From: Enke Chen <enkechen@cisco.com>
To: Oleg Nesterov <oleg@redhat.com>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
"H. Peter Anvin" <hpa@zytor.com>,
Peter Zijlstra <peterz@infradead.org>,
Arnd Bergmann <arnd@arndb.de>,
"Eric W. Biederman" <ebiederm@xmission.com>,
Khalid Aziz <khalid.aziz@oracle.com>,
Kate Stewart <kstewart@linuxfoundation.org>,
Helge Deller <deller@gmx.de>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Al Viro <viro@zeniv.linux.org.uk>,
Andrew Morton <akpm@linux-foundation.org>,
Christian Brauner <christian@brauner.io>,
Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will.deacon@arm.com>,
Dave Martin <Dave.Martin@arm.com>,
Mauro Carvalho Chehab <mchehab+samsung@kernel.org>,
Michal Hocko <mhocko@kernel.org>, Rik van Riel <riel@surriel.com>,
"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
Roman Gushchin <guro@fb.com>,
Marcos Paulo de Souza <marcos.souza.org@gmail.com>,
Dominik Brodowski <linux@dominikbrodowski.net>,
Cyrill Gorcunov <gorcunov@openvz.org>,
Yang Shi <yang.shi@linux.alibaba.com>,
Jann Horn <jannh@google.com>, Kees Cook <keescook@chromium.org>
Cc: x86@kernel.org, linux-kernel@vger.kernel.org,
linux-arch@vger.kernel.org,
"Victor Kamensky (kamensky)" <kamensky@cisco.com>,
xe-linux-external@cisco.com, Stefan Strogin <sstrogin@cisco.com>,
Enke Chen <enkechen@cisco.com>
Subject: [PATCH v5] kernel/signal: Signal-based pre-coredump notification
Date: Mon, 29 Oct 2018 15:31:49 -0700 [thread overview]
Message-ID: <0c197608-3b7e-ffd1-8943-801a60beb917@cisco.com> (raw)
In-Reply-To: <20181029111804.GA24820@redhat.com>
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 <enkechen@cisco.com>
Reviewed-by: Oleg Nesterov <oleg@redhat.com>
---
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;
--
1.8.3.1
next prev parent reply other threads:[~2018-10-29 22:31 UTC|newest]
Thread overview: 70+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-10-13 0:33 [PATCH] kernel/signal: Signal-based pre-coredump notification Enke Chen
2018-10-13 6:40 ` Greg Kroah-Hartman
2018-10-15 18:16 ` Enke Chen
2018-10-15 18:43 ` Greg Kroah-Hartman
2018-10-15 18:49 ` Enke Chen
2018-10-15 18:58 ` Greg Kroah-Hartman
2018-10-13 10:44 ` Christian Brauner
2018-10-15 18:39 ` Enke Chen
2018-10-13 18:27 ` Jann Horn
2018-10-15 18:36 ` Enke Chen
2018-10-15 18:54 ` Jann Horn
2018-10-15 19:23 ` Enke Chen
2018-10-19 23:01 ` Enke Chen
2018-10-22 15:40 ` Jann Horn
2018-10-22 20:48 ` Enke Chen
2018-10-15 12:05 ` Oleg Nesterov
2018-10-15 18:54 ` Enke Chen
2018-10-15 19:17 ` Enke Chen
2018-10-15 19:26 ` Enke Chen
2018-10-16 14:14 ` Oleg Nesterov
2018-10-16 15:09 ` Eric W. Biederman
2018-10-17 0:39 ` Enke Chen
2018-10-15 21:21 ` Alan Cox
2018-10-15 21:31 ` Enke Chen
2018-10-15 23:28 ` Eric W. Biederman
