* [PATCH net v3] net: drop UFO packets in udp_rcv_segment()
@ 2025-07-30 10:14 Wang Liang
2025-07-30 16:47 ` Willem de Bruijn
2025-08-02 0:30 ` patchwork-bot+netdevbpf
0 siblings, 2 replies; 3+ messages in thread
From: Wang Liang @ 2025-07-30 10:14 UTC (permalink / raw)
To: willemdebruijn.kernel, davem, edumazet, kuba, pabeni, horms
Cc: yuehaibing, zhangchangzhong, wangliang74, netdev, linux-kernel
When sending a packet with virtio_net_hdr to tun device, if the gso_type
in virtio_net_hdr is SKB_GSO_UDP and the gso_size is less than udphdr
size, below crash may happen.
------------[ cut here ]------------
kernel BUG at net/core/skbuff.c:4572!
Oops: invalid opcode: 0000 [#1] SMP NOPTI
CPU: 0 UID: 0 PID: 62 Comm: mytest Not tainted 6.16.0-rc7 #203 PREEMPT(voluntary)
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1 04/01/2014
RIP: 0010:skb_pull_rcsum+0x8e/0xa0
Code: 00 00 5b c3 cc cc cc cc 8b 93 88 00 00 00 f7 da e8 37 44 38 00 f7 d8 89 83 88 00 00 00 48 8b 83 c8 00 00 00 5b c3 cc cc cc cc <0f> 0b 0f 0b 66 66 2e 0f 1f 84 00 000
RSP: 0018:ffffc900001fba38 EFLAGS: 00000297
RAX: 0000000000000004 RBX: ffff8880040c1000 RCX: ffffc900001fb948
RDX: ffff888003e6d700 RSI: 0000000000000008 RDI: ffff88800411a062
RBP: ffff8880040c1000 R08: 0000000000000000 R09: 0000000000000001
R10: ffff888003606c00 R11: 0000000000000001 R12: 0000000000000000
R13: ffff888004060900 R14: ffff888004050000 R15: ffff888004060900
FS: 000000002406d3c0(0000) GS:ffff888084a19000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000020000040 CR3: 0000000004007000 CR4: 00000000000006f0
Call Trace:
<TASK>
udp_queue_rcv_one_skb+0x176/0x4b0 net/ipv4/udp.c:2445
udp_queue_rcv_skb+0x155/0x1f0 net/ipv4/udp.c:2475
udp_unicast_rcv_skb+0x71/0x90 net/ipv4/udp.c:2626
__udp4_lib_rcv+0x433/0xb00 net/ipv4/udp.c:2690
ip_protocol_deliver_rcu+0xa6/0x160 net/ipv4/ip_input.c:205
ip_local_deliver_finish+0x72/0x90 net/ipv4/ip_input.c:233
ip_sublist_rcv_finish+0x5f/0x70 net/ipv4/ip_input.c:579
ip_sublist_rcv+0x122/0x1b0 net/ipv4/ip_input.c:636
ip_list_rcv+0xf7/0x130 net/ipv4/ip_input.c:670
__netif_receive_skb_list_core+0x21d/0x240 net/core/dev.c:6067
netif_receive_skb_list_internal+0x186/0x2b0 net/core/dev.c:6210
napi_complete_done+0x78/0x180 net/core/dev.c:6580
tun_get_user+0xa63/0x1120 drivers/net/tun.c:1909
tun_chr_write_iter+0x65/0xb0 drivers/net/tun.c:1984
vfs_write+0x300/0x420 fs/read_write.c:593
ksys_write+0x60/0xd0 fs/read_write.c:686
do_syscall_64+0x50/0x1c0 arch/x86/entry/syscall_64.c:63
</TASK>
To trigger gso segment in udp_queue_rcv_skb(), we should also set option
UDP_ENCAP_ESPINUDP to enable udp_sk(sk)->encap_rcv. When the encap_rcv
hook return 1 in udp_queue_rcv_one_skb(), udp_csum_pull_header() will try
to pull udphdr, but the skb size has been segmented to gso size, which
leads to this crash.
Previous commit cf329aa42b66 ("udp: cope with UDP GRO packet misdirection")
introduces segmentation in UDP receive path only for GRO, which was never
intended to be used for UFO, so drop UFO packets in udp_rcv_segment().
