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[209.132.180.67]) by mx.google.com with ESMTP id q3-v6si22421263pli.10.2018.11.12.15.22.34; Mon, 12 Nov 2018 15:22:50 -0800 (PST) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; dkim=pass header.i=@cisco.com header.s=iport header.b=Q0bRagzY; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=QUARANTINE sp=QUARANTINE dis=NONE) header.from=cisco.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727496AbeKMJRe (ORCPT + 99 others); Tue, 13 Nov 2018 04:17:34 -0500 Received: from rcdn-iport-8.cisco.com ([173.37.86.79]:44453 "EHLO rcdn-iport-8.cisco.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726078AbeKMJRe (ORCPT ); Tue, 13 Nov 2018 04:17:34 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=cisco.com; i=@cisco.com; l=6952; q=dns/txt; s=iport; t=1542064933; x=1543274533; h=subject:to:cc:references:from:message-id:date: mime-version:in-reply-to:content-transfer-encoding; bh=0m+QCKshc19lL3G72RcJnIOaoQHblaynbqMCK/tcmqU=; b=Q0bRagzY6ptj2qq6Ynsm79BT6/+eFXGBmBWQcGKO4+KH5hs1pVK+9TyG 754ux90PrRv9W/8zUfrVGabFdUYNSpeTzXKWQm/0EH8EMSg0PRDdddfgJ 3ZNoycTrcJ+n9YxhTLKMjvgwcLPpIA/rpAjpk311hUHuqG/dKE4jRcYmv U=; X-IronPort-AV: E=Sophos;i="5.54,497,1534809600"; d="scan'208";a="478585839" Received: from rcdn-core-1.cisco.com ([173.37.93.152]) by rcdn-iport-8.cisco.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 12 Nov 2018 23:22:13 +0000 Received: from [10.154.208.147] ([10.154.208.147]) by rcdn-core-1.cisco.com (8.15.2/8.15.2) with ESMTP id wACNM93F018652; Mon, 12 Nov 2018 23:22:10 GMT Subject: Re: [PATCH v5] kernel/signal: Signal-based pre-coredump notification To: Oleg Nesterov , Thomas Gleixner , Ingo Molnar , Borislav Petkov , "H. Peter Anvin" , Peter Zijlstra , Arnd Bergmann , "Eric W. Biederman" , Khalid Aziz , Kate Stewart , Helge Deller , Greg Kroah-Hartman , Al Viro , Andrew Morton , Christian Brauner , Catalin Marinas , Will Deacon , Dave Martin , Mauro Carvalho Chehab , Michal Hocko , Rik van Riel , "Kirill A. Shutemov" , Roman Gushchin , Marcos Paulo de Souza , Dominik Brodowski , Cyrill Gorcunov , Yang Shi , Jann Horn , Kees Cook Cc: x86@kernel.org, linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, "Victor Kamensky (kamensky)" , xe-linux-external@cisco.com, Stefan Strogin , Enke Chen References: <458c04d8-d189-4a26-729a-bb1d1d751534@cisco.com> <7741efa7-a3f8-62a1-ba52-613883164643@cisco.com> <84460a77-a111-404e-4bad-88104a6e246e@cisco.com> <20181026082812.GA10581@redhat.com> <21f678a8-4001-df36-c26e-e96cf203b1b1@cisco.com> <20181029111804.GA24820@redhat.com> <0c197608-3b7e-ffd1-8943-801a60beb917@cisco.com> From: Enke Chen Message-ID: Date: Mon, 12 Nov 2018 15:22:07 -0800 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.13; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <0c197608-3b7e-ffd1-8943-801a60beb917@cisco.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Auto-Response-Suppress: DR, OOF, AutoReply X-Outbound-SMTP-Client: 10.154.208.147, [10.154.208.147] X-Outbound-Node: rcdn-core-1.cisco.com Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, Folks: Could you please take care of this patch [PATCH 5]? Thanks. -- Enke On 10/29/18 3:31 PM, Enke Chen wrote: > For simplicity and consistency, this patch provides an implementation > for signal-based fault notification prior to the coredump of a child > process. A new prctl command, PR_SET_PREDUMP_SIG, is defined that can > be used by an application to express its interest and to specify the > signal for such a notification. > > Changes to prctl(2): > > PR_SET_PREDUMP_SIG (since Linux 4.20.x) > Set the child pre-coredump signal of the calling process to > arg2 (either a signal value in the range 1..maxsig, or 0 to > clear). This is the signal that the calling process will get > prior to the coredump of a child process. This value is > cleared across execve(2), or for the child of a fork(2). > > PR_GET_PREDUMP_SIG (since Linux 4.20.x) > Return the current value of the child pre-coredump signal, > in the location pointed to by (int *) arg2. > > Background: > > As the coredump of a process may take time, in certain time-sensitive > applications it is necessary for a parent process (e.g., a process > manager) to be notified of a child's imminent death before the coredump > so that the parent process can act sooner, such as re-spawning an > application process, or initiating a control-plane fail-over. > > One application is BFD. The early fault notification is a critical > component for maintaining BFD sessions (with a timeout value of > 50 msec or 100 msec) across a control-plane failure. > > Currently there are two ways for a parent process to be notified of a > child process's state change. One is to use