CVE-2026-90059 — net: stmmac: restore NET_IP_ALIGN in the RX DMA offset

Affected: Linux

In the Linux kernel, the following vulnerability has been resolved:

net: stmmac: restore NET_IP_ALIGN in the RX DMA offset

Since the RX path was converted to zero-copy, the page pool page is handed to the stack directly as the skb head, and the offset the DMA engine writes at is what determines the alignment of the packet headers.

Before the conversion the payload was copied into an skb obtained from napi_alloc_skb(), which reserves NET_SKB_PAD + NET_IP_ALIGN. The conversion moved the headroom into stmmac_rx_offset() but did not carry over NET_IP_ALIGN, so on architectures where NET_IP_ALIGN is 2 the IP header now lands misaligned:

64 (NET_SKB_PAD) + 14 (ethernet) + 20 (IP) = 98

Same for the XDP branch:

256 (XDP_PACKET_HEADROOM) + 14 (ethernet) + 20 (IP) = 290

On ARM32 this is fatal, because ldm and ldrd trap on unaligned addresses even when CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS is set.

Any received echo request panics the machine, e.g:

Unhandled fault: alignment exception (0x001) at 0x81873062 Internal error: : 1 [#1] SMP ARM Hardware name: Altera SOCFPGA Arria10 PC is at icmp_echo+0x38/0xa8 LR is at icmp_rcv+0x22c/0x370 Call trace: icmp_echo from icmp_rcv+0x22c/0x370 icmp_rcv from ip_protocol_deliver_rcu+0x2c/0x224 ip_protocol_deliver_rcu from ip_local_deliver+0xc8/0x1a0 ip_local_deliver from ip_sublist_rcv_finish+0x3c/0x50 ip_sublist_rcv_finish from ip_list_rcv_finish+0x110/0x118 ip_list_rcv_finish from ip_list_rcv+0xc8/0xdc…

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CVE-2026-90059 — net: stmmac: restore NET_IP_ALIGN in the RX DMA offset