From: Eric Dumazet edumazet@google.com
commit 9181d6f8a2bb32d158de66a84164fac05e3ddd18 upstream.
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.
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@syzkaller.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@google.com Cc: Willem de Bruijn willemb@google.com Reviewed-by: Willem de Bruijn willemb@google.com Signed-off-by: David S. Miller davem@davemloft.net [Denis: minor fix to resolve merge conflict.] Signed-off-by: Denis Arefev arefev@swemel.ru --- Backport fix for CVE-2024-43817 Link: https://nvd.nist.gov/vuln/detail/cve-2024-43817 --- 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 62613d4d84b7..e9e681fab607 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> @@ -47,6 +49,7 @@ 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; @@ -63,6 +66,7 @@ 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; @@ -93,7 +97,8 @@ 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 { @@ -133,7 +138,7 @@ 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; }