释放字符串中的内存释放 "invalid next size (fast)"

Question

我正在修改一些http服务器代码，这是一个发送文件或目录列表的功能。我不断收到此错误提示存在内存问题：

    *** Error in `./a.out': free(): invalid next size (fast): 
    0x08b85200 ***
    ======= Backtrace: =========
    /usr/lib/libc.so.6(+0x69923)[0xb7677923]
    /usr/lib/libc.so.6(+0x6fc47)[0xb767dc47]
    /usr/lib/libc.so.6(+0x70401)[0xb767e401]
    ./a.out[0x8049093]
    ./a.out[0x8049455]
    ./a.out[0x804952d]
    ./a.out[0x804964e]
    /usr/lib/libc.so.6(__libc_start_main+0xf7)[0xb7626497]
    ./a.out[0x8048a51]
    ======= Memory map: ========
    08048000-0804a000 r-xp 00000000 08:01 3147464    /home/baroc/Desktop/HW3/part3/a.out
    0804a000-0804b000 rw-p 00001000 08:01 3147464    /home/baroc/Desktop/HW3/part3/a.out
    08b85000-08ba6000 rw-p 00000000 00:00 0          [heap]
    b7400000-b7421000 rw-p 00000000 00:00 0 
    b7421000-b7500000 ---p 00000000 00:00 0 
    b75df000-b75fb000 r-xp 00000000 08:01 1183170    /usr/lib/libgcc_s.so.1
    b75fb000-b75fc000 rw-p 0001b000 08:01 1183170    /usr/lib/libgcc_s.so.1
    b760d000-b760e000 rw-p 00000000 00:00 0 
    b760e000-b77c1000 r-xp 00000000 08:01 1182850    /usr/lib/libc-2.22.so
    b77c1000-b77c2000 ---p 001b3000 08:01 1182850    /usr/lib/libc-2.22.so
    b77c2000-b77c4000 r--p 001b3000 08:01 1182850    /usr/lib/libc-2.22.so
    b77c4000-b77c5000 rw-p 001b5000 08:01 1182850    /usr/lib/libc-2.22.so
    b77c5000-b77c8000 rw-p 00000000 00:00 0 
    b77d7000-b77d9000 rw-p 00000000 00:00 0 
    b77d9000-b77da000 rw-p 00000000 00:00 0 
    b77da000-b77dc000 r--p 00000000 00:00 0          [vvar]
    b77dc000-b77dd000 r-xp 00000000 00:00 0          [vdso]
    b77dd000-b77ff000 r-xp 00000000 08:01 1182848    /usr/lib/ld-2.22.so
    b77ff000-b7800000 r--p 00021000 08:01 1182848    /usr/lib/ld-2.22.so
    b7800000-b7801000 rw-p 00022000 08:01 1182848    /usr/lib/ld-2.22.so
    bfc06000-bfc27000 rw-p 00000000 00:00 0          [stack]

这是我的代码：

    static int handleFileRequest(
            const char *webRoot, const char *requestURI, int clntSock)
    {

        int statusCode;
        FILE *fp = NULL;
        char *file = (char *)malloc(strlen(webRoot) + strlen(requestURI) + 100);

        if (file == NULL)
            die("malloc failed");
        strcpy(file, webRoot);
        strcat(file, requestURI);
        struct stat st;
        if (file[strlen(file)-1] == '/') {
            char *tfile = (char *)malloc(strlen(file));
            strcpy(tfile, file);
            strcat(tfile,"index.html");
            if(stat(tfile, &st) != 0){
                int fd[2];
                pid_t pid;
                if(pipe(fd)<0)
                    die("pipe() failed when list dir");
                if((pid = fork())<0){
                    die("fork failed when list dir");
                }else if(pid>0){
                    close(fd[0]);
                    if(fd[1]!=STDOUT_FILENO){
                        if(dup2(fd[1],STDOUT_FILENO)!=STDOUT_FILENO)
                            die("dup2 error to stdout");
                    }
                    close(fd[1]);
                    if(execl("/bin/ls", "ls", file, NULL)<0)
                        die("error execl ls");
                    close(fd[1]);
                    if(waitpid(pid, NULL, 0)<0){
                        die("waitpid error");
                    }
                    exit(0);
                }else{
                    close(fd[1]);
                    int n;
                    char wline[DISK_IO_BUF_SIZE];
                    while ((n = read(fd[0], wline, sizeof(wline))) > 0) {
                        if (send(clntSock, wline, n, 0) != n) {
                            perror("\nsend() failed");
                            break;
                        }
                    }
                    close(fd[0]);
                    exit(0);
                }

