C/C++ android 11 代码在 strstr api 调用时崩溃

Question

我遇到以下 strstr api 调用崩溃：

pid: 6640, tid: 6640, name: demoapp  >>> /vendor/bin/demoapp <<<
uid: 0
signal 11 (SIGSEGV), code 2 (SEGV_ACCERR), fault addr 0x7b8a91c000
    x0  b400007b8a91bf70  x1  0000000000000000  x2  000000000000002f  x3  b400007b8a91c000
    x4  0000000000000020  x5  0000000040100401  x6  0000000000000000  x7  454349564544200a
    x8  0000000000000074  x9  0000000000000010  x10 000000000000001f  x11 000000000000003a
    x12 000000000000008d  x13 000000000000006a  x14 00000000000000b5  x15 000000000000000a
    x16 0000007e7abd20e8  x17 0000007e7ab5e100  x18 0000007e7b35a000  x19 b400007b8a91befc
    x20 0000007fc35ae0b8  x21 0000007fc35add00  x22 00000000000000bf  x23 b400007b8a91bf70
    x24 0000007e7ae41000  x25 00000000000000b5  x26 00000000000000b4  x27 00000000000000b5
    x28 0000007fc35ae146  x29 0000007fc35add30
    lr  0000007e7aba9cc0  sp  0000007fc35ad4d0  pc  0000007e7ab5e160  pst 0000000020000000

backtrace:
      #00 pc 000000000004a160  /apex/com.android.runtime/lib64/bionic/libc.so (memchr_default+96) (BuildId: 229c19d159f619ab0dd102acf1afb05f)
      #01 pc 0000000000095cbc  /apex/com.android.runtime/lib64/bionic/libc.so (strstr+804) (BuildId: 229c19d159f619ab0dd102acf1afb05f)
      #02 pc 0000000000002714  /vendor/bin/demoapp (main+1740) (BuildId: 5f1858d36b95111200fa67ca2c2aefee)
      #03 pc 0000000000049080  /apex/com.android.runtime/lib64/bionic/libc.so (__libc_init+108) (BuildId: 229c19d159f619ab0dd102acf1afb05f)

代码崩溃解析如下：

bionic/libc/arch-arm64/default/bionic/memchr.S::114
109     b.ls    .Lmasklast
110     /* Have we found something already? */
111     cbnz    synd, .Ltail
112 
113 .Lloop:
114     ld1 {vdata1.16b, vdata2.16b}, [src], #32
115     subs    cntin, cntin, #32
116     cmeq    vhas_chr1.16b, vdata1.16b, vrepchr.16b
117     cmeq    vhas_chr2.16b, vdata2.16b, vrepchr.16b
118     /* If we're out of data we finish regardless of the result */
119     b.ls    .Lend
bionic/libc/include/bits/fortify/string.h::138
133 __BIONIC_FORTIFY_INLINE
134 void* memchr(const void* const s __pass_object_size, int c, size_t n) __overloadable {
135     size_t bos = __bos(s);
136 
137     if (__bos_trivially_ge(bos, n)) {
138         return __builtin_memchr(s, c, n);
139     }
140 
141     return __memchr_chk(s, c, n, bos);
142 }
143 
bionic/libc/upstream-openbsd/lib/libc/string/strstr.c::139
134     for (;;) {
135         /* Update incremental end-of-haystack pointer */
136         if (z-h < l) {
137             /* Fast estimate for MIN(l,63) */
138             size_t grow = l | 63;
139             const unsigned char *z2 = memchr(z, 0, grow);
140             if (z2) {
141                 z = z2;
142                 if (z-h < l) return 0;
143             } else z += grow;
144         }
bionic/libc/upstream-openbsd/lib/libc/string/strstr.c::195
190     if (!h[2]) return 0;
191     if (!n[3]) return threebyte_strstr((void *)h, (void *)n);
192     if (!h[3]) return 0;
193     if (!n[4]) return fourbyte_strstr((void *)h, (void *)n);
194 
195     return twoway_strstr((void *)h, (void *)n);
196 }
197 DEF_STRONG(strstr);
vendor/source/demoapp.c::37
37    bool ok = (bool)strstr(srcstr, deststr);

貌似srcstr和deststr都不是NULL，issue不易重现，只能分析stack来寻找线索了！

如果不是 NULL 指针问题，那么还有其他原因会导致 strstr 崩溃吗？

Answer 1

function strstr()崩溃的最常见原因是：

• 如果提供的char*之一是nullptr ，
• 如果提供的char*之一指向没有'\0'终止符的字符串。
• 如果提供的char*之一发生缓冲区溢出。

还有很多其他可能的原因。 如果这没有帮助，请提供出现问题的代码。