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[2001:1c00:20d:1300:1b1c:4449:176a:89ea]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-ac7c1db6ea1sm928770066b.143.2025.04.08.07.24.41 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 08 Apr 2025 07:24:42 -0700 (PDT) From: Eric Woudstra To: Michal Ostrowski , Andrew Lunn , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Pablo Neira Ayuso , Jozsef Kadlecsik , Simon Horman , Nikolay Aleksandrov Cc: netdev@vger.kernel.org, netfilter-devel@vger.kernel.org, linux-hardening@vger.kernel.org, Eric Woudstra Subject: [PATCH v11 nf-next 1/2] net: pppoe: avoid zero-length arrays in struct pppoe_hdr Date: Tue, 8 Apr 2025 16:24:24 +0200 Message-ID: <20250408142425.95437-2-ericwouds@gmail.com> X-Mailer: git-send-email 2.47.1 In-Reply-To: <20250408142425.95437-1-ericwouds@gmail.com> References: <20250408142425.95437-1-ericwouds@gmail.com> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Jakub Kicinski suggested following patch: 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 It 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 Signed-off-by: Eric Woudstra --- drivers/net/ppp/pppoe.c | 2 +- include/uapi/linux/if_pppox.h | 4 ++++ 2 files changed, 5 insertions(+), 1 deletion(-) diff --git a/drivers/net/ppp/pppoe.c b/drivers/net/ppp/pppoe.c index 68e631718ab0..17946af6a8cf 100644 --- a/drivers/net/ppp/pppoe.c +++ b/drivers/net/ppp/pppoe.c @@ -882,7 +882,7 @@ 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 9abd80dcc46f..29b804aa7474 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 */ -- 2.47.1