diff mbox series

[4.19,56/71] fork: fix copy_process(CLONE_PARENT) race with the exiting ->real_parent

Message ID 20201109125022.535216218@linuxfoundation.org
State New
Headers show
Series None | expand

Commit Message

Greg Kroah-Hartman Nov. 9, 2020, 12:55 p.m. UTC 
From: Eddy Wu <itseddy0402@gmail.com>

commit b4e00444cab4c3f3fec876dc0cccc8cbb0d1a948 upstream.

current->group_leader->exit_signal may change during copy_process() if
current->real_parent exits.

Move the assignment inside tasklist_lock to avoid the race.

Signed-off-by: Eddy Wu <eddy_wu@trendmicro.com>
Acked-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 kernel/fork.c |   10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)
diff mbox series

Patch

--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1965,14 +1965,9 @@  static __latent_entropy struct task_stru
 	/* ok, now we should be set up.. */
 	p->pid = pid_nr(pid);
 	if (clone_flags & CLONE_THREAD) {
-		p->exit_signal = -1;
 		p->group_leader = current->group_leader;
 		p->tgid = current->tgid;
 	} else {
-		if (clone_flags & CLONE_PARENT)
-			p->exit_signal = current->group_leader->exit_signal;
-		else
-			p->exit_signal = (clone_flags & CSIGNAL);
 		p->group_leader = p;
 		p->tgid = p->pid;
 	}
@@ -2017,9 +2012,14 @@  static __latent_entropy struct task_stru
 	if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) {
 		p->real_parent = current->real_parent;
 		p->parent_exec_id = current->parent_exec_id;
+		if (clone_flags & CLONE_THREAD)
+			p->exit_signal = -1;
+		else
+			p->exit_signal = current->group_leader->exit_signal;
 	} else {
 		p->real_parent = current;
 		p->parent_exec_id = current->self_exec_id;
+		p->exit_signal = (clone_flags & CSIGNAL);
 	}
 
 	klp_copy_process(p);