Link: https://lore.kernel.org/netdev/20250724083005.3918375-1-wangliang74@huawei.com/
Link: https://lore.kernel.org/netdev/20250729123907.3318425-1-wangliang74@huawei.com/
Fixes: cf329aa42b66 ("udp: cope with UDP GRO packet misdirection")
Suggested-by: Willem de Bruijn <willemdebruijn.kernel@gmail.com>
Signed-off-by: Wang Liang <wangliang74@huawei.com>
---
Changes in v2:
- drop UFO packets instead of checking min gso size.
Changes in v3:
- rename commit to limit the drop packets type.
- modify fix tag.
- only drop SKB_GSO_UDP packets, keep SKB_GSO_UDP_L4 packets.
---
include/net/udp.h | 24 ++++++++++++++++++------
1 file changed, 18 insertions(+), 6 deletions(-)
diff --git a/include/net/udp.h b/include/net/udp.h
index a772510b2aa5..7a4524243b19 100644
--- a/include/net/udp.h
+++ b/include/net/udp.h
@@ -587,6 +587,16 @@ static inline struct sk_buff *udp_rcv_segment(struct sock *sk,
{
netdev_features_t features = NETIF_F_SG;
struct sk_buff *segs;
+ int drop_count;
+
+ /*
+ * Segmentation in UDP receive path is only for UDP GRO, drop udp
+ * fragmentation offload (UFO) packets.
+ */
+ if (skb_shinfo(skb)->gso_type & SKB_GSO_UDP) {
+ drop_count = 1;
+ goto drop;
+ }
/* Avoid csum recalculation by skb_segment unless userspace explicitly
* asks for the final checksum values
@@ -610,16 +620,18 @@ static inline struct sk_buff *udp_rcv_segment(struct sock *sk,
*/
segs = __skb_gso_segment(skb, features, false);
if (IS_ERR_OR_NULL(segs)) {
- int segs_nr = skb_shinfo(skb)->gso_segs;
-
- atomic_add(segs_nr, &sk->sk_drops);
- SNMP_ADD_STATS(__UDPX_MIB(sk, ipv4), UDP_MIB_INERRORS, segs_nr);
- kfree_skb(skb);
- return NULL;
+ drop_count = skb_shinfo(skb)->gso_segs;
+ goto drop;
}
consume_skb(skb);
return segs;
+
+drop:
+ atomic_add(drop_count, &sk->sk_drops);
+ SNMP_ADD_STATS(__UDPX_MIB(sk, ipv4), UDP_MIB_INERRORS, drop_count);
+ kfree_skb(skb);
+ return NULL;
}
static inline void udp_post_segment_fix_csum(struct sk_buff *skb)
--
2.34.1
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH net v3] net: drop UFO packets in udp_rcv_segment()
2025-07-30 10:14 [PATCH net v3] net: drop UFO packets in udp_rcv_segment() Wang Liang
@ 2025-07-30 16:47 ` Willem de Bruijn
2025-08-02 0:30 ` patchwork-bot+netdevbpf
1 sibling, 0 replies; 3+ messages in thread
From: Willem de Bruijn @ 2025-07-30 16:47 UTC (permalink / raw)
To: Wang Liang, willemdebruijn.kernel, davem, edumazet, kuba, pabeni,
horms
Cc: yuehaibing, zhangchangzhong, wangliang74, netdev, linux-kernel
Wang Liang wrote:
> When sending a packet with virtio_net_hdr to tun device, if the gso_type
> in virtio_net_hdr is SKB_GSO_UDP and the gso_size is less than udphdr
> size, below crash may happen.
>
> ------------[ cut here ]------------
> kernel BUG at net/core/skbuff.c:4572!
