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[198.145.64.163]) by smtp.gmail.com with ESMTPSA id y23sm4655958pgf.38.2021.07.27.14.06.50 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 27 Jul 2021 14:06:50 -0700 (PDT) From: Kees Cook To: linux-hardening@vger.kernel.org Cc: Kees Cook , "Gustavo A. R. Silva" , Keith Packard , Greg Kroah-Hartman , Andrew Morton , linux-kernel@vger.kernel.org, linux-wireless@vger.kernel.org, netdev@vger.kernel.org, dri-devel@lists.freedesktop.org, linux-staging@lists.linux.dev, linux-block@vger.kernel.org, linux-kbuild@vger.kernel.org, clang-built-linux@googlegroups.com Subject: [PATCH 19/64] ip: Use struct_group() for memcpy() regions Date: Tue, 27 Jul 2021 13:58:10 -0700 Message-Id: <20210727205855.411487-20-keescook@chromium.org> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20210727205855.411487-1-keescook@chromium.org> References: <20210727205855.411487-1-keescook@chromium.org> MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=5544; h=from:subject; bh=EW2OlP80ZbFYA2et85VLFWinFxHDZ/JfYcx96uwve2A=; b=owEBbQKS/ZANAwAKAYly9N/cbcAmAcsmYgBhAHOE1QionXEAsnSiPxVw5wfkIt8+He7UKLQGrMmI c3kN8gqJAjMEAAEKAB0WIQSlw/aPIp3WD3I+bhOJcvTf3G3AJgUCYQBzhAAKCRCJcvTf3G3AJgwWD/ sH6JiJOlqMdZB/DaJUVswYUCsszxQOHKvFJps95qmqpJBMRDsH2lLBKm2a6gmCHlmLHrpZE35CObwM nj+RWt9ixoNH4L81O+98xW2w1VPy57Ri6Pf6Yvn44gHEPmKAxV7pdf/rNyEVZZ+t4EbwjFrLIOF9Cu cXpnowGMFNqPdKCrUf/0aeZoSOJ/IGRJtmxUClP9U/1zfg/R1in74Yi149wzVruBUBUSTvsQc4SA0s QQYq5W7ixXMQ8l0YTWGa8ymTzcKK7P60aP4vm7HBJJCHyQR/BwdRDvijeZ1qYLlddgvFs0UULN0oQe vVd8qbWGt4gKDPylfKfgz6uaNSz+jJ43ZF5fCDL1Jt0BrSc+Cx63VBDSBSytHoarJkaqTtC3GRNWES xTVy3dTnpag/Lj92bhpS2+EWrLsiDNWEeuOb1Er5+25XBNHz+Y8frHGoRemgsL3Qs1EVYOTdxlFHG3 V6rjjqoRPfWMWpN0e7jogaTYc3cRUXBSen9HIsPGXHu3xrGH+bvNJ3uQ1VOdugyYnP+7PFkJ7FwuPS RBc5nf5hj3ojUnMeyIYKt1IK14Do/EQKUtgRpkmkN7YhsN1/yquUdxgGZ8x/Zi1LZI/UZ6FLaxcXVK Fc7a3ewBBcn4SXZY0R5FI5JHXF0Ahz8hNwHzp01WiTwpznvQKOKE/eRBuuoQ== X-Developer-Key: i=keescook@chromium.org; a=openpgp; fpr=A5C3F68F229DD60F723E6E138972F4DFDC6DC026 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-hardening@vger.kernel.org In preparation for FORTIFY_SOURCE performing compile-time and run-time field bounds checking for memcpy(), memmove(), and memset(), avoid intentionally writing across neighboring fields. Use struct_group() in struct flowi4, struct ipv4hdr, and struct ipv6hdr around members saddr and daddr, so they can be referenced together. This will allow memcpy() and sizeof() to more easily reason about sizes, improve readability, and avoid future warnings about writing beyond the end of saddr. "pahole" shows no size nor member offset changes to struct flowi4. "objdump -d" shows no meaningful object code changes (i.e. only source line number induced differences.) Note that since this is a UAPI header, struct_group() has been open coded. Signed-off-by: Kees Cook --- include/net/flow.h | 6 ++++-- include/uapi/linux/if_ether.h | 12 ++++++++++-- include/uapi/linux/ip.h | 12 ++++++++++-- include/uapi/linux/ipv6.h | 12 ++++++++++-- net/core/flow_dissector.c | 10 ++++++---- net/ipv4/ip_output.c | 6 ++---- 6 files changed, 42 insertions(+), 16 deletions(-) diff --git a/include/net/flow.h b/include/net/flow.h index 6f5e70240071..f1a3b6c8eae2 100644 --- a/include/net/flow.h +++ b/include/net/flow.h @@ -81,8 +81,10 @@ struct flowi4 { #define flowi4_multipath_hash __fl_common.flowic_multipath_hash /* (saddr,daddr) must be grouped, same order as in IP header */ - __be32 saddr; - __be32 daddr; + struct_group(addrs, + __be32 saddr; + __be32 daddr; + ); union flowi_uli