WSL Ubuntu 22.04下使用zip.h库触发MemorySanitizer未初始化内存告警

我写了一段C语言代码用来打开加密Zip文件并读取内容，程序运行正常，但用Google MemorySanitizer（Msan）检测时，出现未初始化内存的告警；Valgrind和其他Google sanitizer工具都没报问题。当前环境是最新版WSL Ubuntu 22.04.2，所有包都是最新的。这个问题在另一台WSL Ubuntu 22.04机器上能复现，但WSL Ubuntu 20.04下没有告警。想问这段代码有没有疏漏？这个告警是库的bug还是Msan的误报？

错误栈信息 #

Uninitialized bytes in __interceptor_fopen64 at offset 0 inside [0x702000006ba0, 25)
==4630==WARNING: MemorySanitizer: use-of-uninitialized-value
    #0 0x7f944a1ed197 in BIO_new_file (/lib/x86_64-linux-gnu/libcrypto.so.3+0xe2197) (BuildId: f41db69553ac874b43c3ab46a4e0973d2405a1d1)
    #1 0x7f944a2243ed  (/lib/x86_64-linux-gnu/libcrypto.so.3+0x1193ed) (BuildId: f41db69553ac874b43c3ab46a4e0973d2405a1d1)
    #2 0x7f944a225051 in CONF_modules_load_file_ex (/lib/x86_64-linux-gnu/libcrypto.so.3+0x11a051) (BuildId: f41db69553ac874b43c3ab46a4e0973d2405a1d1)
    #3 0x7f944a2c9d2f  (/lib/x86_64-linux-gnu/libcrypto.so.3+0x1bed2f) (BuildId: f41db69553ac874b43c3ab46a4e0973d2405a1d1)
    #4 0x7f944a5faf67 in __pthread_once_slow nptl/./nptl/pthread_once.c:116:7
    #5 0x7f944a2cd76c in CRYPTO_THREAD_run_once (/lib/x86_64-linux-gnu/libcrypto.so.3+0x1c276c) (BuildId: f41db69553ac874b43c3ab46a4e0973d2405a1d1)
    #6 0x7f944a2ca795 in OPENSSL_init_crypto (/lib/x86_64-linux-gnu/libcrypto.so.3+0x1bf795) (BuildId: f41db69553ac874b43c3ab46a4e0973d2405a1d1)
    #7 0x7f944a2f3b1d  (/lib/x86_64-linux-gnu/libcrypto.so.3+0x1e8b1d) (BuildId: f41db69553ac874b43c3ab46a4e0973d2405a1d1)
    #8 0x7f944a2976de  (/lib/x86_64-linux-gnu/libcrypto.so.3+0x18c6de) (BuildId: f41db69553ac874b43c3ab46a4e0973d2405a1d1)
    #9 0x7f944a39f927  (/lib/x86_64-linux-gnu/libcrypto.so.3+0x294927) (BuildId: f41db69553ac874b43c3ab46a4e0973d2405a1d1)
    #10 0x7f944a3a007d  (/lib/x86_64-linux-gnu/libcrypto.so.3+0x29507d) (BuildId: f41db69553ac874b43c3ab46a4e0973d2405a1d1)
    #11 0x7f944a28b4b2 in EVP_MD_fetch (/lib/x86_64-linux-gnu/libcrypto.so.3+0x1804b2) (BuildId: f41db69553ac874b43c3ab46a4e0973d2405a1d1)
    #12 0x7f944a2ac9e5 in PKCS5_PBKDF2_HMAC_SHA1 (/lib/x86_64-linux-gnu/libcrypto.so.3+0x1a19e5) (BuildId: f41db69553ac874b43c3ab46a4e0973d2405a1d1)
    #13 0x7f944a8a2e48  (/lib/x86_64-linux-gnu/libzip.so.4+0x12e48) (BuildId: 02d1d621ce8e46311d39fa109b824b70dc2a7e1e)
    #14 0x7f944a8a545a  (/lib/x86_64-linux-gnu/libzip.so.4+0x1545a) (BuildId: 02d1d621ce8e46311d39fa109b824b70dc2a7e1e)
    #15 0x7f944a898f8a  (/lib/x86_64-linux-gnu/libzip.so.4+0x8f8a) (BuildId: 02d1d621ce8e46311d39fa109b824b70dc2a7e1e)
    #16 0x7f944a8a3e91 in zip_source_open (/lib/x86_64-linux-gnu/libzip.so.4+0x13e91) (BuildId: 02d1d621ce8e46311d39fa109b824b70dc2a7e1e)
    #17 0x7f944a8a3e7f in zip_source_open (/lib/x86_64-linux-gnu/libzip.so.4+0x13e7f) (BuildId: 02d1d621ce8e46311d39fa109b824b70dc2a7e1e)
    #18 0x7f944a89c974 in zip_fopen_index_encrypted (/lib/x86_64-linux-gnu/libzip.so.4+0xc974) (BuildId: 02d1d621ce8e46311d39fa109b824b70dc2a7e1e)

