From e584855b2289fd8155b837f00f67343cc9cd8f66 Mon Sep 17 00:00:00 2001 From: Martin Willers Date: Tue, 17 Nov 2020 01:27:36 +0100 Subject: Avoid memory access errors with 4-chars context ids (#250) For a 4-chars CTXID, i.e. one that does not include a null character, the strlen() calls were happily accessing memory until they eventually encountered a null character somewhere in memory. This was detected by valgrind, which reported a memory error when using a CTXID such as "INTM": ==21924== Conditional jump or move depends on uninitialised value(s) ==21924== at 0x4C30F78: strlen (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so) ==21924== by 0x4E4B5A0: dlt_print_id (dlt_common.c:303) ==21924== by 0x4E4CF47: dlt_message_header_flags (dlt_common.c:687) ==21924== by 0x4E51434: dlt_message_print_ascii (dlt_common.c:3169) ==21924== by 0x4E4247A: dlt_user_print_msg (dlt_user.c:4108) ==21924== by 0x4E46D92: dlt_user_log_send_log (dlt_user.c:3670) ==21924== by 0x4E46F14: dlt_user_log_write_finish (dlt_user.c:1611) Sanitize some code Using memset() and memcpy() is always preferable to hand-rolled loops, because compilers have built-in support for them. Signed-off-by: Martin Willers --- include/dlt/dlt_common.h | 17 +++++++++++++++++ src/shared/dlt_common.c | 23 +++++++++++++++-------- tests/gtest_dlt_common.cpp | 43 +++++++++++++++++++++++++++++++++++++++++++ 3 files changed, 75 insertions(+), 8 deletions(-) diff --git a/include/dlt/dlt_common.h b/include/dlt/dlt_common.h index 166395e..9bbd544 100644 --- a/include/dlt/dlt_common.h +++ b/include/dlt/dlt_common.h @@ -87,6 +87,12 @@ # include # endif +# if defined(__GNUC__) +# define PURE_FUNCTION __attribute__((pure)) +# else +# define PURE_FUNCTION /* nothing */ +# endif + # if !defined (__WIN32__) && !defined(_MSC_VER) # include # endif @@ -860,6 +866,17 @@ DltReturnValue dlt_print_mixed_string(char *text, int textlength, uint8_t *ptr, */ DltReturnValue dlt_print_char_string(char **text, int textlength, uint8_t *ptr, int size); +/** + * Helper function to determine a bounded length of a string. + * This function returns zero if @a str is a null pointer, + * and it returns @a maxsize if the null character was not found in the first @a maxsize bytes of @a str. + * This is a re-implementation of C11's strnlen_s, which we cannot yet assume to be available. + * @param text pointer to string whose length is to be determined + * @param maxsize maximal considered length of @a str + * @return the bounded length of the string + */ +PURE_FUNCTION size_t dlt_strnlen_s(const char* str, size_t maxsize); + /** * Helper function to print an id. * @param text pointer to ASCII string where to write the id diff --git a/src/shared/dlt_common.c b/src/shared/dlt_common.c index 2ff3775..254f4ce 100644 --- a/src/shared/dlt_common.c +++ b/src/shared/dlt_common.c @@ -286,25 +286,32 @@ DltReturnValue dlt_print_char_string(char **text, int textlength, uint8_t *ptr, return DLT_RETURN_OK; } +size_t dlt_strnlen_s(const char* str, size_t maxsize) +{ + if (str == NULL) + return 0; + + for (size_t i = 0; i < maxsize; ++i) { + if (str[i] == '\0') + return i; + } + return maxsize; +} + void dlt_print_id(char *text, const char *id) { /* check nullpointer */ if ((text == NULL) || (id == NULL)) return; - int i, len; - /* Initialize text */ - for (i = 0; i < DLT_ID_SIZE; i++) - text[i] = '-'; + memset(text, '-', DLT_ID_SIZE); text[DLT_ID_SIZE] = 0; - len = ((strlen(id) <= DLT_ID_SIZE) ? strlen(id) : DLT_ID_SIZE); + size_t len = dlt_strnlen_s(id, DLT_ID_SIZE); - /* Check id*/ - for (i = 0; i < len; i++) - text[i] = id[i]; + memcpy(text, id, len); } void dlt_set_id(char *id, const char *text) diff --git a/tests/gtest_dlt_common.cpp b/tests/gtest_dlt_common.cpp index adbc87d..9afb830 100644 --- a/tests/gtest_dlt_common.cpp +++ b/tests/gtest_dlt_common.cpp @@ -4067,6 +4067,49 @@ TEST(t_dlt_print_char_string, nullpointer) +/* Begin Method:dlt_common::dlt_strnlen_s*/ +TEST(t_dlt_strnlen_s, nullpointer) +{ + size_t len = dlt_strnlen_s(NULL, 0); + EXPECT_EQ(len, 0); +} + +TEST(t_dlt_strnlen_s, len_zero) +{ + const char text[] = "The Quick Brown Fox"; + + size_t len = dlt_strnlen_s(text, 0); + EXPECT_EQ(len, 0); +} + +TEST(t_dlt_strnlen_s, len_smaller) +{ + const char text[] = "The Quick Brown Fox"; + + size_t len = dlt_strnlen_s(text, 10); + EXPECT_EQ(len, 10); +} + +TEST(t_dlt_strnlen_s, len_equal) +{ + const char text[] = "The Quick Brown Fox"; + + size_t len = dlt_strnlen_s(text, 19); + EXPECT_EQ(len, 19); +} + +TEST(t_dlt_strnlen_s, len_larger) +{ + const char text[] = "The Quick Brown Fox"; + + size_t len = dlt_strnlen_s(text, 100); + EXPECT_EQ(len, 19); +} +/* End Method:dlt_common::dlt_strnlen_s*/ + + + + /* Begin Method:dlt_common::dlt_print_id */ TEST(t_dlt_print_id, normal) { -- cgit v1.2.1