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[198.0.35.241]) by smtp.gmail.com with ESMTPSA id e19-20020a62aa13000000b005b6f63c6cf4sm217194pff.30.2023.03.02.14.49.52 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 02 Mar 2023 14:49:52 -0800 (PST) From: Kees Cook To: Joel Fernandes Cc: Kees Cook , Jakub Kicinski , stable@vger.kernel.org, Masahiro Yamada , Greg Kroah-Hartman , linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org Subject: [PATCH] kheaders: Use array declaration instead of char Date: Thu, 2 Mar 2023 14:49:50 -0800 Message-Id: <20230302224946.never.243-kees@kernel.org> X-Mailer: git-send-email 2.34.1 MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=2075; h=from:subject:message-id; bh=eLj/PflKjatP3hFY0i0HHeuMwWpjFzg2cBxv81U9QkM=; b=owEBbQKS/ZANAwAKAYly9N/cbcAmAcsmYgBkASgOFlZ1ftATS5I9PtciOtLxZpppkpTfsbekhvi0 AiYPKIuJAjMEAAEKAB0WIQSlw/aPIp3WD3I+bhOJcvTf3G3AJgUCZAEoDgAKCRCJcvTf3G3AJkeqD/ 0UKRxmCYQN06lvmilRYvIyKjBpP1mKZf3n4bjCclIFAOJ/ZLkeIiUPLMpOo34kP1jZOaaJapJsc3th WwaEdtGNaVCu8UyDipj4c1YBMdSYL1xekEJtkPnelZnDwEutxQNxEy38mpAgoCb541wlTw9w0YbPAi yyJa+NJI5l/x2IxhPwKD3F19cxe9JlWTBqC82IpvTUY7l9jxv1XcnM4ZJA0D5mlyDzOovN10GhQdVj aEPKTTjm8ifvUsuiODnrsguQPwwvoadopjqjwgGLlmxM9G6IfAD8F1zIWFo6XFsPfrxhRaQvO/bjcm GLXRBa3GPb0I05K21/lSkajRvk5xOfs+FSpF9S+PztoqgHOnI4wDRrL6zhdp7JzxZQ6IzVsukq1Xqe UUuvWc4OfJN2Q8j3Jkb4aq3NPpQPMnvOip9hlQdEpgRR4foO95+kX2XpQ3nK1uODIiDxCb3y+ScURs iI+/TAUPcYLIV6i59xNWz9yNv2kfisiAXVg5AQdf9jcJbJn6LhGEaW0GlpQc6ocYRRliSxzE91OD9l UKkvUONcTKTMx7q7/bUY+E+2qmFHnoN1HUb//TPtpO1Km4DypVSVz7flMS9OWbF8y6sX/eP2Bk1ceM c8dEuWg6AeUgSV0SwOuqvYletGKA8FxVGpvNRif+xcgiCXHeBQE6QmbVeyjw== X-Developer-Key: i=keescook@chromium.org; a=openpgp; fpr=A5C3F68F229DD60F723E6E138972F4DFDC6DC026 Precedence: bulk List-ID: X-Mailing-List: linux-hardening@vger.kernel.org Under CONFIG_FORTIFY_SOURCE, memcpy() will check the size of destination and source buffers. Defining kernel_headers_data as "char" would trip this check. Since these addresses are treated as byte arrays, define them as arrays (as done everywhere else). This was seen with: $ cat /sys/kernel/kheaders.tar.xz >> /dev/null detected buffer overflow in memcpy kernel BUG at lib/string_helpers.c:1027! ... RIP: 0010:fortify_panic+0xf/0x20 [...] Call Trace: ikheaders_read+0x45/0x50 [kheaders] kernfs_fop_read_iter+0x1a4/0x2f0 ... Reported-by: Jakub Kicinski Link: https://lore.kernel.org/bpf/20230302112130.6e402a98@kernel.org/ Tested-by: Jakub Kicinski Fixes: 43d8ce9d65a5 ("Provide in-kernel headers to make extending kernel easier") Cc: Joel Fernandes (Google) Cc: stable@vger.kernel.org Signed-off-by: Kees Cook Acked-by: Joel Fernandes (Google) Reviewed-by: Alexander Lobakin --- kernel/kheaders.c | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-) diff --git a/kernel/kheaders.c b/kernel/kheaders.c index 8f69772af77b..42163c9e94e5 100644 --- a/kernel/kheaders.c +++ b/kernel/kheaders.c @@ -26,15 +26,15 @@ asm ( " .popsection \n" ); -extern char kernel_headers_data; -extern char kernel_headers_data_end; +extern char kernel_headers_data[]; +extern char kernel_headers_data_end[]; static ssize_t ikheaders_read(struct file *file, struct kobject *kobj, struct bin_attribute *bin_attr, char *buf, loff_t off, size_t len) { - memcpy(buf, &kernel_headers_data + off, len); + memcpy(buf, &kernel_headers_data[off], len); return len; } @@ -48,8 +48,8 @@ static struct bin_attribute kheaders_attr __ro_after_init = { static int __init ikheaders_init(void) { - kheaders_attr.size = (&kernel_headers_data_end - - &kernel_headers_data); + kheaders_attr.size = (kernel_headers_data_end - + kernel_headers_data); return sysfs_create_bin_file(kernel_kobj, &kheaders_attr); }