uli; #define fl4_sport uli.ports.sport diff --git a/include/uapi/linux/if_ether.h b/include/uapi/linux/if_ether.h index a0b637911d3c..8f5667b2ea92 100644 --- a/include/uapi/linux/if_ether.h +++ b/include/uapi/linux/if_ether.h @@ -163,8 +163,16 @@ #if __UAPI_DEF_ETHHDR struct ethhdr { - unsigned char h_dest[ETH_ALEN]; /* destination eth addr */ - unsigned char h_source[ETH_ALEN]; /* source ether addr */ + union { + struct { + unsigned char h_dest[ETH_ALEN]; /* destination eth addr */ + unsigned char h_source[ETH_ALEN]; /* source ether addr */ + }; + struct { + unsigned char h_dest[ETH_ALEN]; /* destination eth addr */ + unsigned char h_source[ETH_ALEN]; /* source ether addr */ + } addrs; + }; __be16 h_proto; /* packet type ID field */ } __attribute__((packed)); #endif diff --git a/include/uapi/linux/ip.h b/include/uapi/linux/ip.h index e42d13b55cf3..33647a37e56b 100644 --- a/include/uapi/linux/ip.h +++ b/include/uapi/linux/ip.h @@ -100,8 +100,16 @@ struct iphdr { __u8 ttl; __u8 protocol; __sum16 check; - __be32 saddr; - __be32 daddr; + union { + struct { + __be32 saddr; + __be32 daddr; + } addrs; + struct { + __be32 saddr; + __be32 daddr; + }; + }; /*The options start here. */ }; diff --git a/include/uapi/linux/ipv6.h b/include/uapi/linux/ipv6.h index b243a53fa985..1c26d32e733b 100644 --- a/include/uapi/linux/ipv6.h +++ b/include/uapi/linux/ipv6.h @@ -130,8 +130,16 @@ struct ipv6hdr { __u8 nexthdr; __u8 hop_limit; - struct in6_addr saddr; - struct in6_addr daddr; + union { + struct { + struct in6_addr saddr; + struct in6_addr daddr; + } addrs; + struct { + struct in6_addr saddr; + struct in6_addr daddr; + }; + }; }; diff --git a/net/core/flow_dissector.c b/net/core/flow_dissector.c index 2aadbfc5193b..87655a2ac200 100644 --- a/net/core/flow_dissector.c +++ b/net/core/flow_dissector.c @@ -1029,7 +1029,8 @@ bool __skb_flow_dissect(const struct net *net, key_eth_addrs = skb_flow_dissector_target(flow_dissector, FLOW_DISSECTOR_KEY_ETH_ADDRS, target_container); - memcpy(key_eth_addrs, ð->h_dest, sizeof(*key_eth_addrs)); + BUILD_BUG_ON(sizeof(*key_eth_addrs) != sizeof(eth->addrs)); + memcpy(key_eth_addrs, ð->addrs, sizeof(*key_eth_addrs)); } proto_again: @@ -1056,8 +1057,8 @@ bool __skb_flow_dissect(const struct net *net, FLOW_DISSECTOR_KEY_IPV4_ADDRS, target_container); - memcpy(&key_addrs->v4addrs, &iph->saddr, - sizeof(key_addrs->v4addrs)); + BUILD_BUG_ON(sizeof(key_addrs->v4addrs) != sizeof(iph->addrs)); + memcpy(&key_addrs->v4addrs, &iph->addrs, sizeof(iph->addrs)); key_control->addr_type = FLOW_DISSECTOR_KEY_IPV4_ADDRS; } @@ -1101,7 +1102,8 @@ bool __skb_flow_dissect(const struct net *net, FLOW_DISSECTOR_KEY_IPV6_ADDRS, target_container); - memcpy(&key_addrs->v6addrs, &iph->saddr, + BUILD_BUG_ON(sizeof(iph->addrs) != sizeof(key_addrs->v6addrs)); + memcpy(&key_addrs->v6addrs, &iph->addrs, sizeof(key_addrs->v6addrs)); key_control->addr_type = FLOW_DISSECTOR_KEY_IPV6_ADDRS; } diff --git a/net/ipv4/ip_output.c b/net/ipv4/ip_output.c index 8d8a8da3ae7e..58603995d889 100644 --- a/net/ipv4/ip_output.c +++ b/net/ipv4/ip_output.c @@ -444,10 +444,8 @@ EXPORT_SYMBOL(ip_output); */ static void ip_copy_addrs(struct iphdr *iph, const struct flowi4 *fl4) { - BUILD_BUG_ON(offsetof(typeof(*fl4), daddr) != - offsetof(typeof(*fl4), saddr) + sizeof(fl4->saddr)); - memcpy(&iph->saddr, &fl4->saddr, - sizeof(fl4->saddr) + sizeof(fl4->daddr)); + BUILD_BUG_ON(sizeof(iph->addrs) != sizeof(fl4->addrs)); + memcpy(&iph->addrs, &fl4->addrs, sizeof(fl4->addrs)); } /* Note: skb->sk can be different from sk, in case of tunnels */ -- 2.30.2