linux-kernel - Re: [RFC][PATCH v3] procfs: Always expose /proc/<pid>/map

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Message-ID: <20150212074544.GV2253@moon>
Date:	Thu, 12 Feb 2015 10:45:44 +0300
From:	Cyrill Gorcunov <gorcunov@...il.com>
To:	Calvin Owens <calvinowens@...com>
Cc:	"Kirill A. Shutemov" <kirill@...temov.name>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Alexey Dobriyan <adobriyan@...il.com>,
	Oleg Nesterov <oleg@...hat.com>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Al Viro <viro@...iv.linux.org.uk>,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	Peter Feiner <pfeiner@...gle.com>,
	Grant Likely <grant.likely@...retlab.ca>,
	Siddhesh Poyarekar <siddhesh.poyarekar@...il.com>,
	linux-kernel@...r.kernel.org, kernel-team@...com,
	Pavel Emelyanov <xemul@...nvz.org>
Subject: Re: [RFC][PATCH v3] procfs: Always expose /proc/<pid>/map_files/ and
 make it readable

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@...nvz.org>
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