linux-kernel - Re: [syzbot] [mm?] general protection fault in find_lock_task

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Message-ID: <20241217103105.151-1-hdanton@sina.com>
Date: Tue, 17 Dec 2024 18:31:04 +0800
From: Hillf Danton <hdanton@...a.com>
To: syzbot <syzbot+c2e074db555379260750@...kaller.appspotmail.com>
Cc: linux-kernel@...r.kernel.org,
	syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [mm?] general protection fault in find_lock_task_mm

On Mon, 16 Dec 2024 11:16:28 -0800
> syzbot found the following issue on:
> 
> HEAD commit:    231825b2e1ff Revert "unicode: Don't special case ignorable..
> git tree:       upstream
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=102844f8580000

#syz test

--- x/mm/oom_kill.c
+++ y/mm/oom_kill.c
@@ -137,7 +137,10 @@ struct task_struct *find_lock_task_mm(st
 	rcu_read_lock();
 
 	for_each_thread(p, t) {
+		if (!tryget_task_struct(t))
+			continue;
 		task_lock(t);
+		put_task_struct(t);
 		if (likely(t->mm))
 			goto found;
 		task_unlock(t);
--