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Message-ID: <ZaE39F93nKy4NKqj@nanopsycho>
Date: Fri, 12 Jan 2024 14:00:36 +0100
From: Jiri Pirko <jiri@...nulli.us>
To: Eric Dumazet <edumazet@...gle.com>
Cc: "David S . Miller" <davem@...emloft.net>,
Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
Willem de Bruijn <willemb@...gle.com>, netdev@...r.kernel.org,
eric.dumazet@...il.com,
syzbot+7f4d0ea3df4d4fa9a65f@...kaller.appspotmail.com
Subject: Re: [PATCH net] net: add more sanity check in virtio_net_hdr_to_skb()
Fri, Jan 12, 2024 at 01:28:16PM CET, edumazet@...gle.com wrote:
>syzbot/KMSAN reports access to uninitialized data from gso_features_check() [1]
>
>The repro use af_packet, injecting a gso packet and hdrlen == 0.
>
>We could fix the issue making gso_features_check() more careful
>while dealing with NETIF_F_TSO_MANGLEID in fast path.
>
>Or we can make sure virtio_net_hdr_to_skb() pulls minimal network and
>transport headers as intended.
You describe "either or", but don't really say what to do. Bit
confusing :/
>
>Note that for GSO packets coming from untrusted sources, SKB_GSO_DODGY
>bit forces a proper header validation (and pull) before the packet can
>hit any device ndo_start_xmit(), thus we do not need a precise disection
>at virtio_net_hdr_to_skb() stage.
>
>[1]
>BUG: KMSAN: uninit-value in skb_gso_segment include/net/gso.h:83 [inline]
>BUG: KMSAN: uninit-value in validate_xmit_skb+0x10f2/0x1930 net/core/dev.c:3629
> skb_gso_segment include/net/gso.h:83 [inline]
> validate_xmit_skb+0x10f2/0x1930 net/core/dev.c:3629
> __dev_queue_xmit+0x1eac/0x5130 net/core/dev.c:4341
> dev_queue_xmit include/linux/netdevice.h:3134 [inline]
> packet_xmit+0x9c/0x6b0 net/packet/af_packet.c:276
> packet_snd net/packet/af_packet.c:3087 [inline]
> packet_sendmsg+0x8b1d/0x9f30 net/packet/af_packet.c:3119
> sock_sendmsg_nosec net/socket.c:730 [inline]
> __sock_sendmsg net/socket.c:745 [inline]
> ____sys_sendmsg+0x9c2/0xd60 net/socket.c:2584
> ___sys_sendmsg+0x28d/0x3c0 net/socket.c:2638
> __sys_sendmsg net/socket.c:2667 [inline]
> __do_sys_sendmsg net/socket.c:2676 [inline]
> __se_sys_sendmsg net/socket.c:2674 [inline]
> __x64_sys_sendmsg+0x307/0x490 net/socket.c:2674
> do_syscall_x64 arch/x86/entry/common.c:52 [inline]
> do_syscall_64+0x44/0x110 arch/x86/entry/common.c:83
> entry_SYSCALL_64_after_hwframe+0x63/0x6b
>
>Uninit was created at:
> slab_post_alloc_hook+0x129/0xa70 mm/slab.h:768
> slab_alloc_node mm/slub.c:3478 [inline]
> kmem_cache_alloc_node+0x5e9/0xb10 mm/slub.c:3523
> kmalloc_reserve+0x13d/0x4a0 net/core/skbuff.c:560
> __alloc_skb+0x318/0x740 net/core/skbuff.c:651
> alloc_skb include/linux/skbuff.h:1286 [inline]
> alloc_skb_with_frags+0xc8/0xbd0 net/core/skbuff.c:6334
> sock_alloc_send_pskb+0xa80/0xbf0 net/core/sock.c:2780
> packet_alloc_skb net/packet/af_packet.c:2936 [inline]
> packet_snd net/packet/af_packet.c:3030 [inline]
