C/C 動(dòng)態(tài)檢測內(nèi)存錯(cuò)誤利器?-?ASan

時(shí)間：2021-11-11 14:21:25

關(guān)鍵字：內(nèi)存

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[導(dǎo)讀]來自公眾號：大胖聊編程作者：大胖ASan，即AddressSanitizer，是一個(gè)適用于c/c程序的動(dòng)態(tài)內(nèi)存錯(cuò)誤檢測器，它由一個(gè)編譯器檢測模塊（LLVMpass）和一個(gè)替換malloc函數(shù)的運(yùn)行時(shí)庫組成，在性能及檢測內(nèi)存錯(cuò)誤方面都優(yōu)于Valgrind，你值得擁有。一適用平臺在L...

來自公眾號：大胖聊編程
作者：大胖

ASan，即Address Sanitizer，是一個(gè)適用于c/c 程序的動(dòng)態(tài)內(nèi)存錯(cuò)誤檢測器，它由一個(gè)編譯器檢測模塊（LLVM pass）和一個(gè)替換malloc函數(shù)的運(yùn)行時(shí)庫組成，在性能及檢測內(nèi)存錯(cuò)誤方面都優(yōu)于Valgrind，你值得擁有。
一適用平臺在LLVM3.1版之后，ASan就是其的一個(gè)組成部分，所以所有適用LLVM的平臺，且llvm版本大于3.1的，都可以適用ASan來檢查c/c 內(nèi)存錯(cuò)誤。對于gcc，則是4.8版本之后才加入ASan，但是ASan的完整功能則是要gcc版本在4.9.2以上。

二強(qiáng)大功能ASan作為編譯器內(nèi)置功能，支持檢測各種內(nèi)存錯(cuò)誤：

緩沖區(qū)溢出?
① 堆內(nèi)存溢出
② 棧上內(nèi)存溢出
③ 全局區(qū)緩存溢出
懸空指針（引用）
① 使用釋放后的堆上內(nèi)存
② 使用返回的棧上內(nèi)存
③ 使用退出作用域的變量
非法釋放
① 重復(fù)釋放
② 無效釋放
內(nèi)存泄漏
初始化順序?qū)е碌膯栴}

ASan和Valgrind對比如下圖：

三如何使用

使用ASan時(shí)，只需gcc選項(xiàng)加上-fsanitize=address選項(xiàng)；
如果想要在使用asan的時(shí)候獲取更好的性能，可以加上O1或者更高的編譯優(yōu)化選項(xiàng)；
想要在錯(cuò)誤信息中讓棧追溯信息更友好，可以加上-fno-omit-frame-pointer選項(xiàng)。
本文針對linux x86-64平臺，gcc編譯器環(huán)境實(shí)驗(yàn)。

本文實(shí)驗(yàn)環(huán)境：

[root@yglocal ~]# lsb_release -aLSB Version: :core-4.1-amd64:core-4.1-noarchDistributor ID: CentOSDescription: CentOS Linux release 8.1.1911 (Core) Release: 8.1.1911Codename: Core[root@yglocal ~]# uname -r4.18.0-147.el8.x86_64[root@yglocal ~]# gcc --versiongcc (GCC) 8.3.1 20190507 (Red Hat 8.3.1-4)Copyright (C) 2018 Free Software Foundation, Inc.This is free software; see the source for copying conditions. There is NOwarranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE
在centos上使用ASan，編譯會報(bào)如下錯(cuò)誤（gcc 4.8.5）：

[root@localhost test]# gcc -g -O2 -fsanitize=address -fno-omit-frame-pointer hello.c /usr/bin/ld: cannot find /usr/lib64/libasan.so.0.0.0collect2: error: ld returned 1 exit status

安裝libasan即可：

[root@localhost test]# yum install libasan

注：ubuntu x86-64系統(tǒng)只需gcc版本高于4.8即可；但是在rhel/centos上使用ASan功能，除了gcc版本大于4.8之外，還需要安裝libasan。
下面針對內(nèi)存的幾種c/c 常見內(nèi)存錯(cuò)誤，編寫例子，看下ASan的檢測輸出情況：

