linux-kernel - Re: [PATCH 6/9] procfs: add pid_seq_private struct to handle /proc/<pid>/{stat|stack}

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Date:	Mon, 26 May 2014 10:02:15 -0700
From:	Andy Lutomirski <luto@...capital.net>
To:	Djalal Harouni <tixxdz@...ndz.org>
Cc:	Kees Cook <keescook@...omium.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Alexey Dobriyan <adobriyan@...il.com>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Al Viro <viro@...iv.linux.org.uk>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Ingo Molnar <mingo@...nel.org>,
	Oleg Nesterov <oleg@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Linux FS Devel <linux-fsdevel@...r.kernel.org>
Subject: Re: [PATCH 6/9] procfs: add pid_seq_private struct to handle /proc/<pid>/{stat|stack}

On Mon, May 26, 2014 at 6:27 AM, Djalal Harouni <tixxdz@...ndz.org> wrote:
> This patch is preparation to handle sensitive ONE entries:
> /proc/<pid>/stat
> /proc/<pid>/stack
>
> These files use sequence iterators and we want to keep that logic, and
> their internal handler semantics.
>
> The sequence iterators stock the inode in the seq_file->private field,
> so in order to keep the semantic and to make the cached permission
> checks available during ->read(), we add the 'pid_seq_private' struct
> that contains both the inode and the cached permission. It will be the
> one referenced in the seq_file->private.
>
> This way the internal handlers of /proc/<pid>/{stat|stack} wont change.
>
> Signed-off-by: Djalal Harouni <tixxdz@...ndz.org>
> ---
>  fs/proc/internal.h | 11 +++++++++++
>  1 file changed, 11 insertions(+)
>
> diff --git a/fs/proc/internal.h b/fs/proc/internal.h
> index f5c452c..f28e4f01 100644
> --- a/fs/proc/internal.h
> +++ b/fs/proc/internal.h
> @@ -78,6 +78,17 @@ struct proc_inode {
>         struct inode vfs_inode;
>  };
>
> +/*
> + * Struct used by some /proc/<pid>/$entries that use sequence
> + * iterators.
> + * This struct will be saved in seq_file->private so seq handlers
> + * can access the inode and the cached permission checks of ->open().
> + */
> +struct pid_seq_private {
> +       int permitted;
> +       struct inode *inode;
> +};
> +
>  typedef int (*proc_read_fn_t)(char *page,
>                               struct task_struct *task, int permitted);

int opener_may_ptrace, please.
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