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Tsirkin" To: Denis Arefev Cc: Jason Wang , Xuan Zhuo , Eugenio =?iso-8859-1?Q?P=E9rez?= , virtualization@lists.linux.dev, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, Eric Dumazet , lvc-project@linuxtesting.org Subject: Re: [PATCH v2] net: missing check virtio Message-ID: <20240619035015-mutt-send-email-mst@kernel.org> References: <20240613095448.27118-1-arefev@swemel.ru> 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-Disposition: inline In-Reply-To: <20240613095448.27118-1-arefev@swemel.ru> On Thu, Jun 13, 2024 at 12:54:48PM +0300, Denis Arefev wrote: > Two missing check in virtio_net_hdr_to_skb() allowed syzbot > to crash kernels again > > 1. After the skb_segment function the buffer may become non-linear > (nr_frags != 0), but since the SKBTX_SHARED_FRAG flag is not set anywhere > the __skb_linearize function will not be executed, then the buffer will > remain non-linear. Then the condition (offset >= skb_headlen(skb)) > becomes true, which causes WARN_ON_ONCE in skb_checksum_help. > > 2. The struct sk_buff and struct virtio_net_hdr members must be > mathematically related. > (gso_size) must be greater than (needed) otherwise WARN_ON_ONCE. > (remainder) must be greater than (needed) otherwise WARN_ON_ONCE. > (remainder) may be 0 if division is without remainder. > > offset+2 (4191) > skb_headlen() (1116) > WARNING: CPU: 1 PID: 5084 at net/core/dev.c:3303 skb_checksum_help+0x5e2/0x740 net/core/dev.c:3303 > Modules linked in: > CPU: 1 PID: 5084 Comm: syz-executor336 Not tainted 6.7.0-rc3-syzkaller-00014-gdf60cee26a2e #0 > Hardware name: Google Compute Engine/Google Compute Engine, BIOS Google 11/10/2023 > RIP: 0010:skb_checksum_help+0x5e2/0x740 net/core/dev.c:3303 > Code: 89 e8 83 e0 07 83 c0 03 38 d0 7c 08 84 d2 0f 85 52 01 00 00 44 89 e2 2b 53 74 4c 89 ee 48 c7 c7 40 57 e9 8b e8 af 8f dd f8 90 <0f> 0b 90 90 e9 87 fe ff ff e8 40 0f 6e f9 e9 4b fa ff ff 48 89 ef > RSP: 0018:ffffc90003a9f338 EFLAGS: 00010286 > RAX: 0000000000000000 RBX: ffff888025125780 RCX: ffffffff814db209 > RDX: ffff888015393b80 RSI: ffffffff814db216 RDI: 0000000000000001 > RBP: ffff8880251257f4 R08: 0000000000000001 R09: 0000000000000000 > R10: 0000000000000000 R11: 0000000000000001 R12: 000000000000045c > R13: 000000000000105f R14: ffff8880251257f0 R15: 000000000000105d > FS: 0000555555c24380(0000) GS:ffff8880b9900000(0000) knlGS:0000000000000000 > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > CR2: 000000002000f000 CR3: 0000000023151000 CR4: 00000000003506f0 > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 > Call Trace: > > ip_do_fragment+0xa1b/0x18b0 net/ipv4/ip_output.c:777 > ip_fragment.constprop.0+0x161/0x230 net/ipv4/ip_output.c:584 > ip_finish_output_gso net/ipv4/ip_output.c:286 [inline] > __ip_finish_output net/ipv4/ip_output.c:308 [inline] > __ip_finish_output+0x49c/0x650 net/ipv4/ip_output.c:295 > ip_finish_output+0x31/0x310 net/ipv4/ip_output.c:323 > NF_HOOK_COND include/linux/netfilter.h:303 [inline] > ip_output+0x13b/0x2a0 net/ipv4/ip_output.c:433 > dst_output include/net/dst.h:451 [inline] > ip_local_out+0xaf/0x1a0 net/ipv4/ip_output.c:129 > iptunnel_xmit+0x5b4/0x9b0 net/ipv4/ip_tunnel_core.c:82 > ipip6_tunnel_xmit net/ipv6/sit.c:1034 [inline] > sit_tunnel_xmit+0xed2/0x28f0 net/ipv6/sit.c:1076 > __netdev_start_xmit include/linux/netdevice.h:4940 [inline] > netdev_start_xmit include/linux/netdevice.h:4954 [inline] > xmit_one net/core/dev.c:3545 [inline] > dev_hard_start_xmit+0x13d/0x6d0 net/core/dev.c:3561 > __dev_queue_xmit+0x7c1/0x3d60 net/core/dev.c:4346 > dev_queue_xmit include/linux/netdevice.h:3134 [inline] > packet_xmit+0x257/0x380 net/packet/af_packet.c:276 > packet_snd net/packet/af_packet.c:3087 [inline] > packet_sendmsg+0x24ca/0x5240 net/packet/af_packet.c:3119 > sock_sendmsg_nosec net/socket.c:730 [inline] > __sock_sendmsg+0xd5/0x180 net/socket.c:745 > __sys_sendto+0x255/0x340 net/socket.c:2190 > __do_sys_sendto net/socket.c:2202 [inline] > __se_sys_sendto net/socket.c:2198 [inline] > __x64_sys_sendto+0xe0/0x1b0 net/socket.c:2198 > do_syscall_x64 arch/x86/entry/common.c:51 [inline] > do_syscall_64+0x40/0x110 arch/x86/entry/common.c:82 > entry_SYSCALL_64_after_hwframe+0x63/0x6b > > Found by Linux Verification Center (linuxtesting.org) with Syzkaller > > Signed-off-by: Denis Arefev > --- > V1 -> V2: incorrect type in argument 2 > include/linux/virtio_net.h | 11 +++++++++++ > 1 file changed, 11 insertions(+) > > diff --git a/include/linux/virtio_net.h b/include/linux/virtio_net.h > index 4dfa9b69ca8d..d1d7825318c3 100644 > --- a/include/linux/virtio_net.h > +++ b/include/linux/virtio_net.h > @@ -56,6 +56,7 @@ static inline int virtio_net_hdr_to_skb(struct sk_buff *skb, > unsigned int thlen = 0; > unsigned int p_off = 0; > unsigned int ip_proto; > + u64 ret, remainder, gso_size; > > if (hdr->gso_type != VIRTIO_NET_HDR_GSO_NONE) { > switch (hdr->gso_type & ~VIRTIO_NET_HDR_GSO_ECN) { > @@ -98,6 +99,16 @@ static inline int virtio_net_hdr_to_skb(struct sk_buff *skb, > u32 off = __virtio16_to_cpu(little_endian, hdr->csum_offset); > u32 needed = start + max_t(u32, thlen, off + sizeof(__sum16)); > > + if (hdr->gso_size) { > + gso_size = __virtio16_to_cpu(little_endian, hdr->gso_size); > + ret = div64_u64_rem(skb->len, gso_size, &remainder); > + if (!(ret && (hdr->gso_size > needed) && > + ((remainder > needed) || (remainder == 0)))) { > + return -EINVAL; > + } Could you please add some comments explaining the logic here? And do we really need u64 math? All the values here are 32 bit ATM ... > + skb_shinfo(skb)->tx_flags |= SKBFL_SHARED_FRAG; > + } > + > if (!pskb_may_pull(skb, needed)) > return -EINVAL; > > -- > 2.25.1