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[198.145.64.163]) by smtp.gmail.com with ESMTPSA id m6sm4511294pfc.151.2021.07.27.14.16.49 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 27 Jul 2021 14:16:50 -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 62/64] netlink: Avoid false-positive memcpy() warning Date: Tue, 27 Jul 2021 13:58:53 -0700 Message-Id: <20210727205855.411487-63-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=1678; h=from:subject; bh=vs/nNFIrJxwpI5nY+xgEPX6hqzmriBWLvM3b/eZbMbo=; b=owEBbQKS/ZANAwAKAYly9N/cbcAmAcsmYgBhAHOOsotWr+xLgDAagynSwACfihlJOnm7qN9/Mu92 bGzCtbGJAjMEAAEKAB0WIQSlw/aPIp3WD3I+bhOJcvTf3G3AJgUCYQBzjgAKCRCJcvTf3G3AJj/ZD/ 9ntjJhpq8fBwkjGH+dUg05xTxsNzIOuiH2+WA92AhYmbos7FaDGTm1g+GjbS9tYtH4WO2HSlLQe7LQ FBHmUbu6aiUm0Adb7gUZE3muL85N91x3mnnmxIoo2J/A/2tV0zkQyLUOckCj8VK+SR9BfW61OwCULU 7dXUvxZG2bCfldSz9FFpeTg6B3n38v7ZsFzE0Z+OKqNG5B6gy6nq9hQDiK5eWY7jsHwu6TaCX2KdWP ox3h/ObmvzejD4r5bqMjjhvU16eLjApW1M3mdaJGfxBeiC7Hn4U7R0R/a57zPmDRTbz/MhdWbOOFDp ABNXWuprZfW5V1fn74AOyo4Qdi0fWAhH4ttZZuPFnGp39cUNy/oe1zMgHhD+XjhBS0RMucpc7gNElk gk4SaMhbgnC4Ou6wBhA+yQfDvMUjqtRWUuRYmsFZ5Llmrlr/jWnsbjlt39vSdTBC9vTKSqnxgt1omQ fQi/9qcta+kyf71Lx1H+c1m8ve+vz4yBPxEJ5ztsLmSYk+J3LMojiNObOTsmlTFbCj4ZoDBFSpnQga mYRnTFbLCAQHQtPXM2pa7+qmWPgSz70szWlbF1IDWFBmyv8JppWdlZQu+0ThYGXTdnhi+QLNwm/WxH Zw293JAH5hVEyNiT/+/fkkV4VjclpW+bzGJvvMPBwvfpxzJKDGLjwSx2fyMw== X-Developer-Key: i=keescook@chromium.org; a=openpgp; fpr=A5C3F68F229DD60F723E6E138972F4DFDC6DC026 Precedence: bulk List-ID: X-Mailing-List: linux-kbuild@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. Add a flexible array member to mark the end of struct nlmsghdr, and split the memcpy() to avoid false positive memcpy() warning: memcpy: detected field-spanning write (size 32) of single field (size 16) Signed-off-by: Kees Cook --- include/uapi/linux/netlink.h | 1 + net/netlink/af_netlink.c | 4 +++- 2 files changed, 4 insertions(+), 1 deletion(-) diff --git a/include/uapi/linux/netlink.h b/include/uapi/linux/netlink.h index 4c0cde075c27..ddeaa748df5e 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 contents[]; }; /* Flags values */ diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c index 24b7cf447bc5..f2dd99e96822 100644 --- a/net/netlink/af_netlink.c +++ b/net/netlink/af_netlink.c @@ -2447,7 +2447,9 @@ 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)); + memcpy(&errmsg->msg, nlh, sizeof(*nlh)); + if (payload > sizeof(*errmsg)) + memcpy(errmsg->msg.contents, nlh->contents, nlh->nlmsg_len - sizeof(*nlh)); if (nlk_has_extack && extack) { if (extack->_msg) {