lkml.org 
[lkml]   [2011]   [Dec]   [7]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
SubjectRe: [PATCH] sys_getppid: add missing rcu_dereference
From
On Tue, Dec 6, 2011 at 6:45 PM, Mandeep Singh Baines <msb@chromium.org> wrote:
> In order to safely dereference current->real_parent inside an
> rcu_read_lock, we need an rcu_dereference.
>
> Signed-off-by: Mandeep Singh Baines <msb@chromium.org>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Pavel Emelyanov <xemul@openvz.org>
> Cc: Oleg Nesterov <oleg@redhat.com>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Kees Cook <keescook@chromium.org>
> ---
>  kernel/timer.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
>
> diff --git a/kernel/timer.c b/kernel/timer.c
> index dbaa624..9c3c62b 100644
> --- a/kernel/timer.c
> +++ b/kernel/timer.c
> @@ -1368,7 +1368,7 @@ SYSCALL_DEFINE0(getppid)
>        int pid;
>
>        rcu_read_lock();
> -       pid = task_tgid_vnr(current->real_parent);
> +       pid = task_tgid_vnr(rcu_dereference(current->real_parent));
>        rcu_read_unlock();
>
>        return pid;

Should parent and real_parent also be marked in sched.h with __rcu so
sparse can find other missing rcu_dereference()s? And if not, why?
(tasklist lock?)

I think I see at least are few other users (security/apparmor/audit.c,
security/tomoyo/common.h, kernel/sched.c) that need rcu_dereference()
when accessing real_parent, there are probably more.

-Kees

--
Kees Cook
ChromeOS Security
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2011-12-08 00:05    [from the cache]
©2003-2011 Jasper Spaans