2018-10-16 0:33 ` valdis.kletnieks
2018-10-16 0:54 ` Enke Chen
2018-10-16 15:26 ` Eric W. Biederman
2018-10-22 21:09 ` [PATCH v2] " Enke Chen
2018-10-23 9:23 ` Oleg Nesterov
2018-10-23 19:43 ` Enke Chen
2018-10-23 21:40 ` Enke Chen
2018-10-24 13:52 ` Oleg Nesterov
2018-10-24 21:56 ` Enke Chen
2018-10-24 5:39 ` [PATCH v3] " Enke Chen
2018-10-24 14:02 ` Oleg Nesterov
2018-10-24 22:02 ` Enke Chen
2018-10-25 22:56 ` [PATCH v4] " Enke Chen
2018-10-26 8:28 ` Oleg Nesterov
2018-10-26 22:23 ` Enke Chen
2018-10-29 11:18 ` Oleg Nesterov
2018-10-29 21:08 ` Enke Chen
2018-10-29 22:31 ` Enke Chen [this message]
2018-10-30 16:46 ` [PATCH v5] " Oleg Nesterov
2018-10-31 0:25 ` Enke Chen
2018-11-22 0:37 ` Andrew Morton
2018-11-22 1:09 ` Enke Chen
2018-11-22 1:18 ` Enke Chen
2018-11-22 1:33 ` Andrew Morton
2018-11-22 4:57 ` Enke Chen
2018-11-12 23:22 ` Enke Chen
2018-11-27 22:54 ` [PATCH v5 1/2] " Enke Chen
2018-11-28 15:19 ` Dave Martin
2018-11-29 0:15 ` Enke Chen
2018-11-29 11:55 ` Dave Martin
2018-11-30 0:27 ` Enke Chen
2018-11-30 12:03 ` Oleg Nesterov
2018-12-05 6:47 ` Jann Horn
2018-12-04 22:37 ` Andrew Morton
2018-12-06 17:29 ` Oleg Nesterov
2018-10-25 22:56 ` [PATCH] selftests/prctl: selftest for pre-coredump signal notification Enke Chen
2018-11-27 22:54 ` [PATCH v5 2/2] " Enke Chen
2018-10-24 13:29 ` [PATCH v2] kernel/signal: Signal-based pre-coredump notification Eric W. Biederman
2018-10-24 23:50 ` Enke Chen
2018-10-25 12:23 ` Eric W. Biederman
2018-10-25 20:45 ` Enke Chen
2018-10-25 21:24 ` Enke Chen
2018-10-25 21:56 ` Enke Chen
2018-10-25 13:45 ` Jann Horn
2018-10-25 20:21 ` Eric W. Biederman
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=0c197608-3b7e-ffd1-8943-801a60beb917@cisco.com \
--to=enkechen@cisco.com \
--cc=Dave.Martin@arm.com \
--cc=akpm@linux-foundation.org \
--cc=arnd@arndb.de \
--cc=bp@alien8.de \
--cc=catalin.marinas@arm.com \
--cc=christian@brauner.io \
--cc=deller@gmx.de \
--cc=ebiederm@xmission.com \
--cc=gorcunov@openvz.org \
--cc=gregkh@linuxfoundation.org \
--cc=guro@fb.com \
--cc=hpa@zytor.com \
--cc=jannh@google.com \
--cc=kamensky@cisco.com \
--cc=keescook@chromium.org \
--cc=khalid.aziz@oracle.com \
--cc=kirill.shutemov@linux.intel.com \
--cc=kstewart@linuxfoundation.org \
--cc=linux-arch@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux@dominikbrodowski.net \
--cc=marcos.souza.org@gmail.com \
--cc=mchehab+samsung@kernel.org \
--cc=mhocko@kernel.org \
--cc=mingo@redhat.com \
--cc=oleg@redhat.com \
--cc=peterz@infradead.org \
--cc=riel@surriel.com \
--cc=sstrogin@cisco.com \
--cc=tglx@linutronix.de \
--cc=viro@zeniv.linux.org.uk \
--cc=will.deacon@arm.com \
--cc=x86@kernel.org \
--cc=xe-linux-external@cisco.com \
--cc=yang.shi@linux.alibaba.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).