From mboxrd@z Thu Jan 1 00:00:00 1970 From: tip-bot for John Ogness Subject: [tip:core/urgent] fs/proc: Report eip/esp in /prod/PID/stat for coredumping Date: Fri, 15 Sep 2017 14:09:47 -0700 Message-ID: References: <87poatfwg6.fsf@linutronix.de> Reply-To: linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, peterz-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org, penguin-kernel-1yMVhJb1mP/7nzcFbJAaVXf5DAMn2ifp@public.gmane.org, brgerst-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org, akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org, tglx-hfZtesqFncYOwBW4kG4KsQ@public.gmane.org, linux-api-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, keescook-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org, john.ogness-hfZtesqFncYOwBW4kG4KsQ@public.gmane.org, luto-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org, tycho.andersen-Z7WLFzj8eWMS+FvcfC7Uqw@public.gmane.org, bp-Gina5bIWoIWzQB+pC5nmwQ@public.gmane.org, mingo-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org, hpa-YMNOUZJC4hwAvxtiuMwx3w@public.gmane.org, viro-RmSDqhL/yNMiFSDQTTA3OLVCufUGDwFn@public.gmane.org, torvalds-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org, marco.felsch-4vaI68m59Pc@public.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Return-path: In-Reply-To: <87poatfwg6.fsf-hfZtesqFncYOwBW4kG4KsQ@public.gmane.org> Content-Disposition: inline Sender: linux-api-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: linux-tip-commits-u79uwXL29TY76Z2rM5mHXA@public.gmane.org Cc: luto-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org, tycho.andersen-Z7WLFzj8eWMS+FvcfC7Uqw@public.gmane.org, bp-Gina5bIWoIWzQB+pC5nmwQ@public.gmane.org, mingo-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org, torvalds-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org, hpa-YMNOUZJC4hwAvxtiuMwx3w@public.gmane.org, viro-RmSDqhL/yNMiFSDQTTA3OLVCufUGDwFn@public.gmane.org, marco.felsch-4vaI68m59Pc@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, penguin-kernel-1yMVhJb1mP/7nzcFbJAaVXf5DAMn2ifp@public.gmane.org, peterz-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org, brgerst-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org, akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org, linux-api-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, tglx-hfZtesqFncYOwBW4kG4KsQ@public.gmane.org, keescook-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org, john.ogness-hfZtesqFncYOwBW4kG4KsQ@public.gmane.org List-Id: linux-api@vger.kernel.org Commit-ID: 451eb3f2053ea4eeb40f94947c542cfbd7636186 Gitweb: http://git.kernel.org/tip/451eb3f2053ea4eeb40f94947c542cfbd7636186 Author: John Ogness AuthorDate: Thu, 14 Sep 2017 11:42:17 +0200 Committer: Thomas Gleixner CommitDate: Fri, 15 Sep 2017 23:04:59 +0200 fs/proc: Report eip/esp in /prod/PID/stat for coredumping Commit 0a1eb2d474ed ("fs/proc: Stop reporting eip and esp in /proc/PID/stat") stopped reporting eip/esp because it is racey and dangerous for executing tasks. The comment adds: As far as I know, there are no use programs that make any material use of these fields, so just get rid of them. However, existing userspace core-dump-handler applications (for example, minicoredumper) are using these fields since they provide an excellent cross-platform interface to these valuable pointers. So that commit introduced a user space visible regression. Partially revert the change and make the readout possible for tasks with the proper permissions and only if the target task has the PF_DUMPCORE flag set. Fixes: 0a1eb2d474ed ("fs/proc: Stop reporting eip and esp in> /proc/PID/stat") Reported-by: Marco Felsch Signed-off-by: John Ogness Reviewed-by: Andy Lutomirski Cc: Tycho Andersen Cc: Kees Cook Cc: Peter Zijlstra Cc: Brian Gerst Cc: stable-u79uwXL29TY76Z2rM5mHXA@public.gmane.org Cc: Tetsuo Handa Cc: Borislav Petkov Cc: Al Viro Cc: Linux API Cc: Andrew Morton Cc: Linus Torvalds Link: http://lkml.kernel.org/r/87poatfwg6.fsf-hfZtesqFncYOwBW4kG4KsQ@public.gmane.org Signed-off-by: Thomas Gleixner --- fs/proc/array.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/fs/proc/array.c b/fs/proc/array.c index 88c3555..696cc68 100644 --- a/fs/proc/array.c +++ b/fs/proc/array.c @@ -421,7 +421,15 @@ static int do_task_stat(struct seq_file *m, struct pid_namespace *ns, * esp and eip are intentionally zeroed out. There is no * non-racy way to read them without freezing the task. * Programs that need reliable values can use ptrace(2). + * + * The only exception is if the task is core dumping because + * a program is not able to use ptrace(2) in that case. It is + * safe because the task has stopped executing permanently. */ + if (permitted && (task->flags & PF_DUMPCORE)) { + eip = KSTK_EIP(task); + esp = KSTK_ESP(task); + } } get_task_comm(tcomm, task);