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| author | Eric Woudstra <ericwouds@gmail.com> | 2026-02-24 16:50:30 +0100 |
|---|---|---|
| committer | Jakub Kicinski <kuba@kernel.org> | 2026-02-25 19:25:08 -0800 |
| commit | 7717fbb14028be5735acb911aeb7553b7c662418 (patch) | |
| tree | 442fd021ae60fd99c48ec242e5a7277176dd3f6c | |
| parent | 8debe7a22309497f42fb963494833b9abd446328 (diff) | |
| download | lwn-7717fbb14028be5735acb911aeb7553b7c662418.tar.gz lwn-7717fbb14028be5735acb911aeb7553b7c662418.zip | |
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 <razor@blackwall.org>
Reviewed-by: Kees Cook <kees@kernel.org>
Signed-off-by: Eric Woudstra <ericwouds@gmail.com>
Link: https://patch.msgid.link/20260224155030.106918-1-ericwouds@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
| -rw-r--r-- | drivers/net/ppp/pppoe.c | 2 | ||||
| -rw-r--r-- | include/uapi/linux/if_pppox.h | 4 |
2 files changed, 5 insertions, 1 deletions
diff --git a/drivers/net/ppp/pppoe.c b/drivers/net/ppp/pppoe.c index 4275b393a454..7900cc3212a5 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 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 */ |