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[146.241.97.87]) by smtp.gmail.com with ESMTPSA id do39-20020a05620a2b2700b006fcc3858044sm11916151qkb.86.2022.12.15.04.50.45 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 15 Dec 2022 04:50:47 -0800 (PST) Message-ID: Subject: Re: [PATCH net v2] net: sched: ematch: reject invalid data From: Paolo Abeni To: Jun Nie , jhs@mojatatu.com, xiyou.wangcong@gmail.com, jiri@resnulli.us, davem@davemloft.net, edumazet@google.com, kuba@kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org Date: Thu, 15 Dec 2022 13:50:43 +0100 In-Reply-To: <20221214022058.3625300-1-jun.nie@linaro.org> References: <20221214022058.3625300-1-jun.nie@linaro.org> Content-Type: text/plain; charset="UTF-8" User-Agent: Evolution 3.42.4 (3.42.4-2.fc35) MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Wed, 2022-12-14 at 10:20 +0800, Jun Nie wrote: > syzbot reported below bug. Refuse to compare for invalid data case to fix > it. > > general protection fault, probably for non-canonical address 0xdffffc0000000001: 0000 [#1] PREEMPT SMP KASAN > KASAN: null-ptr-deref in range [0x0000000000000008-0x000000000000000f] > CPU: 0 PID: 6 Comm: kworker/0:0 Not tainted 5.15.77-syzkaller-00764-g7048384c9872 #0 > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/26/2022 > Workqueue: wg-crypt-wg2 wg_packet_tx_worker > RIP: 0010:em_cmp_match+0x4e/0x5f0 net/sched/em_cmp.c:25 > Call Trace: > > tcf_em_match net/sched/ematch.c:492 [inline] > __tcf_em_tree_match+0x194/0x720 net/sched/ematch.c:518 > tcf_em_tree_match include/net/pkt_cls.h:463 [inline] > basic_classify+0xd8/0x250 net/sched/cls_basic.c:48 > __tcf_classify net/sched/cls_api.c:1549 [inline] > tcf_classify+0x161/0x430 net/sched/cls_api.c:1589 > prio_classify net/sched/sch_prio.c:42 [inline] > prio_enqueue+0x1d3/0x6a0 net/sched/sch_prio.c:75 > dev_qdisc_enqueue net/core/dev.c:3792 [inline] > __dev_xmit_skb+0x35c/0x1650 net/core/dev.c:3876 > __dev_queue_xmit+0x8f3/0x1b50 net/core/dev.c:4193 > dev_queue_xmit+0x17/0x20 net/core/dev.c:4261 > neigh_hh_output include/net/neighbour.h:508 [inline] > neigh_output include/net/neighbour.h:522 [inline] > ip_finish_output2+0xc0f/0xf00 net/ipv4/ip_output.c:228 > __ip_finish_output+0x163/0x370 > ip_finish_output+0x20b/0x220 net/ipv4/ip_output.c:316 > NF_HOOK_COND include/linux/netfilter.h:299 [inline] > ip_output+0x1e9/0x410 net/ipv4/ip_output.c:430 > dst_output include/net/dst.h:450 [inline] > ip_local_out+0x92/0xb0 net/ipv4/ip_output.c:126 > iptunnel_xmit+0x4a2/0x890 net/ipv4/ip_tunnel_core.c:82 > udp_tunnel_xmit_skb+0x1b6/0x2c0 net/ipv4/udp_tunnel_core.c:175 > send4+0x78d/0xd20 drivers/net/wireguard/socket.c:85 > wg_socket_send_skb_to_peer+0xd5/0x1d0 drivers/net/wireguard/socket.c:175 > wg_packet_create_data_done drivers/net/wireguard/send.c:251 [inline] > wg_packet_tx_worker+0x202/0x560 drivers/net/wireguard/send.c:276 > process_one_work+0x6db/0xc00 kernel/workqueue.c:2313 > worker_thread+0xb3e/0x1340 kernel/workqueue.c:2460 > kthread+0x41c/0x500 kernel/kthread.c:319 > ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:298 > > Reported-by: syzbot+963f7637dae8becc038f@syzkaller.appspotmail.com > Fixes: e7096c131e51 ("net: WireGuard secure network tunnel") Very likely this is not the correct fixes tag. > Signed-off-by: Jun Nie > --- > net/sched/em_cmp.c | 7 ++++++- > 1 file changed, 6 insertions(+), 1 deletion(-) > > diff --git a/net/sched/em_cmp.c b/net/sched/em_cmp.c > index f17b049ea530..0284394be53f 100644 > --- a/net/sched/em_cmp.c > +++ b/net/sched/em_cmp.c > @@ -22,9 +22,14 @@ static int em_cmp_match(struct sk_buff *skb, struct tcf_ematch *em, > struct tcf_pkt_info *info) > { > struct tcf_em_cmp *cmp = (struct tcf_em_cmp *) em->data; > - unsigned char *ptr = tcf_get_base_ptr(skb, cmp->layer) + cmp->off; > + unsigned char *ptr; > u32 val = 0; > > + if (!cmp) > + return 0; It feels like this is papering over the real issue. Why em->data is NULL here? why other ematches are not afflicted by this issue?  is em->data really NULL or some small value instead? KASAN seams to tell it's a small value, not 0, so this patch should not avoid the oops. Have you tested it vs the reproducer? Thanks, Paolo