> packet_sendmsg+0x70e8/0x9f30 net/packet/af_packet.c:3119
> sock_sendmsg_nosec net/socket.c:730 [inline]
> __sock_sendmsg net/socket.c:745 [inline]
> ____sys_sendmsg+0x9c2/0xd60 net/socket.c:2584
> ___sys_sendmsg+0x28d/0x3c0 net/socket.c:2638
> __sys_sendmsg net/socket.c:2667 [inline]
> __do_sys_sendmsg net/socket.c:2676 [inline]
> __se_sys_sendmsg net/socket.c:2674 [inline]
> __x64_sys_sendmsg+0x307/0x490 net/socket.c:2674
> do_syscall_x64 arch/x86/entry/common.c:52 [inline]
> do_syscall_64+0x44/0x110 arch/x86/entry/common.c:83
> entry_SYSCALL_64_after_hwframe+0x63/0x6b
>
>CPU: 0 PID: 5025 Comm: syz-executor279 Not tainted 6.7.0-rc7-syzkaller-00003-gfbafc3e621c3 #0
>Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/17/2023
>
>Reported-by: syzbot+7f4d0ea3df4d4fa9a65f@...kaller.appspotmail.com
>Link: https://lore.kernel.org/netdev/0000000000005abd7b060eb160cd@google.com/
>Fixes: 9274124f023b ("net: stricter validation of untrusted gso packets")
>Signed-off-by: Eric Dumazet <edumazet@...gle.com>
>Cc: Willem de Bruijn <willemb@...gle.com>
>---
> include/linux/virtio_net.h | 9 +++++++--
> 1 file changed, 7 insertions(+), 2 deletions(-)
>
>diff --git a/include/linux/virtio_net.h b/include/linux/virtio_net.h
>index 27cc1d4643219a44c01a2404124cd45ef46f7f3d..4dfa9b69ca8d95d43e44831bc166eadbe5715d3c 100644
>--- a/include/linux/virtio_net.h
>+++ b/include/linux/virtio_net.h
>@@ -3,6 +3,8 @@
> #define _LINUX_VIRTIO_NET_H
>
> #include <linux/if_vlan.h>
>+#include <linux/ip.h>
>+#include <linux/ipv6.h>
> #include <linux/udp.h>
> #include <uapi/linux/tcp.h>
> #include <uapi/linux/virtio_net.h>
>@@ -49,6 +51,7 @@ static inline int virtio_net_hdr_to_skb(struct sk_buff *skb,
> const struct virtio_net_hdr *hdr,
> bool little_endian)
> {
>+ unsigned int nh_min_len = sizeof(struct iphdr);
> unsigned int gso_type = 0;
> unsigned int thlen = 0;
> unsigned int p_off = 0;
>@@ -65,6 +68,7 @@ static inline int virtio_net_hdr_to_skb(struct sk_buff *skb,
> gso_type = SKB_GSO_TCPV6;
> ip_proto = IPPROTO_TCP;
> thlen = sizeof(struct tcphdr);
>+ nh_min_len = sizeof(struct ipv6hdr);
> break;
> case VIRTIO_NET_HDR_GSO_UDP:
> gso_type = SKB_GSO_UDP;
>@@ -100,7 +104,8 @@ static inline int virtio_net_hdr_to_skb(struct sk_buff *skb,
> if (!skb_partial_csum_set(skb, start, off))
> return -EINVAL;
>
>- p_off = skb_transport_offset(skb) + thlen;
>+ nh_min_len = max_t(u32, nh_min_len, skb_transport_offset(skb));
>+ p_off = nh_min_len + thlen;
> if (!pskb_may_pull(skb, p_off))
> return -EINVAL;
> } else {
>@@ -140,7 +145,7 @@ static inline int virtio_net_hdr_to_skb(struct sk_buff *skb,
>
> skb_set_transport_header(skb, keys.control.thoff);
> } else if (gso_type) {
>- p_off = thlen;
>+ p_off = nh_min_len + thlen;
> if (!pskb_may_pull(skb, p_off))
> return -EINVAL;
> }
>--
>2.43.0.275.g3460e3d667-goog
>
>
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