From: Oleg Nesterov <oleg@redhat.com>
To: Qing Wang <wangqing7171@gmail.com>
Cc: Liam.Howlett@oracle.com, akpm@linux-foundation.org,
brauner@kernel.org, bsegall@google.com, david@kernel.org,
dietmar.eggemann@arm.com, jack@suse.cz, joel.granados@kernel.org,
juri.lelli@redhat.com, linux-kernel@vger.kernel.org,
lorenzo.stoakes@oracle.com, mingo@redhat.com, mjguzik@gmail.com,
peterz@infradead.org, rostedt@goodmis.org, rppt@kernel.org,
syzbot+e0378d4f4fe57aa2bdd0@syzkaller.appspotmail.com,
vbabka@suse.cz, vincent.guittot@linaro.org
Subject: Re: [PATCH] fork/pid: Fix use-after-free in __task_pid_nr_ns
Date: Tue, 6 Jan 2026 12:19:48 +0100 [thread overview]
Message-ID: <aVzv1HF-Ao6KkVRB@redhat.com> (raw)
In-Reply-To: <20260106105832.2779312-1-wangqing7171@gmail.com>
On 01/06, Qing Wang wrote:
>
> Could we put the checking 'pid_alive(task)' into __task_pid_nr_ns()?
I don't think so... see below.
> Because there is another similar use case here.
>
>
> arch/s390/kernel/perf_cpum_sf.c
> 619,9: pid = __task_pid_nr_ns(tsk, type, event->ns);
This case is not similar. This tsk was found by find_task_by_pid_ns(),
it must be fully initialized.
So I don't think it makes sense to add the additional check into
__task_pid_nr_ns().
> --- a/kernel/pid.c
> +++ b/kernel/pid.c
> @@ -515,7 +515,7 @@ pid_t __task_pid_nr_ns(struct task_struct *task, enum pid_type type,
> rcu_read_lock();
> if (!ns)
> ns = task_active_pid_ns(current);
> - if (ns)
> + if (ns && pid_alive(task))
This reminds me... the 2nd "if (ns) check must die. I'll ping Cristian.
See https://lore.kernel.org/all/20251015123613.GA9456@redhat.com/
Oleg.
next prev parent reply other threads:[~2026-01-06 11:20 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-01-05 4:36 [PATCH] fork/pid: Fix use-after-free in __task_pid_nr_ns Qing Wang
2026-01-05 22:46 ` Andrew Morton
2026-01-06 7:07 ` Qing Wang
2026-01-06 9:04 ` Oleg Nesterov
2026-01-06 10:06 ` Qing Wang
2026-01-06 10:26 ` Qing Wang
2026-01-06 10:58 ` Oleg Nesterov
2026-01-06 10:58 ` Qing Wang
2026-01-06 11:19 ` Oleg Nesterov [this message]
2026-01-07 2:43 ` Qing Wang
2026-01-06 12:50 ` Oleg Nesterov
2026-01-07 9:40 ` Qing Wang
2026-01-07 14:54 ` Oleg Nesterov
2026-01-07 9:43 ` Oleg Nesterov
[not found] <20260105045609.1764387-1-wangqing7171@gmail.com>
2026-01-07 20:39 ` Kees Cook
2026-01-08 2:15 ` Qing Wang
2026-01-08 3:44 ` Qing Wang
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