linux-kernel - Re: [PATCH] fsi:fsi-sbefifo: Fix possible concurrency use-after-free bugs in sbefifo_user

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Date:   Wed, 02 Jan 2019 09:34:53 +0000
From:   David Howells <dhowells@...hat.com>
To:     Jia-Ju Bai <baijiaju1990@...il.com>
Cc:     dhowells@...hat.com, benh@...nel.crashing.org, joel@....id.au,
        eajames@...ux.vnet.ibm.com, andrew@...id.au,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] fsi:fsi-sbefifo: Fix possible concurrency use-after-free bugs in sbefifo_user_release

Jia-Ju Bai <baijiaju1990@...il.com> wrote:

> +	mutex_lock(&user->file_lock);
>  	sbefifo_release_command(user);
>  	free_page((unsigned long)user->cmd_page);
> +	mutex_unlock(&user->file_lock);

It shouldn't be necessary to do the free_page() call inside the locked
section.

David