the POSIX signal, and > another is to use the kernel connector module. The specific events and > actions are summarized as follows: > > Process Event POSIX Signal Connector-based > ---------------------------------------------------------------------- > ptrace_attach() do_notify_parent_cldstop() proc_ptrace_connector() > SIGCHLD / CLD_STOPPED > > ptrace_detach() do_notify_parent_cldstop() proc_ptrace_connector() > SIGCHLD / CLD_CONTINUED > > pre_coredump/ N/A proc_coredump_connector() > get_signal() > > post_coredump/ do_notify_parent() proc_exit_connector() > do_exit() SIGCHLD / exit_signal > ---------------------------------------------------------------------- > > As shown in the table, the signal-based pre-coredump notification is not > currently available. In some cases using a connector-based notification > can be quite complicated (e.g., when a process manager is written in shell > scripts and thus is subject to certain inherent limitations), and a > signal-based notification would be simpler and better suited. > > Signed-off-by: Enke Chen > Reviewed-by: Oleg Nesterov > --- > v4 -> v5: > Addressed review comments from Oleg Nesterov: > o use rcu_read_lock instead. > o revert back to notify the real_parent. > > fs/coredump.c | 23 +++++++++++++++++++++++ > fs/exec.c | 3 +++ > include/linux/sched/signal.h | 3 +++ > include/uapi/linux/prctl.h | 4 ++++ > kernel/sys.c | 13 +++++++++++++ > 5 files changed, 46 insertions(+) > > diff --git a/fs/coredump.c b/fs/coredump.c > index e42e17e..740b1bb 100644 > --- a/fs/coredump.c > +++ b/fs/coredump.c > @@ -536,6 +536,24 @@ static int umh_pipe_setup(struct subprocess_info *info, struct cred *new) > return err; > } > > +/* > + * While do_notify_parent() notifies the parent of a child's death post > + * its coredump, this function lets the parent (if so desired) know about > + * the imminent death of a child just prior to its coredump. > + */ > +static void do_notify_parent_predump(void) > +{ > + struct task_struct *parent; > + int sig; > + > + rcu_read_lock(); > + parent = rcu_dereference(current->real_parent); > + sig = parent->signal->predump_signal; > + if (sig != 0) > + do_send_sig_info(sig, SEND_SIG_NOINFO, parent, PIDTYPE_TGID); > + rcu_read_unlock(); > +} > + > void do_coredump(const kernel_siginfo_t *siginfo) > { > struct core_state core_state; > @@ -590,6 +608,11 @@ void do_coredump(const kernel_siginfo_t *siginfo) > if (retval < 0) > goto fail_creds; > > + /* > + * Send the pre-coredump signal to the parent if requested. > + */ > + do_notify_parent_predump(); > + > old_cred = override_creds(cred); > > ispipe = format_corename(&cn, &cprm); > diff --git a/fs/exec.c b/fs/exec.c > index fc281b7..7714da7 100644 > --- a/fs/exec.c > +++ b/fs/exec.c > @@ -1181,6 +1181,9 @@ static int de_thread(struct task_struct *tsk) > /* we have changed execution domain */ > tsk->exit_signal = SIGCHLD; > > + /* Clear the pre-coredump signal before loading a new binary */ > + sig->predump_signal = 0; > + > #ifdef CONFIG_POSIX_TIMERS > exit_itimers(sig); > flush_itimer_signals(); > diff --git a/include/linux/sched/signal.h b/include/linux/sched/signal.h > index 13789d1..728ef68 100644 > --- a/include/linux/sched/signal.h > +++ b/include/linux/sched/signal.h > @@ -112,6 +112,9 @@ struct signal_struct { > int group_stop_count; > unsigned int flags; /* see SIGNAL_* flags below */ > > + /* The signal sent prior to a child's coredump */ > + int predump_signal; > + > /* > * PR_SET_CHILD_SUBREAPER marks a process, like a service > * manager, to re-parent orphan (double-forking) child processes > diff --git a/include/uapi/linux/prctl.h b/include/uapi/linux/prctl.h > index c0d7ea0..79f0a8a 100644 > --- a/include/uapi/linux/prctl.h > +++ b/include/uapi/linux/prctl.h > @@ -219,4 +219,8 @@ struct prctl_mm_map { > # define PR_SPEC_DISABLE (1UL << 2) > # define PR_SPEC_FORCE_DISABLE (1UL << 3) > > +/* Whether to receive signal prior to child's coredump */ > +#define PR_SET_PREDUMP_SIG 54 > +#define PR_GET_PREDUMP_SIG 55 > + > #endif /* _LINUX_PRCTL_H */ > diff --git a/kernel/sys.c b/kernel/sys.c > index 123bd73..39aa3b8 100644 > --- a/kernel/sys.c > +++ b/kernel/sys.c > @@ -2476,6 +2476,19 @@ int __weak arch_prctl_spec_ctrl_set(struct task_struct *t, unsigned long which, > return -EINVAL; > error = arch_prctl_spec_ctrl_set(me, arg2, arg3); > break; > + case PR_SET_PREDUMP_SIG: > + if (arg3 || arg4 || arg5) > + return -EINVAL; > + if (!valid_signal((int)arg2)) > + return -EINVAL; > + me->signal->predump_signal = (int)arg2; > + break; > + case PR_GET_PREDUMP_SIG: > + if (arg3 || arg4 || arg5) > + return -EINVAL; > + error = put_user(me->signal->predump_signal, > + (int __user *)arg2); > + break; > default: > error = -EINVAL; > break; >