1
堆緩沖區(qū)溢出

測試代碼：

[root@yglocal asan_test]# vi heap_ovf_test.c

#include #include #include

int main(){ char *heap_buf = (char*)malloc(32*sizeof(char)); memcpy(heap_buf 30, "overflow", 8); //在heap_buf的第30個(gè)字節(jié)開始，拷貝8個(gè)字符

free(heap_buf);

return 0;}
編譯并運(yùn)行：

[root@yglocal asan_test]# gcc -fsanitize=address -fno-omit-frame-pointer -o heap_ovf_test heap_ovf_test.c [root@yglocal asan_test]# ./heap_ovf_test =================================================================

==40602==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x603000000030 at pc 0x7f3de8f91a1d bp 0x7ffd4b4ebb60 sp 0x7ffd4b4eb308

WRITE of size 8 at 0x603000000030 thread T0 #0 0x7f3de8f91a1c (/lib64/libasan.so.5 0x40a1c) #1 0x400845 in main (/root/asan_test/heap_ovf_test 0x400845) #2 0x7f3de8bb1872 in __libc_start_main (/lib64/libc.so.6 0x23872) #3 0x40075d in _start (/root/asan_test/heap_ovf_test 0x40075d)

0x603000000030 is located 0 bytes to the right of 32-byte region [0x603000000010,0x603000000030)allocated by thread T0 here: #0 0x7f3de9040ba8 in __interceptor_malloc (/lib64/libasan.so.5 0xefba8) #1 0x400827 in main (/root/asan_test/heap_ovf_test 0x400827) #2 0x7f3de8bb1872 in __libc_start_main (/lib64/libc.so.6 0x23872)

SUMMARY: AddressSanitizer: heap-buffer-overflow (/lib64/libasan.so.5 0x40a1c) Shadow bytes around the buggy address: 0x0c067fff7fb0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0x0c067fff7fc0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0x0c067fff7fd0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0x0c067fff7fe0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0x0c067fff7ff0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00=>0x0c067fff8000: fa fa 00 00 00 00[fa]fa fa fa fa fa fa fa fa fa 0x0c067fff8010: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa 0x0c067fff8020: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa 0x0c067fff8030: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa 0x0c067fff8040: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa 0x0c067fff8050: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa faShadow byte legend (one shadow byte represents 8 application bytes): Addressable: 00 Partially addressable: 01 02 03 04 05 06 07 Heap left redzone: fa Freed heap region: fd Stack left redzone: f1 Stack mid redzone: f2 Stack right redzone: f3 Stack after return: f5 Stack use after scope: f8 Global redzone: f9 Global init order: f6 Poisoned by user: f7 Container overflow: fc Array cookie: ac Intra object redzone: bb ASan internal: fe Left alloca redzone: ca Right alloca redzone: cb==40602==ABORTING[root@yglocal asan_test]#
可以看到asan報(bào)錯(cuò)：==40602==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x603000000030 at xxxx,下面也列出了發(fā)生heap-buffer-overflow時(shí)的調(diào)用鏈及heap buffer在哪里申請的。

2
棧緩沖區(qū)溢出

測試代碼：

[root@yglocal asan_test]# vi stack_ovf_test.c

#include #include

int main(){ char stack_buf[4] = {0}; strcpy(stack_buf, "1234");

return 0;}
編譯并運(yùn)行：

[root@yglocal asan_test]# ./stack_ovf_test =================================================================

==38634==ERROR: AddressSanitizer: stack-buffer-overflow on address 0x7ffcf3d8b8d4 at pc 0x7f8714bbaa1d bp 0x7ffcf3d8b8a0 sp 0x7ffcf3d8b048

WRITE of size 5 at 0x7ffcf3d8b8d4 thread T0 #0 0x7f8714bbaa1c (/lib64/libasan.so.5 0x40a1c) #1 0x400949 in main (/root/asan_test/stack_ovf_test 0x400949) #2 0x7f87147da872 in __libc_start_main (/lib64/libc.so.6 0x23872) #3 0x4007cd in _start (/root/asan_test/stack_ovf_test 0x4007cd)

