From: Oleg Nesterov <oleg@redhat.com>
To: Jiayuan Chen <jiayuan.chen@linux.dev>
Cc: linux-kernel@vger.kernel.org, mrpre@163.com, mkoutny@suse.com,
syzbot+adcaa842b762a1762e7d@syzkaller.appspotmail.com,
syzbot+fab52e3459fa2f95df57@syzkaller.appspotmail.com,
syzbot+0718f65353d72efaac1e@syzkaller.appspotmail.com,
Andrew Morton <akpm@linux-foundation.org>,
Christian Brauner <brauner@kernel.org>,
Lorenzo Stoakes <lorenzo.stoakes@oracle.com>,
"Liam R. Howlett" <Liam.Howlett@Oracle.com>,
Suren Baghdasaryan <surenb@google.com>,
Wei Yang <richard.weiyang@gmail.com>,
David Hildenbrand <david@redhat.com>,
Al Viro <viro@zeniv.linux.org.uk>,
Mateusz Guzik <mjguzik@gmail.com>,
Joel Granados <joel.granados@kernel.org>,
Bill O'Donnell <bodonnel@redhat.com>,
"Darrick J. Wong" <djwong@kernel.org>,
Frederic Weisbecker <frederic@kernel.org>
Subject: Re: [PATCH v2] pid: annotate data-races around pid_ns->pid_allocated
Date: Fri, 25 Apr 2025 12:07:07 +0200 [thread overview]
Message-ID: <20250425100707.GA8093@redhat.com> (raw)
In-Reply-To: <20250425055824.6930-1-jiayuan.chen@linux.dev>
On 04/25, Jiayuan Chen wrote:
>
> @@ -2584,7 +2584,7 @@ __latent_entropy struct task_struct *copy_process(
> rseq_fork(p, clone_flags);
>
> /* Don't start children in a dying pid namespace */
> - if (unlikely(!(ns_of_pid(pid)->pid_allocated & PIDNS_ADDING))) {
> + if (unlikely(!(data_race(ns_of_pid(pid)->pid_allocated & PIDNS_ADDING)))) {
Well. data_race() just hides the potential problem. READ_ONCE() makes more
sense imo, even if I think there are no real problems with the current code.
Either way,
> @@ -271,13 +271,13 @@ struct pid *alloc_pid(struct pid_namespace *ns, pid_t *set_tid,
> upid = pid->numbers + ns->level;
> idr_preload(GFP_KERNEL);
> spin_lock(&pidmap_lock);
> - if (!(ns->pid_allocated & PIDNS_ADDING))
> + if (!(data_race(ns->pid_allocated & PIDNS_ADDING)))
again, you do not need data_race() or READ_ONCE() if you read the
data protected by pidmap_lock. But you still need WRITE_ONCE() when
->pid_allocated is modified.
Oleg.
prev parent reply other threads:[~2025-04-25 10:08 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-04-25 5:58 [PATCH v2] pid: annotate data-races around pid_ns->pid_allocated Jiayuan Chen
2025-04-25 9:25 ` Michal Koutný
2025-04-28 8:30 ` Jiayuan Chen
2025-04-25 10:07 ` Oleg Nesterov [this message]
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