                free(tfile);
                goto func_end;
            }else{
                strcat(file, "index.html");
                free(tfile);
            }
        }
        //change this part for identifying a directory

        if (stat(file, &st) == 0 && S_ISDIR(st.st_mode)) {
            statusCode = 403; // "Forbidden"
            sendStatusLine(clntSock, statusCode);
            goto func_end;
        }
        fp = fopen(file, "rb");

        if (fp == NULL) {
            statusCode = 404; // "Not Found"
            sendStatusLine(clntSock, statusCode);
            goto func_end;
        }
        statusCode = 200; // "OK"
        sendStatusLine(clntSock, statusCode);
        size_t n;
        char buf[DISK_IO_BUF_SIZE];
        while ((n = fread(buf, 1, sizeof(buf), fp)) > 0) {
            if (send(clntSock, buf, n, 0) != n) {
                perror("\nsend() failed");
                break;
            }
        }
        if (ferror(fp))
            perror("fread failed");
    func_end:
        // clean up
        free(file);
        if (fp)
            fclose(fp);
        return statusCode;
    }

当我尝试访问其中包含 "index.html" 的目录时出现问题。像 /test/，其中有 /test/index.html

看来问题出在代码末尾的"free(file);"。当我注释掉它时，我的 Mac 上的运行没有错误，但 linux 上仍然有错误。我不明白我哪里做错了。请有人帮助我！

