linux-kernel - [PATCH 4/9] signal: Factor start_group_exit out of complete

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Date:   Thu, 24 Jun 2021 14:01:20 -0500
From:   ebiederm@...ssion.com (Eric W. Biederman)
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Al Viro <viro@...iv.linux.org.uk>,
        Michael Schmitz <schmitzmic@...il.com>,
        linux-arch <linux-arch@...r.kernel.org>,
        Jens Axboe <axboe@...nel.dk>, Oleg Nesterov <oleg@...hat.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Richard Henderson <rth@...ddle.net>,
        Ivan Kokshaysky <ink@...assic.park.msu.ru>,
        Matt Turner <mattst88@...il.com>,
        alpha <linux-alpha@...r.kernel.org>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        linux-m68k <linux-m68k@...ts.linux-m68k.org>,
        Arnd Bergmann <arnd@...nel.org>,
        Ley Foon Tan <ley.foon.tan@...el.com>,
        Tejun Heo <tj@...nel.org>, Kees Cook <keescook@...omium.org>
Subject: [PATCH 4/9] signal: Factor start_group_exit out of complete_signal


Signed-off-by: "Eric W. Biederman" <ebiederm@...ssion.com>
---
 include/linux/sched/signal.h |  2 ++
 kernel/signal.c              | 52 +++++++++++++++++++++++++-----------
 2 files changed, 39 insertions(+), 15 deletions(-)

diff --git a/include/linux/sched/signal.h b/include/linux/sched/signal.h
index 774be5d3ac3e..c007e55cb119 100644
--- a/include/linux/sched/signal.h
+++ b/include/linux/sched/signal.h
@@ -428,6 +428,8 @@ static inline void ptrace_signal_wake_up(struct task_struct *t, bool resume)
 	signal_wake_up_state(t, resume ? __TASK_TRACED : 0);
 }
 
+void start_group_exit(int exit_code);
+
 void task_join_group_stop(struct task_struct *task);
 
 #ifdef TIF_RESTORE_SIGMASK
diff --git a/kernel/signal.c b/kernel/signal.c
index da37cc4515f2..c79c010ca5f3 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -1027,6 +1027,42 @@ static inline bool wants_signal(int sig, struct task_struct *p)
 	return task_curr(p) || !task_sigpending(p);
 }
 
+static void start_group_exit_locked(struct signal_struct *signal, int exit_code)
+{
+	/*
+	 * Start a group exit and wake everybody up.
+	 * This way we don't have other threads
+	 * running and doing things after a slower
+	 * thread has the fatal signal pending.
+	 */
+	struct task_struct *t;
+
+	signal->flags = SIGNAL_GROUP_EXIT;
+	signal->group_exit_code = exit_code;
+	signal->group_stop_count = 0;
+	__for_each_thread(signal, t) {
+		task_clear_jobctl_pending(t, JOBCTL_PENDING_MASK);
+
+		/* Don't bother with already dead threads */
+		if (t->exit_state)
+			continue;
+		sigaddset(&t->pending.signal, SIGKILL);
+		signal_wake_up(t, 1);
+	}
+}
+
+void start_group_exit(int exit_code)
+{
+	if (!fatal_signal_pending(current)) {
+		struct sighand_struct *const sighand = current->sighand;
+
+		spin_lock_irq(&sighand->siglock);
+		if (!fatal_signal_pending(current))
+			start_group_exit_locked(current->signal, exit_code);
+		spin_unlock_irq(&sighand->siglock);
+	}
+}
+
 static void complete_signal(int sig, struct task_struct *p, enum pid_type type)
 {
 	struct signal_struct *signal = p->signal;
@@ -1076,21 +1112,7 @@ static void complete_signal(int sig, struct task_struct *p, enum pid_type type)
 		 * This signal will be fatal to the whole group.
 		 */
 		if (!sig_kernel_coredump(sig)) {
-			/*
-			 * Start a group exit and wake everybody up.
-			 * This way we don't have other threads
-			 * running and doing things after a slower
-			 * thread has the fatal signal pending.
-			 */
-			signal->flags = SIGNAL_GROUP_EXIT;
-			signal->group_exit_code = sig;
-			signal->group_stop_count = 0;
-			t = p;
-			do {
-				task_clear_jobctl_pending(t, JOBCTL_PENDING_MASK);
-				sigaddset(&t->pending.signal, SIGKILL);
-				signal_wake_up(t, 1);
-			} while_each_thread(p, t);
+			start_group_exit_locked(signal, sig);
 			return;
 		}
 	}
-- 
2.20.1