> Oops: invalid opcode: 0000 [#1] SMP NOPTI
> CPU: 0 UID: 0 PID: 62 Comm: mytest Not tainted 6.16.0-rc7 #203 PREEMPT(voluntary)
> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1 04/01/2014
> RIP: 0010:skb_pull_rcsum+0x8e/0xa0
> Code: 00 00 5b c3 cc cc cc cc 8b 93 88 00 00 00 f7 da e8 37 44 38 00 f7 d8 89 83 88 00 00 00 48 8b 83 c8 00 00 00 5b c3 cc cc cc cc <0f> 0b 0f 0b 66 66 2e 0f 1f 84 00 000
> RSP: 0018:ffffc900001fba38 EFLAGS: 00000297
> RAX: 0000000000000004 RBX: ffff8880040c1000 RCX: ffffc900001fb948
> RDX: ffff888003e6d700 RSI: 0000000000000008 RDI: ffff88800411a062
> RBP: ffff8880040c1000 R08: 0000000000000000 R09: 0000000000000001
> R10: ffff888003606c00 R11: 0000000000000001 R12: 0000000000000000
> R13: ffff888004060900 R14: ffff888004050000 R15: ffff888004060900
> FS: 000000002406d3c0(0000) GS:ffff888084a19000(0000) knlGS:0000000000000000
> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 0000000020000040 CR3: 0000000004007000 CR4: 00000000000006f0
> Call Trace:
> <TASK>
> udp_queue_rcv_one_skb+0x176/0x4b0 net/ipv4/udp.c:2445
> udp_queue_rcv_skb+0x155/0x1f0 net/ipv4/udp.c:2475
> udp_unicast_rcv_skb+0x71/0x90 net/ipv4/udp.c:2626
> __udp4_lib_rcv+0x433/0xb00 net/ipv4/udp.c:2690
> ip_protocol_deliver_rcu+0xa6/0x160 net/ipv4/ip_input.c:205
> ip_local_deliver_finish+0x72/0x90 net/ipv4/ip_input.c:233
> ip_sublist_rcv_finish+0x5f/0x70 net/ipv4/ip_input.c:579
> ip_sublist_rcv+0x122/0x1b0 net/ipv4/ip_input.c:636
> ip_list_rcv+0xf7/0x130 net/ipv4/ip_input.c:670
> __netif_receive_skb_list_core+0x21d/0x240 net/core/dev.c:6067
> netif_receive_skb_list_internal+0x186/0x2b0 net/core/dev.c:6210
> napi_complete_done+0x78/0x180 net/core/dev.c:6580
> tun_get_user+0xa63/0x1120 drivers/net/tun.c:1909
> tun_chr_write_iter+0x65/0xb0 drivers/net/tun.c:1984
> vfs_write+0x300/0x420 fs/read_write.c:593
> ksys_write+0x60/0xd0 fs/read_write.c:686
> do_syscall_64+0x50/0x1c0 arch/x86/entry/syscall_64.c:63
> </TASK>
>
> To trigger gso segment in udp_queue_rcv_skb(), we should also set option
> UDP_ENCAP_ESPINUDP to enable udp_sk(sk)->encap_rcv. When the encap_rcv
> hook return 1 in udp_queue_rcv_one_skb(), udp_csum_pull_header() will try
> to pull udphdr, but the skb size has been segmented to gso size, which
> leads to this crash.
>
> Previous commit cf329aa42b66 ("udp: cope with UDP GRO packet misdirection")
> introduces segmentation in UDP receive path only for GRO, which was never
> intended to be used for UFO, so drop UFO packets in udp_rcv_segment().
>
> Link: https://lore.kernel.org/netdev/20250724083005.3918375-1-wangliang74@huawei.com/
> Link: https://lore.kernel.org/netdev/20250729123907.3318425-1-wangliang74@huawei.com/
> Fixes: cf329aa42b66 ("udp: cope with UDP GRO packet misdirection")
> Suggested-by: Willem de Bruijn <willemdebruijn.kernel@gmail.com>
> Signed-off-by: Wang Liang <wangliang74@huawei.com>
Reviewed-by: Willem de Bruijn <willemb@google.com>
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH net v3] net: drop UFO packets in udp_rcv_segment()
2025-07-30 10:14 [PATCH net v3] net: drop UFO packets in udp_rcv_segment() Wang Liang
2025-07-30 16:47 ` Willem de Bruijn
@ 2025-08-02 0:30 ` patchwork-bot+netdevbpf
1 sibling, 0 replies; 3+ messages in thread
From: patchwork-bot+netdevbpf @ 2025-08-02 0:30 UTC (permalink / raw)
To: Wang Liang
Cc: willemdebruijn.kernel, davem, edumazet, kuba, pabeni, horms,
yuehaibing, zhangchangzhong, netdev, linux-kernel
Hello:
This patch was applied to netdev/net.git (main)
by Jakub Kicinski <kuba@kernel.org>:
On Wed, 30 Jul 2025 18:14:58 +0800 you wrote:
> When sending a packet with virtio_net_hdr to tun device, if the gso_type
> in virtio_net_hdr is SKB_GSO_UDP and the gso_size is less than udphdr
> size, below crash may happen.
