From: Oleg Nesterov <oleg@redhat.com>
To: Qing Wang <wangqing7171@gmail.com>
Cc: mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com,
vincent.guittot@linaro.org, akpm@linux-foundation.org,
david@kernel.org, dietmar.eggemann@arm.com, rostedt@goodmis.org,
bsegall@google.com, lorenzo.stoakes@oracle.com,
Liam.Howlett@oracle.com, vbabka@suse.cz, rppt@kernel.org,
brauner@kernel.org, mjguzik@gmail.com, jack@suse.cz,
joel.granados@kernel.org, linux-kernel@vger.kernel.org,
syzbot+e0378d4f4fe57aa2bdd0@syzkaller.appspotmail.com
Subject: Re: [PATCH] fork/pid: Fix use-after-free in __task_pid_nr_ns
Date: Wed, 7 Jan 2026 10:43:16 +0100 [thread overview]
Message-ID: <aV4qtP-8Iqg98wrw@redhat.com> (raw)
In-Reply-To: <aV0FL-GKYaCQmiBs@redhat.com>
On 01/06, Oleg Nesterov wrote:
>
> On a second thought...
>
> sched_fork() is called before perf_event_init_task(). So perhaps
> sync_child_event() could also check task->__state != TASK_NEW before
> perf_event_read_event() ?
>
> Not sure, I know nothing about perf. Would be nice if perf experts can
> take a look.
Or something else, but we can't rely on pid_alive() or ->signal != NULL
checks.
perf_event_init_task() is called soon after dup_task_struct(), so
pid_alive() is true and child->signal == current->signal.
Lets forget about use-after-free. What if perf_child_detach() paths
call __task_pid_nr_ns() before copy_signal/etc ? In this case
perf_event_pid/perf_event_tid will return the pids of the forking
process, not the child's pids.
Oleg.
next prev parent reply other threads:[~2026-01-07 9:43 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
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 [this message]
[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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