我按照建议使用了 valgrind，这就是我得到的结果：

    --1936-- REDIR: 0x40ba300 (libc.so.6:malloc) redirected to 0x402a129 (malloc)
    --1936-- REDIR: 0x40c0060 (libc.so.6:__GI_memchr) redirected to 0x402e100 (__GI_memchr)
    --1936-- REDIR: 0x40c0d50 (libc.so.6:__GI_memcpy) redirected to 0x402ea20 (__GI_memcpy)
    ==1936== embedded gdbserver: reading from /tmp/vgdb-pipe-from-vgdb-to-1936-by-baroc-on-???
    ==1936== embedded gdbserver: writing to   /tmp/vgdb-pipe-to-vgdb-from-1936-by-baroc-on-???
    ==1936== embedded gdbserver: shared mem   /tmp/vgdb-pipe-shared-mem-vgdb-1936-by-baroc-on-???
    ==1936== 
    ==1936== TO CONTROL THIS PROCESS USING vgdb (which you probably
    ==1936== don't want to do, unless you know exactly what you're doing,
    ==1936== or are doing some strange experiment):
    ==1936==   /usr/lib/valgrind/../../bin/vgdb --pid=1936 ...command...
    ==1936== 
    ==1936== TO DEBUG THIS PROCESS USING GDB: start GDB like this
    ==1936==   /path/to/gdb ./a.out
    ==1936== and then give GDB the following command
    ==1936==   target remote | /usr/lib/valgrind/../../bin/vgdb --pid=1936
    ==1936== --pid is optional if only one valgrind process is running
    ==1936== 
    --1936-- REDIR: 0x40be450 (libc.so.6:strcmp) redirected to 0x402555d (_vgnU_ifunc_wrapper)
    --1936-- REDIR: 0x417e340 (libc.so.6:__strcmp_ssse3) redirected to 0x402de80 (strcmp)
    --1936-- REDIR: 0x40beb20 (libc.so.6:strlen) redirected to 0x402555d (_vgnU_ifunc_wrapper)
    --1936-- REDIR: 0x40c7c80 (libc.so.6:__strlen_sse2_bsf) redirected to 0x402cda0 (strlen)
    --1936-- REDIR: 0x40bf970 (libc.so.6:strstr) redirected to 0x4031220 (strstr)
    --1936-- REDIR: 0x40be510 (libc.so.6:strcpy) redirected to 0x402555d (_vgnU_ifunc_wrapper)
    --1936-- REDIR: 0x40c7e50 (libc.so.6:__strcpy_ssse3) redirected to 0x402ce80 (strcpy)
    --1936-- REDIR: 0x40be030 (libc.so.6:strcat) redirected to 0x402555d (_vgnU_ifunc_wrapper)
    --1936-- REDIR: 0x40d3410 (libc.so.6:__strcat_ssse3) redirected to 0x402ca60 (strcat)
    ==1936== Invalid write of size 1
    ==1936==    at 0x402CEC5: strcpy (in /usr/lib/valgrind/vgpreload_memcheck-x86-linux.so)
    ==1936==    by 0x8048E63: handleFileRequest (in /home/baroc/Desktop/HW3/part3/a.out)
    ==1936==    by 0x804947E: doProcess (in /home/baroc/Desktop/HW3/part3/a.out)
    ==1936==    by 0x8049556: doFork (in /home/baroc/Desktop/HW3/part3/a.out)
    ==1936==    by 0x8049677: main (in /home/baroc/Desktop/HW3/part3/a.out)
    ==1936==  Address 0x420229a is 0 bytes after a block of size 42 alloc'd
    ==1936==    at 0x402A1AE: malloc (in /usr/lib/valgrind/vgpreload_memcheck-x86-linux.so)
    ==1936==    by 0x8048E4F: handleFileRequest (in /home/baroc/Desktop/HW3/part3/a.out)
    ==1936==    by 0x804947E: doProcess (in /home/baroc/Desktop/HW3/part3/a.out)
    ==1936==    by 0x8049556: doFork (in /home/baroc/Desktop/HW3/part3/a.out)
    ==1936==    by 0x8049677: main (in /home/baroc/Desktop/HW3/part3/a.out)
    ==1936== 
    ==1936== Invalid read of size 1
    ==1936==    at 0x8048E78: handleFileRequest (in /home/baroc/Desktop/HW3/part3/a.out)
    ==1936==    by 0x804947E: doProcess (in /home/baroc/Desktop/HW3/part3/a.out)
    ==1936==    by 0x8049556: doFork (in /home/baroc/Desktop/HW3/part3/a.out)
    ==1936==    by 0x8049677: main (in /home/baroc/Desktop/HW3/part3/a.out)
    ==1936==  Address 0x420229a is 0 bytes after a block of size 42 alloc'd
    ==1936==    at 0x402A1AE: malloc (in /usr/lib/valgrind/vgpreload_memcheck-x86-linux.so)
    ==1936==    by 0x8048E4F: handleFileRequest (in /home/baroc/Desktop/HW3/part3/a.out)
    ==1936==    by 0x804947E: doProcess (in /home/baroc/Desktop/HW3/part3/a.out)
    ==1936==    by 0x8049556: doFork (in /home/baroc/Desktop/HW3/part3/a.out)
    ==1936==    by 0x8049677: main (in /home/baroc/Desktop/HW3/part3/a.out)
    ==1936== 
    ==1936== Invalid write of size 4
    ==1936==    at 0x8048E86: handleFileRequest (in /home/baroc/Desktop/HW3/part3/a.out)
    ==1936==    by 0x804947E: doProcess (in /home/baroc/Desktop/HW3/part3/a.out)
    ==1936==    by 0x8049556: doFork (in /home/baroc/Desktop/HW3/part3/a.out)
    ==1936==    by 0x8049677: main (in /home/baroc/Desktop/HW3/part3/a.out)
    ==1936==  Address 0x420229a is 0 bytes after a block of size 42 alloc'd
    ==1936==    at 0x402A1AE: malloc (in /usr/lib/valgrind/vgpreload_memcheck-x86-linux.so)
    ==1936==    by 0x8048E4F: handleFileRequest (in /home/baroc/Desktop/HW3/part3/a.out)
