CVE-2026-80742af_packet: Don't send zero-byte data in tpacket_snd().

Official description

In the Linux kernel, the following vulnerability has been resolved: af_packet: Don't send zero-byte data in tpacket_snd(). syzbot reported a WARNING in __dev_queue_xmit() triggered via tpacket_snd(): skb_assert_len WARNING: at include/linux/skbuff.h:2753 skb_assert_len WARNING: at __dev_queue_xmit+0x21bc/0x4970 net/core/dev.c:4781 Call Trace: <TASK> dev_queue_xmit include/linux/netdevice.h:3448 [inline] packet_xmit+0x243/0x310 net/packet/af_packet.c:276 tpacket_snd net/packet/af_packet.c:2907 [inline] packet_sendmsg+0x28d6/0x4eb0 net/packet/af_packet.c:3134 When sending 0-byte packets via TPACKET ring buffer on devices with no hard header (e.g. dev->hard_header_len == 0), tpacket_fill_skb() populates an skb with skb->len == 0 and returns 0. tpacket_snd() then forwards this empty skb to packet_xmit(), causing __dev_queue_xmit() to hit skb_assert_len(skb). Similar checks exist in packet_snd() via commit dc633700f00f ("net/af_packet: check len when min_header_len equals to 0") and in packet_sendmsg_spkt() via commit 6a341729fb31 ("af_packet: Don't send zero-byte data in packet_sendmsg_spkt()."). Return -EINVAL in tpacket_fill_skb() when skb->len is zero to reject zero-length packets in tpacket_snd().

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/dde212f8622f5cb36223fff1ebd6e6f2a3dc61fe
• https://git.kernel.org/stable/c/80a702964467b998d254f16cc61c2c9a20540c9d
• https://git.kernel.org/stable/c/7521e691c7c4f2231634c95053281ac888d1f452
• https://git.kernel.org/stable/c/1fc70b3d513bafb16b17540178870ef46e81c0bb
• https://git.kernel.org/stable/c/3fa110f9e2ea96f567f2194c673c4bc327640111
• https://git.kernel.org/stable/c/98c5914d6b7bd4b4675535908e57dea31f1efd6a
• https://git.kernel.org/stable/c/f09ac5682f1bb67981fcb6ead4d3cfe439225876
• https://git.kernel.org/stable/c/6bcd76c134c55c697148acb5c0194e9666abdf84