From: Eric Woudstra Date: Tue, 24 Feb 2026 15:50:30 +0000 (+0100) Subject: net: pppoe: avoid zero-length arrays in struct pppoe_hdr X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=7717fbb14028be5735acb911aeb7553b7c662418;p=thirdparty%2Flinux.git net: pppoe: avoid zero-length arrays in struct pppoe_hdr Jakub Kicinski reported following issue in upcoming patches: W=1 C=1 GCC build gives us: net/bridge/netfilter/nf_conntrack_bridge.c: note: in included file (through ../include/linux/if_pppox.h, ../include/uapi/linux/netfilter_bridge.h, ../include/linux/netfilter_bridge.h): include/uapi/linux/if_pppox.h: 153:29: warning: array of flexible structures sparse doesn't like that hdr has a zero-length array which overlaps proto. The kernel code doesn't currently need those arrays. PPPoE connection is functional after applying this patch. Reviewed-by: Nikolay Aleksandrov Reviewed-by: Kees Cook Signed-off-by: Eric Woudstra Link: https://patch.msgid.link/20260224155030.106918-1-ericwouds@gmail.com Signed-off-by: Jakub Kicinski --- diff --git a/drivers/net/ppp/pppoe.c b/drivers/net/ppp/pppoe.c index 4275b393a4544..7900cc3212a58 100644 --- a/drivers/net/ppp/pppoe.c +++ b/drivers/net/ppp/pppoe.c @@ -885,7 +885,7 @@ static int pppoe_sendmsg(struct socket *sock, struct msghdr *m, skb->protocol = cpu_to_be16(ETH_P_PPP_SES); ph = skb_put(skb, total_len + sizeof(struct pppoe_hdr)); - start = (char *)&ph->tag[0]; + start = (char *)ph + sizeof(*ph); error = memcpy_from_msg(start, m, total_len); if (error < 0) { diff --git a/include/uapi/linux/if_pppox.h b/include/uapi/linux/if_pppox.h index 9abd80dcc46f9..29b804aa74745 100644 --- a/include/uapi/linux/if_pppox.h +++ b/include/uapi/linux/if_pppox.h @@ -122,7 +122,9 @@ struct sockaddr_pppol2tpv3in6 { struct pppoe_tag { __be16 tag_type; __be16 tag_len; +#ifndef __KERNEL__ char tag_data[]; +#endif } __attribute__ ((packed)); /* Tag identifiers */ @@ -150,7 +152,9 @@ struct pppoe_hdr { __u8 code; __be16 sid; __be16 length; +#ifndef __KERNEL__ struct pppoe_tag tag[]; +#endif } __packed; /* Length of entire PPPoE + PPP header */