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[198.145.64.163]) by smtp.gmail.com with ESMTPSA id s5sm5498942pgp.81.2021.08.17.23.06.02 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 17 Aug 2021 23:06:05 -0700 (PDT) From: Kees Cook To: linux-kernel@vger.kernel.org Cc: Kees Cook , "Gustavo A. R. Silva" , Greg Kroah-Hartman , Andrew Morton , 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, Rasmus Villemoes , linux-hardening@vger.kernel.org Subject: [PATCH v2 62/63] fortify: Detect struct member overflows in memset() at compile-time Date: Tue, 17 Aug 2021 23:05:32 -0700 Message-Id: <20210818060533.3569517-63-keescook@chromium.org> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20210818060533.3569517-1-keescook@chromium.org> References: <20210818060533.3569517-1-keescook@chromium.org> MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=3657; h=from:subject; bh=x4SNp17MkJsMDii5dKL06SU0zDLItyjvjIE8yvAGOLw=; b=owEBbQKS/ZANAwAKAYly9N/cbcAmAcsmYgBhHKMsuEVllcthHvVoZOOtiNzdZSQL+MVxm5lZYC08 cYuVeeiJAjMEAAEKAB0WIQSlw/aPIp3WD3I+bhOJcvTf3G3AJgUCYRyjLAAKCRCJcvTf3G3AJhFJD/ 0YywcHnMj1c/NexxJTDTdAYqmtmTUD8x82Ns/wjrQAyODC3hv/6fd7/lXy7KLnBf3O7mSQRPo1siWq mi4sD6BTm3hIo3GuFOJ8CTfGgnxxwdN6j/TkfuxlpJSHWlG8CdQJaYNCYJgI7QT0k7mcvIcU0Yiu5/ YaVOOC0zQ85PA//3PbzguuPv50kBbxQ5bQSD5XS5ptljehOSJcCJ66K/cFUtnJoZrfF5m7naOzclM+ YSn8wlMr9aQqL6DEc6etgSVI2n22I9gcsWaObJAPYCut15PH0LnKu3TXUtF2oQy91xDTCZ0kCAuzqt 5poO59eUPNtjb6apuyTyI2sng4UXAVOqnFeKce+zQIoGAdIb5GjE13ffC5AAon3CmAbxRE5FUufUrx zUIYqjgohnwHn6YDtth4aIZB/W2kLG2W2q4TWuZjMxEaw0SVrnd4P2jJSHU8B8d1a6PkAs8epAq0gc D69QvVpSd/j5KuzMZUdDpOKxgIKUXFGXliJiDsu+4vuCdioBLapgoOTvVDBi1LirQl6lP45HoxFQ0b S64cenON/jFuSH9ZmumaJj1QScmPVkoNRRs09YB5f0juMR7C0bopH+EEmaqk++upwBm1nP/e/Dtxew r7vE625A/r6FGg4xIb9flyd3LdIf3HsRkH/Bt6+5XCnDvRxE/u5ev7V+yD8w== X-Developer-Key: i=keescook@chromium.org; a=openpgp; fpr=A5C3F68F229DD60F723E6E138972F4DFDC6DC026 Precedence: bulk List-ID: X-Mailing-List: netdev@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 0120d463ba33..7de4673dfe2c 100644 --- a/include/linux/fortify-string.h +++ b/include/linux/fortify-string.h @@ -198,17 +198,56 @@ __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(p_size_field, size); + } + /* + * 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 @@ -399,7 +438,6 @@ __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"