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[198.145.64.163]) by smtp.gmail.com with ESMTPSA id k8-20020a170902ce0800b0015e8d4eb283sm7000015plg.205.2022.05.03.18.47.33 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 03 May 2022 18:47:33 -0700 (PDT) From: Kees Cook To: "Gustavo A . R . Silva" Cc: Kees Cook , Rasmus Villemoes , "David S. Miller" , Jakub Kicinski , Rich Felker , Eric Dumazet , netdev@vger.kernel.org, Alexei Starovoitov , alsa-devel@alsa-project.org, Al Viro , Andrew Gabbasov , Andrew Morton , Andy Gross , Andy Lavr , Arend van Spriel , Baowen Zheng , Bjorn Andersson , Boris Ostrovsky , Bradley Grove , brcm80211-dev-list.pdl@broadcom.com, Christian Brauner , =?utf-8?q?Christian_G=C3=B6ttsche?= , Christian Lamparter , Chris Zankel , Cong Wang , Daniel Axtens , Daniel Vetter , Dan Williams , David Gow , David Howells , Dennis Dalessandro , devicetree@vger.kernel.org, Dexuan Cui , Dmitry Kasatkin , Eli Cohen , Eric Paris , Eugeniu Rosca , Felipe Balbi , Francis Laniel , Frank Rowand , Franky Lin , Greg Kroah-Hartman , Gregory Greenman , Guenter Roeck , Haiyang Zhang , Hante Meuleman , Herbert Xu , Hulk Robot , "James E.J. Bottomley" , James Morris , Jarkko Sakkinen , Jaroslav Kysela , Jason Gunthorpe , Jens Axboe , Johan Hedberg , Johannes Berg , Johannes Berg , John Keeping , Juergen Gross , Kalle Valo , Keith Packard , keyrings@vger.kernel.org, kunit-dev@googlegroups.com, Kuniyuki Iwashima , "K. Y. Srinivasan" , Lars-Peter Clausen , Lee Jones , Leon Romanovsky , Liam Girdwood , linux1394-devel@lists.sourceforge.net, linux-afs@lists.infradead.org, linux-arm-kernel@lists.infradead.org, linux-arm-msm@vger.kernel.org, linux-bluetooth@vger.kernel.org, linux-hardening@vger.kernel.org, linux-hyperv@vger.kernel.org, linux-integrity@vger.kernel.org, linux-rdma@vger.kernel.org, linux-scsi@vger.kernel.org, linux-security-module@vger.kernel.org, linux-usb@vger.kernel.org, linux-wireless@vger.kernel.org, linux-xtensa@linux-xtensa.org, llvm@lists.linux.dev, Loic Poulain , Louis Peens , Luca Coelho , Luiz Augusto von Dentz , Marc Dionne , Marcel Holtmann , Mark Brown , "Martin K. Petersen" , Max Filippov , Mimi Zohar , Muchun Song , Nathan Chancellor , Nick Desaulniers , =?utf-8?q?Nuno_S=C3=A1?= , Paolo Abeni , Paul Moore , Rob Herring , Russell King , selinux@vger.kernel.org, "Serge E. Hallyn" , SHA-cyfmac-dev-list@infineon.com, Simon Horman , Stefano Stabellini , Stefan Richter , Steffen Klassert , Stephen Hemminger , Stephen Smalley , Tadeusz Struk , Takashi Iwai , Tom Rix , Udipto Goswami , Vincenzo Frascino , wcn36xx@lists.infradead.org, Wei Liu , xen-devel@lists.xenproject.org, Xiu Jianfeng , Yang Yingliang Subject: [PATCH 01/32] netlink: Avoid memcpy() across flexible array boundary Date: Tue, 3 May 2022 18:44:10 -0700 Message-Id: <20220504014440.3697851-2-keescook@chromium.org> X-Mailer: git-send-email 2.32.0 In-Reply-To: <20220504014440.3697851-1-keescook@chromium.org> References: <20220504014440.3697851-1-keescook@chromium.org> MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=2198; h=from:subject; bh=m3+rrHA3rlt0sA4WgKzRJNTXeSTN4vWW0f0prUvbWYY=; b=owEBbQKS/ZANAwAKAYly9N/cbcAmAcsmYgBicdqAKYSI60YG7oB43Zm2qf2XEYFq9+0dv6JxgKQA Vag6ObOJAjMEAAEKAB0WIQSlw/aPIp3WD3I+bhOJcvTf3G3AJgUCYnHagAAKCRCJcvTf3G3AJt+PD/ 4wYVpcKl2liC+Uc4jUmmdOovQey8J6/k2HmeHGxkjjuXUGIWCxvRqFTmpp0zt8q6NeCY1dzyQE7A9N PW2CVLlv5GLZfLyBlcsOWL4hofk/Ed905HvAky/Dx8yVe0LszOaIIrWGUii70nX0RIZBcDlNYaOY4k wGJaGLJ9XI5Abp/vMi8qzgEIVt5Qty6Z+cfnpAvETE9FFC0ibHAuxSsOCPhKMgvWgkyDjMAVgJQC6t TKGjSE1Rwow+68x8cxXa3ZsNgWXO0wHDaWWB4/QUxyVrq/AqCxOvgu3SljXBgVpaeUF41w+gB7rTXz Jpn7XXtJZLIDQT9yoNDAsj8yjQSIPdaKabA732knKP+dXXvoimMLj17LWxunuIrNQJ5Awl5Dz2jNa4 96eQ4Eabc5miPNc5+9VOK1Wc20FUE/uqW/VkQkBWzcnLXslpLRuJ2jNTFzk50BKZOJ20vutotuSmWf 5gqjyHzRfK+iajoBCEV6nUiWN7ewO8XDDayLZtzu5foCWXgFFwp2ZWksNnvY6M1djooGD0fU2cMDkZ HK9WR0ZfO5zv8cE5RCjDXb25deVhtGS6HRKU3vBlDmFx3drFqOEK/4zwTej6ttVyJqAspxBqEq7xpi JDgQOkTfh60YdtsNYhykruXCL3NnFuRLtxOeMGWD4IL6YtPwYfH3V6aFCljQ== X-Developer-Key: i=keescook@chromium.org; a=openpgp; fpr=A5C3F68F229DD60F723E6E138972F4DFDC6DC026 Precedence: bulk List-ID: X-Mailing-List: linux-hardening@vger.kernel.org In preparation for run-time memcpy() bounds checking, split the nlmsg copying for error messages (which crosses a previous unspecified flexible array boundary) in half. Avoids the future run-time warning: memcpy: detected field-spanning write (size 32) of single field "&errmsg->msg" (size 16) Creates an explicit flexible array at the end of nlmsghdr for the payload, named "nlmsg_payload". There is no impact on UAPI; the sizeof(struct nlmsghdr) does not change, but now the compiler can better reason about where things are being copied. Fixed-by: Rasmus Villemoes Link: https://lore.kernel.org/lkml/d7251d92-150b-5346-6237-52afc154bb00@rasmusvillemoes.dk Cc: "David S. Miller" Cc: Jakub Kicinski Cc: Rich Felker Cc: Eric Dumazet Cc: netdev@vger.kernel.org Signed-off-by: Kees Cook --- include/uapi/linux/netlink.h | 1 + net/netlink/af_netlink.c | 5 ++++- 2 files changed, 5 insertions(+), 1 deletion(-) diff --git a/include/uapi/linux/netlink.h b/include/uapi/linux/netlink.h index 855dffb4c1c3..47f9342d51bc 100644 --- a/include/uapi/linux/netlink.h +++ b/include/uapi/linux/netlink.h @@ -47,6 +47,7 @@ struct nlmsghdr { __u16 nlmsg_flags; /* Additional flags */ __u32 nlmsg_seq; /* Sequence number */ __u32 nlmsg_pid; /* Sending process port ID */ + __u8 nlmsg_payload[];/* Contents of message */ }; /* Flags values */ diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c index 1b5a9c2e1c29..09346aee1022 100644 --- a/net/netlink/af_netlink.c +++ b/net/netlink/af_netlink.c @@ -2445,7 +2445,10 @@ void netlink_ack(struct sk_buff *in_skb, struct nlmsghdr *nlh, int err, NLMSG_ERROR, payload, flags); errmsg = nlmsg_data(rep); errmsg->error = err; - memcpy(&errmsg->msg, nlh, payload > sizeof(*errmsg) ? nlh->nlmsg_len : sizeof(*nlh)); + errmsg->msg = *nlh; + if (payload > sizeof(*errmsg)) + memcpy(errmsg->msg.nlmsg_payload, nlh->nlmsg_payload, + nlh->nlmsg_len - sizeof(*nlh)); if (nlk_has_extack && extack) { if (extack->_msg) {