From 1bc46dd209667346c5aa56c351995e7c260696d0 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Fri, 30 Jan 2026 21:02:56 +0000 Subject: [PATCH] ipv6: pass proto by value to ipv6_push_nfrag_opts() and ipv6_push_frag_opts() With CONFIG_STACKPROTECTOR_STRONG=y, it is better to avoid passing a pointer to an automatic variable. Change these exported functions to return 'u8 proto' instead of void. - ipv6_push_nfrag_opts() - ipv6_push_frag_opts() For instance, replace ipv6_push_frag_opts(skb, opt, &proto); with: proto = ipv6_push_frag_opts(skb, opt, proto); Note that even after this change, ip6_xmit() has to use a stack canary because of @first_hop variable. Signed-off-by: Eric Dumazet Reviewed-by: Kuniyuki Iwashima Link: https://patch.msgid.link/20260130210303.3888261-2-edumazet@google.com Signed-off-by: Jakub Kicinski --- include/net/ipv6.h | 10 ++++---- net/ipv6/exthdrs.c | 55 +++++++++++++++++++++++-------------------- net/ipv6/ip6_output.c | 19 ++++++++------- net/ipv6/ip6_tunnel.c | 2 +- 4 files changed, 46 insertions(+), 40 deletions(-) diff --git a/include/net/ipv6.h b/include/net/ipv6.h index cf2203ff2bfd2..a35f0a8114c09 100644 --- a/include/net/ipv6.h +++ b/include/net/ipv6.h @@ -1151,11 +1151,11 @@ int ip6_local_out(struct net *net, struct sock *sk, struct sk_buff *skb); * Extension header (options) processing */ -void ipv6_push_nfrag_opts(struct sk_buff *skb, struct ipv6_txoptions *opt, - u8 *proto, struct in6_addr **daddr_p, - struct in6_addr *saddr); -void ipv6_push_frag_opts(struct sk_buff *skb, struct ipv6_txoptions *opt, - u8 *proto); +u8 ipv6_push_nfrag_opts(struct sk_buff *skb, struct ipv6_txoptions *opt, + u8 proto, struct in6_addr **daddr_p, + struct in6_addr *saddr); +u8 ipv6_push_frag_opts(struct sk_buff *skb, struct ipv6_txoptions *opt, + u8 proto); int ipv6_skip_exthdr(const struct sk_buff *, int start, u8 *nexthdrp, __be16 *frag_offp); diff --git a/net/ipv6/exthdrs.c b/net/ipv6/exthdrs.c index cd318ff0dcd87..209fdf1b1aa9b 100644 --- a/net/ipv6/exthdrs.c +++ b/net/ipv6/exthdrs.c @@ -1074,9 +1074,9 @@ fail_and_free: * for headers. */ -static void ipv6_push_rthdr0(struct sk_buff *skb, u8 *proto, - struct ipv6_rt_hdr *opt, - struct in6_addr **addr_p, struct in6_addr *saddr) +static u8 ipv6_push_rthdr0(struct sk_buff *skb, u8 proto, + struct ipv6_rt_hdr *opt, + struct in6_addr **addr_p, struct in6_addr *saddr) { struct rt0_hdr *phdr, *ihdr; int hops; @@ -1095,13 +1095,13 @@ static void ipv6_push_rthdr0(struct sk_buff *skb, u8 *proto, phdr->addr[hops - 1] = **addr_p; *addr_p = ihdr->addr; - phdr->rt_hdr.nexthdr = *proto; - *proto = NEXTHDR_ROUTING; + phdr->rt_hdr.nexthdr = proto; + return NEXTHDR_ROUTING; } -static void ipv6_push_rthdr4(struct sk_buff *skb, u8 *proto, - struct ipv6_rt_hdr *opt, - struct in6_addr **addr_p, struct in6_addr *saddr) +static u8 ipv6_push_rthdr4(struct sk_buff *skb, u8 proto, + struct ipv6_rt_hdr *opt, + struct in6_addr **addr_p, struct in6_addr *saddr) { struct ipv6_sr_hdr *sr_phdr, *sr_ihdr; int plen, hops; @@ -1144,58 +1144,61 @@ static void ipv6_push_rthdr4(struct sk_buff *skb, u8 *proto, } #endif - sr_phdr->nexthdr = *proto; - *proto = NEXTHDR_ROUTING; + sr_phdr->nexthdr = proto; + return NEXTHDR_ROUTING; } -static void ipv6_push_rthdr(struct sk_buff *skb, u8 *proto, - struct ipv6_rt_hdr *opt, - struct in6_addr **addr_p, struct in6_addr *saddr) +static u8 ipv6_push_rthdr(struct sk_buff *skb, u8 proto, + struct ipv6_rt_hdr *opt, + struct in6_addr **addr_p, struct in6_addr *saddr) { switch (opt->type) { case IPV6_SRCRT_TYPE_0: case IPV6_SRCRT_STRICT: case IPV6_SRCRT_TYPE_2: - ipv6_push_rthdr0(skb, proto, opt, addr_p, saddr); + proto = ipv6_push_rthdr0(skb, proto, opt, addr_p, saddr); break; case IPV6_SRCRT_TYPE_4: - ipv6_push_rthdr4(skb, proto, opt, addr_p, saddr); + proto = ipv6_push_rthdr4(skb, proto, opt, addr_p, saddr); break; default: break; } + return proto; } -static void ipv6_push_exthdr(struct sk_buff *skb, u8 *proto, u8 type, struct ipv6_opt_hdr *opt) +static u8 ipv6_push_exthdr(struct sk_buff *skb, u8 proto, u8 type, struct ipv6_opt_hdr *opt) { struct ipv6_opt_hdr *h = skb_push(skb, ipv6_optlen(opt)); memcpy(h, opt, ipv6_optlen(opt)); - h->nexthdr = *proto; - *proto = type; + h->nexthdr = proto; + return type; } -void ipv6_push_nfrag_opts(struct sk_buff *skb, struct ipv6_txoptions *opt, - u8 *proto, - struct in6_addr **daddr, struct in6_addr *saddr) +u8 ipv6_push_nfrag_opts(struct sk_buff *skb, struct ipv6_txoptions *opt, + u8 proto, + struct in6_addr **daddr, struct in6_addr *saddr) { if (opt->srcrt) { - ipv6_push_rthdr(skb, proto, opt->srcrt, daddr, saddr); + proto = ipv6_push_rthdr(skb, proto, opt->srcrt, daddr, saddr); /* * IPV6_RTHDRDSTOPTS is ignored * unless IPV6_RTHDR is set (RFC3542). */ if (opt->dst0opt) - ipv6_push_exthdr(skb, proto, NEXTHDR_DEST, opt->dst0opt); + proto = ipv6_push_exthdr(skb, proto, NEXTHDR_DEST, opt->dst0opt); } if (opt->hopopt) - ipv6_push_exthdr(skb, proto, NEXTHDR_HOP, opt->hopopt); + proto = ipv6_push_exthdr(skb, proto, NEXTHDR_HOP, opt->hopopt); + return proto; } -void ipv6_push_frag_opts(struct sk_buff *skb, struct ipv6_txoptions *opt, u8 *proto) +u8 ipv6_push_frag_opts(struct sk_buff *skb, struct ipv6_txoptions *opt, u8 proto) { if (opt->dst1opt) - ipv6_push_exthdr(skb, proto, NEXTHDR_DEST, opt->dst1opt); + proto = ipv6_push_exthdr(skb, proto, NEXTHDR_DEST, opt->dst1opt); + return proto; } EXPORT_SYMBOL(ipv6_push_frag_opts); diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c index f904739e99b90..e4bed95ae5bba 100644 --- a/net/ipv6/ip6_output.c +++ b/net/ipv6/ip6_output.c @@ -305,11 +305,12 @@ int ip6_xmit(const struct sock *sk, struct sk_buff *skb, struct flowi6 *fl6, seg_len += opt->opt_nflen + opt->opt_flen; if (opt->opt_flen) - ipv6_push_frag_opts(skb, opt, &proto); + proto = ipv6_push_frag_opts(skb, opt, proto); if (opt->opt_nflen) - ipv6_push_nfrag_opts(skb, opt, &proto, &first_hop, - &fl6->saddr); + proto = ipv6_push_nfrag_opts(skb, opt, proto, + &first_hop, + &fl6->saddr); } if (unlikely(seg_len > IPV6_MAXPLEN)) { @@ -1940,11 +1941,13 @@ struct sk_buff *__ip6_make_skb(struct sock *sk, __skb_pull(skb, skb_network_header_len(skb)); final_dst = &fl6->daddr; - if (opt && opt->opt_flen) - ipv6_push_frag_opts(skb, opt, &proto); - if (opt && opt->opt_nflen) - ipv6_push_nfrag_opts(skb, opt, &proto, &final_dst, &fl6->saddr); - + if (opt) { + if (opt->opt_flen) + proto = ipv6_push_frag_opts(skb, opt, proto); + if (opt->opt_nflen) + proto = ipv6_push_nfrag_opts(skb, opt, proto, + &final_dst, &fl6->saddr); + } skb_push(skb, sizeof(struct ipv6hdr)); skb_reset_network_header(skb); hdr = ipv6_hdr(skb); diff --git a/net/ipv6/ip6_tunnel.c b/net/ipv6/ip6_tunnel.c index f68f6f110a3e7..6fca0868b5a23 100644 --- a/net/ipv6/ip6_tunnel.c +++ b/net/ipv6/ip6_tunnel.c @@ -1265,7 +1265,7 @@ route_lookup: if (encap_limit >= 0) { init_tel_txopt(&opt, encap_limit); - ipv6_push_frag_opts(skb, &opt.ops, &proto); + proto = ipv6_push_frag_opts(skb, &opt.ops, proto); } skb_push(skb, sizeof(struct ipv6hdr)); -- 2.47.3