug.

> +++ b/drivers/memstick/core/memstick.c
> @@ -468,7 +468,6 @@ static void memstick_check(struct work_struct *work)
>  			host->card =3D card;
>  			if (device_register(&card->dev)) {
>  				put_device(&card->dev);
> -				kfree(host->card);
>  				host->card =3D NULL;
>  			}

Does the host->card =3D NULL need to be removed, too (and following code
refactored)? put_device() needs that pointer to be able to free it and
it can do so asynchronously.

This will cause crashes; they should be easy to reproduce with
CONFIG_DEBUG_KOBJECT_RELEASE due to delay in kobject_release() AFAICT.

Best regards,								Pavel

--=20
http://www.livejournal.com/~pavelmachek

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