From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 21227C18E5C for ; Tue, 10 Mar 2020 21:22:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 05C15222C4 for ; Tue, 10 Mar 2020 21:22:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727610AbgCJVWE (ORCPT ); Tue, 10 Mar 2020 17:22:04 -0400 Received: from youngberry.canonical.com ([91.189.89.112]:58083 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727504AbgCJVWC (ORCPT ); Tue, 10 Mar 2020 17:22:02 -0400 Received: from ip5f5bf7ec.dynamic.kabel-deutschland.de ([95.91.247.236] helo=wittgenstein) by youngberry.canonical.com with esmtpsa (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.86_2) (envelope-from ) id 1jBmJc-0000N4-9H; Tue, 10 Mar 2020 21:21:28 +0000 Date: Tue, 10 Mar 2020 22:21:24 +0100 From: Christian Brauner To: "Eric W. Biederman" Cc: Bernd Edlinger , Kees Cook , Jann Horn , Jonathan Corbet , Alexander Viro , Andrew Morton , Alexey Dobriyan , Thomas Gleixner , Oleg Nesterov , Frederic Weisbecker , Andrei Vagin , Ingo Molnar , "Peter Zijlstra (Intel)" , Yuyang Du , David Hildenbrand , Sebastian Andrzej Siewior , Anshuman Khandual , David Howells , James Morris , Greg Kroah-Hartman , Shakeel Butt , Jason Gunthorpe , Christian Kellner , Andrea Arcangeli , Aleksa Sarai , "Dmitry V. Levin" , "linux-doc@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "linux-fsdevel@vger.kernel.org" , "linux-mm@kvack.org" , "stable@vger.kernel.org" , "linux-api@vger.kernel.org" Subject: Re: [PATCH v2 2/5] exec: Factor unshare_sighand out of de_thread and call it separately Message-ID: <20200310212124.l6rajcjkitt65fxr@wittgenstein> References: <87v9nlii0b.fsf@x220.int.ebiederm.org> <87a74xi4kz.fsf@x220.int.ebiederm.org> <87r1y8dqqz.fsf@x220.int.ebiederm.org> <87tv32cxmf.fsf_-_@x220.int.ebiederm.org> <87v9ne5y4y.fsf_-_@x220.int.ebiederm.org> <87k13u5y26.fsf_-_@x220.int.ebiederm.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <87k13u5y26.fsf_-_@x220.int.ebiederm.org> Sender: linux-api-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-api@vger.kernel.org On Sun, Mar 08, 2020 at 04:36:17PM -0500, Eric W. Biederman wrote: > > This makes the code clearer and makes it easier to implement a mutex > that is not taken over any locations that may block indefinitely waiting > for userspace. > > Signed-off-by: "Eric W. Biederman" > --- > fs/exec.c | 39 ++++++++++++++++++++++++++------------- > 1 file changed, 26 insertions(+), 13 deletions(-) > > diff --git a/fs/exec.c b/fs/exec.c > index c3f34791f2f0..ff74b9a74d34 100644 > --- a/fs/exec.c > +++ b/fs/exec.c > @@ -1194,6 +1194,23 @@ static int de_thread(struct task_struct *tsk) > flush_itimer_signals(); > #endif > > + BUG_ON(!thread_group_leader(tsk)); > + return 0; > + > +killed: > + /* protects against exit_notify() and __exit_signal() */ > + read_lock(&tasklist_lock); > + sig->group_exit_task = NULL; > + sig->notify_count = 0; > + read_unlock(&tasklist_lock); > + return -EAGAIN; > +} > + > + > +static int unshare_sighand(struct task_struct *me) > +{ > + struct sighand_struct *oldsighand = me->sighand; > + > if (refcount_read(&oldsighand->count) != 1) { > struct sighand_struct *newsighand; > /* > @@ -1210,23 +1227,13 @@ static int de_thread(struct task_struct *tsk) > > write_lock_irq(&tasklist_lock); > spin_lock(&oldsighand->siglock); > - rcu_assign_pointer(tsk->sighand, newsighand); > + rcu_assign_pointer(me->sighand, newsighand); > spin_unlock(&oldsighand->siglock); > write_unlock_irq(&tasklist_lock); > > __cleanup_sighand(oldsighand); > } This is fine for now but we share an aweful lot of code with copy_sighand(). We should earmark this to look into consolidating the core operations into a common helper called from both copy_sighand() and unshare_sighand() maybe even dumbing it down to one helper. But not needed for now. Otherwise: Acked-by: Christian Brauner