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Tue, 06 Jan 2026 18:43:21 -0800 (PST) From: Qing Wang To: oleg@redhat.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, wangqing7171@gmail.com Subject: Re: [PATCH] fork/pid: Fix use-after-free in __task_pid_nr_ns Date: Wed, 7 Jan 2026 10:43:12 +0800 Message-Id: <20260107024312.2868774-1-wangqing7171@gmail.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit On Tue, 06 Jan 2026 at 19:19, Oleg Nesterov wrote: > 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(). I agree with this. Let's make an new patch. > > --- 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/ I viewed this link. Your patches is not merged on master.