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Wed, 07 Jan 2026 01:41:08 -0800 (PST) From: Qing Wang To: oleg@redhat.com Cc: thaumy.love@gmail.com, Liam.Howlett@oracle.com, akpm@linux-foundation.org, brauner@kernel.org, bsegall@google.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, wangqing7171@gmail.com Subject: Re: [PATCH] fork/pid: Fix use-after-free in __task_pid_nr_ns Date: Wed, 7 Jan 2026 17:40:58 +0800 Message-Id: <20260107094058.3753465-1-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 20:50, 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. > > Oleg. I agree with your idea. But we don't need to fix this issue anymore, because after reviewing the current mainline code, I found that it has already been resolved(c418d8b4d7a4 "perf/core: Fix missing read event generation on task exit") by moving sync_child_event() from perf_child_detach() into perf_event_exit_event(). Here https://patch.msgid.link/20251209041600.963586-1-thaumy.love@gmail.com As a result, perf_event_read_event() no longer occurs on the problematic path reported (i.e., the close()->perf_release() path). Qing.