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Tue, 27 Jan 2026 00:37:26 -0800 (PST) From: Qing Wang To: henryzhangjcle@gmail.com Cc: acme@kernel.org, linux-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org, mingo@redhat.com, peterz@infradead.org, syzbot+2a077cb788749964cf68@syzkaller.appspotmail.com, syzkaller-bugs@googlegroups.com, zeri@umich.edu Subject: Re: [PATCH] perf: Fix data race in perf_event_set_bpf_handler() Date: Tue, 27 Jan 2026 16:37:19 +0800 Message-Id: <20260127083719.1347209-1-wangqing7171@gmail.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20260127023618.1469937-1-zeri@umich.edu> References: <20260127023618.1469937-1-zeri@umich.edu> 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, 27 Jan 2026 at 10:36, Henry Zhang wrote: > diff --git a/kernel/events/core.c b/kernel/events/core.c > index a0fa488bce84..1f3ed9e87507 100644 > --- a/kernel/events/core.c > +++ b/kernel/events/core.c > @@ -10349,7 +10349,7 @@ static inline int perf_event_set_bpf_handler(struct perf_event *event, > return -EPROTO; > } > > - event->prog = prog; > + WRITE_ONCE(event->prog, prog); > event->bpf_cookie = bpf_cookie; > return 0; > } > @@ -10407,7 +10407,9 @@ static int __perf_event_overflow(struct perf_event *event, > if (event->attr.aux_pause) > perf_event_aux_pause(event->aux_event, true); > > - if (event->prog && event->prog->type == BPF_PROG_TYPE_PERF_EVENT && > + struct bpf_prog *prog = READ_ONCE(event->prog); > + > + if (prog && prog->type == BPF_PROG_TYPE_PERF_EVENT && > !bpf_overflow_handler(event, data, regs)) > goto out; Looking at this code, I guess there may be an serious issue: a potential use-after-free (UAF) risk when accessing event->prog in __perf_event_overflow. CPU 0 (interrupt context) CPU 1 (process context) read event->prog perf_event_free_bpf_handler() put(prog) free(prog) access memory pointed to by prog This scenario need to be more analysis. -- Qing