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[198.145.64.163]) by smtp.gmail.com with ESMTPSA id k1sm5323404pga.70.2021.07.27.14.36.49 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 27 Jul 2021 14:36:50 -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 59/64] fortify: Detect struct member overflows in memset() at compile-time Date: Tue, 27 Jul 2021 13:58:50 -0700 Message-Id: <20210727205855.411487-60-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=3639; h=from:subject; bh=8zP6zQoAqqqGG8HMfjFP4w1KGnbp2hqGXaP0Hbd76y4=; b=owEBbQKS/ZANAwAKAYly9N/cbcAmAcsmYgBhAHON3fO1CHh8uvdaQO6AN9FBZe6nYDGm5e9VLXU1 qyRUNQmJAjMEAAEKAB0WIQSlw/aPIp3WD3I+bhOJcvTf3G3AJgUCYQBzjQAKCRCJcvTf3G3AJqP1EA CVSH0wpqbxZ3IE5MoFsr86U7Yah0Hg+0c1Z0WseIk4zQvGBt5+jFc3XcFlXK0ePD9t1SEiUdtsmdTk f1ieawudX3fOXtTF+cENRebLnsBwHqJvcXhqWYybCiJZ5svrL/RhkKPjsZTl6p5Z09OONrfhkbCqOY ay2thxGsYWVYDMmGGQNm6DiY+eqdfIMpHIvddl9XbfH5zi6U1bthLezg2Y4qm0wOu/5ef45dfAvYyF oCnwD8HMnm/UEESuw5A1lfsDFrsjRjZvhke7e0iXTG1/CdsxQCbJdTGbmj/FbSwwxOIKvnAolZyJ1N Ytjm2RsjqaNYCBv3huLAScFJY0tonJLIjHFH/qNLF8HruT9cRTzhO1gRYqgMQ+klJaTJpljcvscTr/ V2vtj25ws/lTocXKXlKMHBDJvSYFfmuK5cOpt0DBPuNPdLyfE/QNCMFYDuE3D84/ghfuxMdMhh5IAD jcvjTg10ak7Kw9gd5dxLgqM3Jh3xlYuwUJ3NGRv3QnXsSMvCWQ4AA0SOp+ObPI+gAm9AdLedDedwyU jEhSXCZOIlnkATKds9+upOvmJWe7tDk7TJC9vK3pRhO7XoQV9FTH569mha1nU31WBCq88G6VlP5pfR MVMjAFcoVy2UbuarVe6jUsybzWsznx5I5wLnLraRpEfhYsvyhOtL0DVWQmVQ== X-Developer-Key: i=keescook@chromium.org; a=openpgp; fpr=A5C3F68F229DD60F723E6E138972F4DFDC6DC026 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-wireless@vger.kernel.org As done for memcpy(), also update memset() to use the same tightened compile-time bounds checking under CONFIG_FORTIFY_SOURCE. Signed-off-by: Kees Cook --- include/linux/fortify-string.h | 54 ++++++++++++++++--- .../write_overflow_field-memset.c | 5 ++ 2 files changed, 51 insertions(+), 8 deletions(-) create mode 100644 lib/test_fortify/write_overflow_field-memset.c diff --git a/include/linux/fortify-string.h b/include/linux/fortify-string.h index 2ffa5224aaac..718325331021 100644 --- a/include/linux/fortify-string.h +++ b/include/linux/fortify-string.h @@ -175,17 +175,56 @@ __FORTIFY_INLINE char *strncat(char *p, const char *q, __kernel_size_t count) return p; } -__FORTIFY_INLINE void *memset(void *p, int c, __kernel_size_t size) +__FORTIFY_INLINE void fortify_memset_chk(__kernel_size_t size, + const size_t p_size, + const size_t p_size_field) { - size_t p_size = __builtin_object_size(p, 0); + if (__builtin_constant_p(size)) { + /* + * Length argument is a constant expression, so we + * can perform compile-time bounds checking where + * buffer sizes are known. + */ - if (__builtin_constant_p(size) && p_size < size) - __write_overflow(); - if (p_size < size) - fortify_panic(__func__); - return __underlying_memset(p, c, size); + /* Error when size is larger than enclosing struct. */ + if (p_size > p_size_field && p_size < size) + __write_overflow(); + + /* Warn when write size is larger than dest field. */ + if (p_size_field < size) + __write_overflow_field(); + } + /* + * At this point, length argument may not be a constant expression, + * so run-time bounds checking can be done where buffer sizes are + * known. (This is not an "else" because the above checks may only + * be compile-time warnings, and we want to still warn for run-time + * overflows.) + */ + + /* + * Always stop accesses beyond the struct that contains the + * field, when the buffer's remaining size is known. + * (The -1 test is to optimize away checks where the buffer + * lengths are unknown.) + */ + if (p_size != (size_t)(-1) && p_size < size) + fortify_panic("memset"); } +#define __fortify_memset_chk(p, c, size, p_size, p_size_field) ({ \ + size_t __fortify_size = (size_t)(size); \ + fortify_memset_chk(__fortify_size, p_size, p_size_field), \ + __underlying_memset(p, c, __fortify_size); \ +}) + +/* + * __builtin_object_size() must be captured here to avoid evaluating argument + * side-effects further into the macro layers. + */ +#define memset(p, c, s) __fortify_memset_chk(p, c, s, \ + __builtin_object_size(p, 0), __builtin_object_size(p, 1)) + /* * To make sure the compiler can enforce protection against buffer overflows, * memcpy(), memmove(), and memset() must not be used beyond individual @@ -373,7 +412,6 @@ __FORTIFY_INLINE char *strcpy(char *p, const char *q) /* Don't use these outside the FORITFY_SOURCE implementation */ #undef __underlying_memchr #undef __underlying_memcmp -#undef __underlying_memset #undef __underlying_strcat #undef __underlying_strcpy #undef __underlying_strlen diff --git a/lib/test_fortify/write_overflow_field-memset.c b/lib/test_fortify/write_overflow_field-memset.c new file mode 100644 index 000000000000..2331da26909e --- /dev/null +++ b/lib/test_fortify/write_overflow_field-memset.c @@ -0,0 +1,5 @@ +// SPDX-License-Identifier: GPL-2.0-only +#define TEST \ + memset(instance.buf, 0x42, sizeof(instance.buf) + 1) + +#include "test_fortify.h" -- 2.30.2