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Date: Thu, 12 Feb 2015 10:45:44 +0300
From: Cyrill Gorcunov <gorcunov@gmail.com>
To: Calvin Owens <calvinowens@fb.com>
Cc: "Kirill A. Shutemov" <kirill@shutemov.name>,
        Andrew Morton <akpm@linux-foundation.org>,
        Alexey Dobriyan <adobriyan@gmail.com>, Oleg Nesterov <oleg@redhat.com>,
        "Eric W. Biederman" <ebiederm@xmission.com>,
        Al Viro <viro@zeniv.linux.org.uk>,
        "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
        Peter Feiner <pfeiner@google.com>,
        Grant Likely <grant.likely@secretlab.ca>,
        Siddhesh Poyarekar <siddhesh.poyarekar@gmail.com>,
        linux-kernel@vger.kernel.org, kernel-team@fb.com,
        Pavel Emelyanov <xemul@openvz.org>
Subject: Re: [RFC][PATCH v3] procfs: Always expose /proc/<pid>/map_files/ and
 make it readable
Message-ID: <20150212074544.GV2253@moon>
References: <1421194829-28696-1-git-send-email-calvinowens@fb.com>
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On Wed, Feb 11, 2015 at 06:29:10PM -0800, Calvin Owens wrote:
> Currently, /proc/<pid>/map_files/ is restricted to CAP_SYS_ADMIN, and is
> only exposed if CONFIG_CHECKPOINT_RESTORE is set. This interface is
> useful for enumerating the files mapped into a process when the more
> verbose information in /proc/<pid>/maps is not needed. It also allows
> access to file descriptors for files that have been deleted and closed
> but are still mmapped into a process, which can be very useful for
> introspection and debugging.
...
>  
> +/*
> + * Enforce stronger PTRACE_MODE_ATTACH permissions on the symlinks under
> + * /proc/<pid>/map_files, since these links may refer to deleted or O_TMPFILE
> + * files that users might assume are inaccessible regardless of their
> + * ownership/permissions.
> + */
> +static void *proc_map_files_follow_link(struct dentry *dentry, struct nameidata *nd)
> +{
> +	struct inode *inode = dentry->d_inode;
> +	struct task_struct *task;
> +	int allowed = 0;
> +
> +	task = get_proc_task(inode);
> +	if (task) {
> +		allowed = ptrace_may_access(task, PTRACE_MODE_ATTACH);
> +		put_task_struct(task);
> +	}

	else
		return ERR_PTR(-ESRCH);

Other than that, looks good to me, thanks!

Rewieved-by: Cyrill Gorcunov <gorcunov@openvz.org>