From 4ffe2b24f5c7a856e607370e1e559e4c94803809 Mon Sep 17 00:00:00 2001 From: cgyurgyik Date: Tue, 23 Jun 2020 07:19:45 -0400 Subject: [PATCH] [libc] Add fuzz test for strcmp. Summary: Adds a fuzz test for string comparison. This takes in two strings with associated lengths. Verifies each string contains at least one character, and that the last character is the null terminator. Then, finds the first instance where one of the following does not hold: 1. i < min(size1, size2) 2. s1[i] == s2[i] 3. s1[i] != '\0' The result of strcmp is then compared to the value of the difference between s1[i] and s2[i]. For thoroughness, the operands are reversed and also checked. Reviewers: sivachandra, PaulkaToast Reviewed By: sivachandra, PaulkaToast Subscribers: mgorny, tschuett, ecnelises, libc-commits Tags: #libc-project Differential Revision: https://reviews.llvm.org/D82247 --- libc/fuzzing/string/strcmp_fuzz.cpp | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-) diff --git a/libc/fuzzing/string/strcmp_fuzz.cpp b/libc/fuzzing/string/strcmp_fuzz.cpp index 14c6e4d10e71..6ba8440642ce 100644 --- a/libc/fuzzing/string/strcmp_fuzz.cpp +++ b/libc/fuzzing/string/strcmp_fuzz.cpp @@ -10,7 +10,6 @@ /// //===----------------------------------------------------------------------===// #include "src/string/strcmp.h" -#include #include extern "C" int LLVMFuzzerTestTwoInputs(const uint8_t *data1, size_t size1, @@ -25,15 +24,17 @@ extern "C" int LLVMFuzzerTestTwoInputs(const uint8_t *data1, size_t size1, const char *s1 = reinterpret_cast(data1); const char *s2 = reinterpret_cast(data2); - const size_t minimum_size = std::min(size1, size2); + const size_t minimum_size = size1 < size2 ? size1 : size2; // Iterate through until either the minimum size is hit, // a character is the null terminator, or the first set // of differed bytes between s1 and s2 are found. // No bytes following a null byte should be compared. size_t i; - for (i = 0; i < minimum_size && s1[i] && s1[i] == s2[i]; ++i) - ; + for (i = 0; i < minimum_size; ++i) { + if (!s1[i] || s1[i] != s2[i]) + break; + } int expected_result = s1[i] - s2[i]; int actual_result = __llvm_libc::strcmp(s1, s2);