>
> ------------[ cut here ]------------
> kernel BUG at net/core/skbuff.c:4572!
> Oops: invalid opcode: 0000 [#1] SMP NOPTI
> CPU: 0 UID: 0 PID: 62 Comm: mytest Not tainted 6.16.0-rc7 #203 PREEMPT(voluntary)
> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1 04/01/2014
> RIP: 0010:skb_pull_rcsum+0x8e/0xa0
> Code: 00 00 5b c3 cc cc cc cc 8b 93 88 00 00 00 f7 da e8 37 44 38 00 f7 d8 89 83 88 00 00 00 48 8b 83 c8 00 00 00 5b c3 cc cc cc cc <0f> 0b 0f 0b 66 66 2e 0f 1f 84 00 000
> RSP: 0018:ffffc900001fba38 EFLAGS: 00000297
> RAX: 0000000000000004 RBX: ffff8880040c1000 RCX: ffffc900001fb948
> RDX: ffff888003e6d700 RSI: 0000000000000008 RDI: ffff88800411a062
> RBP: ffff8880040c1000 R08: 0000000000000000 R09: 0000000000000001
> R10: ffff888003606c00 R11: 0000000000000001 R12: 0000000000000000
> R13: ffff888004060900 R14: ffff888004050000 R15: ffff888004060900
> FS: 000000002406d3c0(0000) GS:ffff888084a19000(0000) knlGS:0000000000000000
> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 0000000020000040 CR3: 0000000004007000 CR4: 00000000000006f0
> Call Trace:
> <TASK>
> udp_queue_rcv_one_skb+0x176/0x4b0 net/ipv4/udp.c:2445
> udp_queue_rcv_skb+0x155/0x1f0 net/ipv4/udp.c:2475
> udp_unicast_rcv_skb+0x71/0x90 net/ipv4/udp.c:2626
> __udp4_lib_rcv+0x433/0xb00 net/ipv4/udp.c:2690
> ip_protocol_deliver_rcu+0xa6/0x160 net/ipv4/ip_input.c:205
> ip_local_deliver_finish+0x72/0x90 net/ipv4/ip_input.c:233
> ip_sublist_rcv_finish+0x5f/0x70 net/ipv4/ip_input.c:579
> ip_sublist_rcv+0x122/0x1b0 net/ipv4/ip_input.c:636
> ip_list_rcv+0xf7/0x130 net/ipv4/ip_input.c:670
> __netif_receive_skb_list_core+0x21d/0x240 net/core/dev.c:6067
> netif_receive_skb_list_internal+0x186/0x2b0 net/core/dev.c:6210
> napi_complete_done+0x78/0x180 net/core/dev.c:6580
> tun_get_user+0xa63/0x1120 drivers/net/tun.c:1909
> tun_chr_write_iter+0x65/0xb0 drivers/net/tun.c:1984
> vfs_write+0x300/0x420 fs/read_write.c:593
> ksys_write+0x60/0xd0 fs/read_write.c:686
> do_syscall_64+0x50/0x1c0 arch/x86/entry/syscall_64.c:63
> </TASK>
>
> [...]
Here is the summary with links:
- [net,v3] net: drop UFO packets in udp_rcv_segment()
https://git.kernel.org/netdev/net/c/d46e51f1c78b
You are awesome, thank you!
--
Deet-doot-dot, I am a bot.
https://korg.docs.kernel.org/patchwork/pwbot.html
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2025-07-30 10:14 [PATCH net v3] net: drop UFO packets in udp_rcv_segment() Wang Liang
2025-07-30 16:47 ` Willem de Bruijn
2025-08-02 0:30 ` patchwork-bot+netdevbpf
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