linux-kernel - [PATCH 14/17] signal: Remove zap_other

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Date:   Mon,  3 Jan 2022 15:33:09 -0600
From:   "Eric W. Biederman" <ebiederm@...ssion.com>
To:     linux-kernel@...r.kernel.org
Cc:     linux-arch@...r.kernel.org,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Oleg Nesterov <oleg@...hat.com>,
        Al Viro <viro@...IV.linux.org.uk>,
        Kees Cook <keescook@...omium.org>, linux-api@...r.kernel.org,
        "Eric W. Biederman" <ebiederm@...ssion.com>
Subject: [PATCH 14/17] signal: Remove zap_other_threads

The two callers of zap_other_threads want different things. The
function do_group_exit wants to set the exit code and it does not care
about the number of threads exiting.  In de_thread the current thread
is not exiting so there is not really an exit code.

Since schedule_task_exit_locked factors out the tricky bits stop
sharing the loop in zap_other_threads between de_thread and
do_group_exit.

Signed-off-by: "Eric W. Biederman" <ebiederm@...ssion.com>
---
 fs/exec.c                    | 12 +++++++++---
 include/linux/sched/signal.h |  1 -
 kernel/exit.c                |  9 ++++++++-
 kernel/signal.c              | 17 -----------------
 4 files changed, 17 insertions(+), 22 deletions(-)

diff --git a/fs/exec.c b/fs/exec.c
index 82db656ca709..b9f646fddc51 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -1037,6 +1037,7 @@ static int de_thread(struct task_struct *tsk)
 	struct signal_struct *sig = tsk->signal;
 	struct sighand_struct *oldsighand = tsk->sighand;
 	spinlock_t *lock = &oldsighand->siglock;
+	struct task_struct *t;
 
 	if (thread_group_empty(tsk))
 		goto no_thread_group;
@@ -1055,9 +1056,14 @@ static int de_thread(struct task_struct *tsk)
 	}
 
 	sig->group_exec_task = tsk;
-	sig->notify_count = zap_other_threads(tsk);
-	if (!thread_group_leader(tsk))
-		sig->notify_count--;
+	sig->group_stop_count = 0;
+	sig->notify_count = 0;
+	__for_each_thread(sig, t) {
+		if (t == tsk)
+			continue;
+		sig->notify_count++;
+		schedule_task_exit_locked(t);
+	}
 
 	while (sig->notify_count) {
 		__set_current_state(TASK_KILLABLE);
diff --git a/include/linux/sched/signal.h b/include/linux/sched/signal.h
index 7c62b7c29cc0..eed54f9ea2fc 100644
--- a/include/linux/sched/signal.h
+++ b/include/linux/sched/signal.h
@@ -343,7 +343,6 @@ extern void force_sig(int);
 extern void force_fatal_sig(int);
 extern void force_exit_sig(int);
 extern int send_sig(int, struct task_struct *, int);
-extern int zap_other_threads(struct task_struct *p);
 extern struct sigqueue *sigqueue_alloc(void);
 extern void sigqueue_free(struct sigqueue *);
 extern int send_sigqueue(struct sigqueue *, struct pid *, enum pid_type);
diff --git a/kernel/exit.c b/kernel/exit.c
index aedefe5eb0eb..27bc0ccfea78 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -918,9 +918,16 @@ do_group_exit(int exit_code)
 		else if (sig->group_exec_task)
 			exit_code = 0;
 		else {
+			struct task_struct *t;
+
 			sig->group_exit_code = exit_code;
 			sig->flags = SIGNAL_GROUP_EXIT;
-			zap_other_threads(current);
+			sig->group_stop_count = 0;
+			__for_each_thread(sig, t) {
+				if (t == current)
+					continue;
+				schedule_task_exit_locked(t);
+			}
 		}
 		spin_unlock_irq(&sighand->siglock);
 	}
diff --git a/kernel/signal.c b/kernel/signal.c
index cbfb9020368e..b0201e05be40 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -1371,23 +1371,6 @@ void schedule_task_exit_locked(struct task_struct *task)
 	}
 }
 
-/*
- * Nuke all other threads in the group.
- */
-int zap_other_threads(struct task_struct *p)
-{
-	struct task_struct *t = p;
-	int count = 0;
-
-	p->signal->group_stop_count = 0;
-
-	while_each_thread(p, t) {
-		count++;
-		schedule_task_exit_locked(t);
-	}
-	return count;
-}
-
 struct sighand_struct *__lock_task_sighand(struct task_struct *tsk,
 					   unsigned long *flags)
 {
-- 
2.29.2