SUMMARY: MemorySanitizer: use-of-uninitialized-value (/lib/x86_64-linux-gnu/libcrypto.so.3+0xe2197) (BuildId: f41db69553ac874b43c3ab46a4e0973d2405a1d1) in BIO_new_file
Exiting

最小复现代码 #

#include <stdio.h>
#include <stdlib.h>
#include <zip.h>
#define MAX_STRING_LEN 256

int main() {
  char* file = (char*)calloc(MAX_STRING_LEN, sizeof(char));
  if (scanf("%s", file) != 1) {
    fprintf(stderr, "Error reading file path\n");
    return EXIT_FAILURE;
  }

  int32_t error = EXIT_SUCCESS;
  zip_error_t zip_error;

  zip_t* zip = zip_open(file, ZIP_RDONLY, &error);
  free(file);

  if (zip == NULL) {
    zip_error_init_with_code(&zip_error, error);
    fprintf(stderr, "Failed to open zip archive: %s\n",
    zip_error_strerror(&zip_error));
    return EXIT_FAILURE;
  }

  zip_file_t* open_zip = zip_fopen_index_encrypted(zip, 0, ZIP_FL_ENC_GUESS,
  "0000"); // Change this String for the password of the Zip file
  if (open_zip == NULL) {
    zip_close(zip);
    return EXIT_FAILURE;
  } else {
    printf("Zip was opened\n");
  }
  zip_fclose(open_zip);
  zip_close(zip);
  return EXIT_SUCCESS;
}

编译命令 #

mkdir -p build/
clang -c -Wall -Wextra -g -fsanitize=memory -std=c17 -I. -I./build -MMD main.c -o build/main.o
mkdir -p bin/
clang -Wall -Wextra -g -fsanitize=memory -I. -I./bin -I./build build/main.o -o bin/zipmem -lzip

分析与解答 #

你的代码本身没有明显疏漏：

• 用calloc初始化了文件路径缓冲区，避免了未初始化内存风险
• 正确处理了所有库函数的返回值，资源释放逻辑完整
• 密码字符串是常量，不存在未初始化问题

这个告警不是你的代码导致的，而是依赖库的兼容性问题，具体原因如下：

1. 错误栈显示问题出在OpenSSL 3.x的BIO_new_file调用中，属于OpenSSL初始化加载配置文件的内部逻辑，和你的业务代码完全无关
2. Ubuntu 20.04默认使用OpenSSL 1.1.1，而22.04升级到了OpenSSL 3.x，这是两个环境表现不同的核心原因
3. MemorySanitizer对未初始化内存的检测极为严格，但系统预编译的OpenSSL库并没有用Msan编译，导致Msan无法追踪库内部的内存初始化状态，从而产生误报（或者库内部确实存在不影响功能的未初始化内存）

验证与解决建议 #

• 手动用Msan编译OpenSSL和libzip，再链接到你的程序，如果告警消失，就能确认是预编译库的问题
• 若不想重新编译库，可以添加Msan抑制规则，忽略OpenSSL相关的未初始化告警，不会影响对业务代码的检测
• 由于Valgrind和其他sanitizer都未报告问题，且程序运行正常，这个告警不影响实际功能，可暂时忽略

内容的提问来源于stack exchange，提问作者CodingQuestions