Address 0x7ffcf3d8b8d4 is located in stack of thread T0 at offset 36 in frame #0 0x400895 in main (/root/asan_test/stack_ovf_test 0x400895)

This frame has 1 object(s): [32, 36) 'stack_buf' <== Memory access at offset 36 overflows this variableHINT: this may be a false positive if your program uses some custom stack unwind mechanism or swapcontext (longjmp and C exceptions *are* supported)SUMMARY: AddressSanitizer: stack-buffer-overflow (/lib64/libasan.so.5 0x40a1c) Shadow bytes around the buggy address: 0x10001e7a96c0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0x10001e7a96d0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0x10001e7a96e0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0x10001e7a96f0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0x10001e7a9700: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00=>0x10001e7a9710: 00 00 00 00 00 00 f1 f1 f1 f1[04]f2 f2 f2 f3 f3 0x10001e7a9720: f3 f3 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0x10001e7a9730: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0x10001e7a9740: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0x10001e7a9750: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0x10001e7a9760: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00......

可以看到asan報(bào)錯(cuò)：==38634==ERROR: AddressSanitizer: stack-buffer-overflow on address 0x7ffcf3d8b8d4 at xxx，發(fā)生stack buffer overflow時(shí)函數(shù)的調(diào)用鏈信息。

3
使用懸空指針

測試代碼：

[root@yglocal asan_test]# vi dangling_pointer_test.c

#include #include #include

int main(){ char *p = (char*)malloc(32*sizeof(char)); free(p);

int a = p[1];

return 0;}編譯并運(yùn)行：

[root@yglocal asan_test]# gcc -fsanitize=address -fno-omit-frame-pointer -o dangling_pointer_test dangling_pointer_test.c

[root@yglocal asan_test]# ./dangling_pointer_test =================================================================

==83532==ERROR: AddressSanitizer: heap-use-after-free on address 0x603000000011 at pc 0x0000004007c4 bp 0x7ffd7f562760 sp 0x7ffd7f562750

READ of size 1 at 0x603000000011 thread T0 #0 0x4007c3 in main (/root/asan_test/dangling_pointer_test 0x4007c3) #1 0x7f56196cd872 in __libc_start_main (/lib64/libc.so.6 0x23872) #2 0x4006ad in _start (/root/asan_test/dangling_pointer_test 0x4006ad)

0x603000000011 is located 1 bytes inside of 32-byte region [0x603000000010,0x603000000030)freed by thread T0 here: #0 0x7f5619b5c7e0 in __interceptor_free (/lib64/libasan.so.5 0xef7e0) #1 0x400787 in main (/root/asan_test/dangling_pointer_test 0x400787) #2 0x7f56196cd872 in __libc_start_main (/lib64/libc.so.6 0x23872)

previously allocated by thread T0 here: #0 0x7f5619b5cba8 in __interceptor_malloc (/lib64/libasan.so.5 0xefba8) #1 0x400777 in main (/root/asan_test/dangling_pointer_test 0x400777) #2 0x7f56196cd872 in __libc_start_main (/lib64/libc.so.6 0x23872)

SUMMARY: AddressSanitizer: heap-use-after-free (/root/asan_test/dangling_pointer_test 0x4007c3) in mainShadow bytes around the buggy address: 0x0c067fff7fb0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0x0c067fff7fc0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0x0c067fff7fd0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0x0c067fff7fe0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0x0c067fff7ff0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00=>0x0c067fff8000: fa fa[fd]fd fd fd fa fa fa fa fa fa fa fa fa fa 0x0c067fff8010: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa 0x0c067fff8020: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa 0x0c067fff8030: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa 0x0c067fff8040: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa 0x0c067fff8050: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa faShadow byte legend (one shadow byte represents 8 application bytes):......
4
使用棧上返回的變量

[root@yglocal asan_test]# vi use-after-return.c

#include #include #include int *ptr;void get_pointer(){ int local[10]; ptr =


                
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