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[2a10:fc81:a806:d6a9::1]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-385eed2510esm8374572f8f.69.2024.12.03.15.42.29 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 03 Dec 2024 15:42:30 -0800 (PST) Date: Wed, 4 Dec 2024 00:42:28 +0100 From: Stefano Brivio To: Eric Dumazet Cc: "David S . Miller" , Jakub Kicinski , Paolo Abeni , netdev@vger.kernel.org, eric.dumazet@gmail.com, syzbot+3ec5271486d7cb2d242a@syzkaller.appspotmail.com Subject: Re: [PATCH net] geneve: do not assume mac header is set in geneve_xmit_skb() Message-ID: <20241204004228.0a18cfe6@elisabeth> In-Reply-To: <20241203182122.2725517-1-edumazet@google.com> References: <20241203182122.2725517-1-edumazet@google.com> Organization: Red Hat X-Mailer: Claws Mail 4.2.0 (GTK 3.24.41; x86_64-pc-linux-gnu) Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Hi, On Tue, 3 Dec 2024 18:21:21 +0000 Eric Dumazet wrote: > We should not assume mac header is set in output path. > > Use skb_eth_hdr() instead of eth_hdr() to fix the issue. > > sysbot reported the following : > > WARNING: CPU: 0 PID: 11635 at include/linux/skbuff.h:3052 skb_mac_header include/linux/skbuff.h:3052 [inline] > WARNING: CPU: 0 PID: 11635 at include/linux/skbuff.h:3052 eth_hdr include/linux/if_ether.h:24 [inline] > WARNING: CPU: 0 PID: 11635 at include/linux/skbuff.h:3052 geneve_xmit_skb drivers/net/geneve.c:898 [inline] > WARNING: CPU: 0 PID: 11635 at include/linux/skbuff.h:3052 geneve_xmit+0x4c38/0x5730 drivers/net/geneve.c:1039 > Modules linked in: > CPU: 0 UID: 0 PID: 11635 Comm: syz.4.1423 Not tainted 6.12.0-syzkaller-10296-gaaf20f870da0 #0 > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024 > RIP: 0010:skb_mac_header include/linux/skbuff.h:3052 [inline] > RIP: 0010:eth_hdr include/linux/if_ether.h:24 [inline] > RIP: 0010:geneve_xmit_skb drivers/net/geneve.c:898 [inline] > RIP: 0010:geneve_xmit+0x4c38/0x5730 drivers/net/geneve.c:1039 > Code: 21 c6 02 e9 35 d4 ff ff e8 a5 48 4c fb 90 0f 0b 90 e9 fd f5 ff ff e8 97 48 4c fb 90 0f 0b 90 e9 d8 f5 ff ff e8 89 48 4c fb 90 <0f> 0b 90 e9 41 e4 ff ff e8 7b 48 4c fb 90 0f 0b 90 e9 cd e7 ff ff > RSP: 0018:ffffc90003b2f870 EFLAGS: 00010283 > RAX: 000000000000037a RBX: 000000000000ffff RCX: ffffc9000dc3d000 > RDX: 0000000000080000 RSI: ffffffff86428417 RDI: 0000000000000003 > RBP: ffffc90003b2f9f0 R08: 0000000000000003 R09: 000000000000ffff > R10: 000000000000ffff R11: 0000000000000002 R12: ffff88806603c000 > R13: 0000000000000000 R14: ffff8880685b2780 R15: 0000000000000e23 > FS: 00007fdc2deed6c0(0000) GS:ffff8880b8600000(0000) knlGS:0000000000000000 > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > CR2: 0000001b30a1dff8 CR3: 0000000056b8c000 CR4: 00000000003526f0 > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 > Call Trace: > > __netdev_start_xmit include/linux/netdevice.h:5002 [inline] > netdev_start_xmit include/linux/netdevice.h:5011 [inline] > __dev_direct_xmit+0x58a/0x720 net/core/dev.c:4490 > dev_direct_xmit include/linux/netdevice.h:3181 [inline] > packet_xmit+0x1e4/0x360 net/packet/af_packet.c:285 > packet_snd net/packet/af_packet.c:3146 [inline] > packet_sendmsg+0x2700/0x5660 net/packet/af_packet.c:3178 > sock_sendmsg_nosec net/socket.c:711 [inline] > __sock_sendmsg net/socket.c:726 [inline] > __sys_sendto+0x488/0x4f0 net/socket.c:2197 > __do_sys_sendto net/socket.c:2204 [inline] > __se_sys_sendto net/socket.c:2200 [inline] > __x64_sys_sendto+0xe0/0x1c0 net/socket.c:2200 > do_syscall_x64 arch/x86/entry/common.c:52 [inline] > do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83 > entry_SYSCALL_64_after_hwframe+0x77/0x7f Oops. Thanks for looking into this. > Fixes: a025fb5f49ad ("geneve: Allow configuration of DF behaviour") > Reported-by: syzbot+3ec5271486d7cb2d242a@syzkaller.appspotmail.com > Closes: https://lore.kernel.org/netdev/674f4b72.050a0220.17bd51.004a.GAE@google.com/T/#u > Signed-off-by: Eric Dumazet > Cc: Stefano Brivio > --- > drivers/net/geneve.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/net/geneve.c b/drivers/net/geneve.c > index 2f29b1386b1c81640562e6ce91d6e8d88f0ffe1c..bc658bc6088546d5d1f116988b93d4dda915a799 100644 > --- a/drivers/net/geneve.c > +++ b/drivers/net/geneve.c > @@ -895,7 +895,7 @@ static int geneve_xmit_skb(struct sk_buff *skb, struct net_device *dev, > if (geneve->cfg.df == GENEVE_DF_SET) { > df = htons(IP_DF); > } else if (geneve->cfg.df == GENEVE_DF_INHERIT) { > - struct ethhdr *eth = eth_hdr(skb); > + struct ethhdr *eth = skb_eth_hdr(skb); Now, while your patch clearly looks better than the alternative, I wonder: if skb->mac_header is not set... > if (ntohs(eth->h_proto) == ETH_P_IPV6) { > df = htons(IP_DF); does eth->h_proto contain anything meaningful at this point? Is there a more robust way to check for the IP version of the encapsulated packet (assuming it's IP at all)? Or should we rather *not* touch 'df' at all if !skb_mac_header_was_set(skb)? Unless you have the answers, give me some time to check that. -- Stefano