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Tue, 03 Mar 2026 23:09:40 -0800 (PST) Received: from lima-ubuntu.hz.ali.com ([47.246.98.208]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2adfb6b416bsm190980875ad.61.2026.03.03.23.09.35 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 03 Mar 2026 23:09:40 -0800 (PST) From: Qing Wang To: Alexei Starovoitov , Daniel Borkmann , John Fastabend , Andrii Nakryiko , Martin KaFai Lau , Eduard Zingerman , Song Liu , Yonghong Song , KP Singh , Stanislav Fomichev , Hao Luo , Jiri Olsa Cc: bpf@vger.kernel.org, linux-kernel@vger.kernel.org, Qing Wang , syzbot+b4c5ad098c821bf8d8bc@syzkaller.appspotmail.com Subject: [PATCH] bpf: Fix use-after-free in __bpf_trace_run() Date: Wed, 4 Mar 2026 15:09:27 +0800 Message-Id: <20260304070927.178464-1-wangqing7171@gmail.com> X-Mailer: git-send-email 2.34.1 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" A use-after-free issue reported from syzbot exists in __bpf_trace_run(O). BUG: KASAN: slab-use-after-free in __bpf_trace_run kernel/trace/bpf_trace.c= :2075 [inline] -> struct bpf_prog *prog =3D link->link.prog; The link(struct bpf_raw_tp_link) was freed when link->link.prog. The root cause is that: both bpf_raw_tp_link and tp_probes are RCU-managed, but there is no synchronization between their lifecycles. The link can be freed via call_rcu() before tp_probes is freed via call_srcu()/call_rcu_tasks_trace(), causing the link's lifetime to be shorter than tp_probes. This allows __bpf_trace_run() to access the freed link when a tracepoint fires. Fix by calling tracepoint_synchronize_unregister() to ensure tp_probes is freed before allowing the link to be freed. The issue was introduced by commit d4dfc5700e86 ("bpf: pass whole link instead of prog when triggering raw tracepoint"), which changed tracepoint callbacks to receive bpf_raw_tp_link pointers instead of bpf_prog pointers. Prior to this commit, this issue did not occur because the bpf_prog was directly used and protected by reference counting. Fixes: d4dfc5700e86 ("bpf: pass whole link instead of prog when triggering = raw tracepoint") Reported-by: syzbot+b4c5ad098c821bf8d8bc@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=3Db4c5ad098c821bf8d8bc Tested-by: syzbot+b4c5ad098c821bf8d8bc@syzkaller.appspotmail.com Signed-off-by: Qing Wang --- kernel/bpf/syscall.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c index 0378e83b4099..fc93dd544162 100644 --- a/kernel/bpf/syscall.c +++ b/kernel/bpf/syscall.c @@ -3783,6 +3783,12 @@ static void bpf_raw_tp_link_release(struct bpf_link = *link) =20 bpf_probe_unregister(raw_tp->btp, raw_tp); bpf_put_raw_tracepoint(raw_tp->btp); + + /* + * Ensure tp_probes is freed before the link. This prevents + * use-after-free in __bpf_trace_run() when a tracepoint fires. + */ + tracepoint_synchronize_unregister(); } =20 static void bpf_raw_tp_link_dealloc(struct bpf_link *link) --=20 2.34.1