    ==1936==    by 0x804947E: doProcess (in /home/baroc/Desktop/HW3/part3/a.out)
    ==1936==    by 0x8049556: doFork (in /home/baroc/Desktop/HW3/part3/a.out)
    ==1936==    by 0x8049677: main (in /home/baroc/Desktop/HW3/part3/a.out)
    ==1936== 
    ==1936== Invalid write of size 4
    ==1936==    at 0x8048E8C: handleFileRequest (in /home/baroc/Desktop/HW3/part3/a.out)
    ==1936==    by 0x804947E: doProcess (in /home/baroc/Desktop/HW3/part3/a.out)
    ==1936==    by 0x8049556: doFork (in /home/baroc/Desktop/HW3/part3/a.out)
    ==1936==    by 0x8049677: main (in /home/baroc/Desktop/HW3/part3/a.out)
    ==1936==  Address 0x420229e is 4 bytes after a block of size 42 alloc'd
    ==1936==    at 0x402A1AE: malloc (in /usr/lib/valgrind/vgpreload_memcheck-x86-linux.so)
    ==1936==    by 0x8048E4F: handleFileRequest (in /home/baroc/Desktop/HW3/part3/a.out)
    ==1936==    by 0x804947E: doProcess (in /home/baroc/Desktop/HW3/part3/a.out)
    ==1936==    by 0x8049556: doFork (in /home/baroc/Desktop/HW3/part3/a.out)
    ==1936==    by 0x8049677: main (in /home/baroc/Desktop/HW3/part3/a.out)
    ==1936== 
    ==1936== Invalid write of size 2
    ==1936==    at 0x8048E93: handleFileRequest (in /home/baroc/Desktop/HW3/part3/a.out)
    ==1936==    by 0x804947E: doProcess (in /home/baroc/Desktop/HW3/part3/a.out)
    ==1936==    by 0x8049556: doFork (in /home/baroc/Desktop/HW3/part3/a.out)
    ==1936==    by 0x8049677: main (in /home/baroc/Desktop/HW3/part3/a.out)
    ==1936==  Address 0x42022a2 is 8 bytes after a block of size 42 alloc'd
    ==1936==    at 0x402A1AE: malloc (in /usr/lib/valgrind/vgpreload_memcheck-x86-linux.so)
    ==1936==    by 0x8048E4F: handleFileRequest (in /home/baroc/Desktop/HW3/part3/a.out)
    ==1936==    by 0x804947E: doProcess (in /home/baroc/Desktop/HW3/part3/a.out)
    ==1936==    by 0x8049556: doFork (in /home/baroc/Desktop/HW3/part3/a.out)
    ==1936==    by 0x8049677: main (in /home/baroc/Desktop/HW3/part3/a.out)
    ==1936== 
    ==1936== Invalid write of size 1
    ==1936==    at 0x8048E99: handleFileRequest (in /home/baroc/Desktop/HW3/part3/a.out)
    ==1936==    by 0x804947E: doProcess (in /home/baroc/Desktop/HW3/part3/a.out)
    ==1936==    by 0x8049556: doFork (in /home/baroc/Desktop/HW3/part3/a.out)
    ==1936==    by 0x8049677: main (in /home/baroc/Desktop/HW3/part3/a.out)
    ==1936==  Address 0x42022a4 is 10 bytes after a block of size 42 alloc'd
    ==1936==    at 0x402A1AE: malloc (in /usr/lib/valgrind/vgpreload_memcheck-x86-linux.so)
    ==1936==    by 0x8048E4F: handleFileRequest (in /home/baroc/Desktop/HW3/part3/a.out)
    ==1936==    by 0x804947E: doProcess (in /home/baroc/Desktop/HW3/part3/a.out)
    ==1936==    by 0x8049556: doFork (in /home/baroc/Desktop/HW3/part3/a.out)
    ==1936==    by 0x8049677: main (in /home/baroc/Desktop/HW3/part3/a.out)
    ==1936== 
    ==1936== Syscall param stat64(file_name) points to unaddressable byte(s)
    ==1936==    at 0x411F42A: _xstat (in /usr/lib/libc-2.22.so)
    ==1936==    by 0x804970D: stat (in /home/baroc/Desktop/HW3/part3/a.out)
    ==1936==    by 0x8048EAB: handleFileRequest (in /home/baroc/Desktop/HW3/part3/a.out)
    ==1936==    by 0x804947E: doProcess (in /home/baroc/Desktop/HW3/part3/a.out)
    ==1936==    by 0x8049556: doFork (in /home/baroc/Desktop/HW3/part3/a.out)
    ==1936==    by 0x8049677: main (in /home/baroc/Desktop/HW3/part3/a.out)
    ==1936==  Address 0x420229a is 0 bytes after a block of size 42 alloc'd
    ==1936==    at 0x402A1AE: malloc (in /usr/lib/valgrind/vgpreload_memcheck-x86-linux.so)
    ==1936==    by 0x8048E4F: handleFileRequest (in /home/baroc/Desktop/HW3/part3/a.out)
    ==1936==    by 0x804947E: doProcess (in /home/baroc/Desktop/HW3/part3/a.out)
    ==1936==    by 0x8049556: doFork (in /home/baroc/Desktop/HW3/part3/a.out)
    ==1936==    by 0x8049677: main (in /home/baroc/Desktop/HW3/part3/a.out)
    ==1936== 
    --1936-- REDIR: 0x40ba950 (libc.so.6:free) redirected to 0x402b101 (free)
    --1936-- REDIR: 0x40c2960 (libc.so.6:strchrnul) redirected to 0x4030bd0 (strchrnul)
    1936 127.0.0.1 "GET /test/test2/ HTTP/1.1" 200 OK
    ==1936== 
    ==1936== HEAP SUMMARY:
    ==1936==     in use at exit: 0 bytes in 0 blocks
    ==1936==   total heap usage: 4 allocs, 4 frees, 872 bytes allocated
    ==1936== 
    ==1936== All heap blocks were freed -- no leaks are possible
    ==1936== 
    ==1936== ERROR SUMMARY: 8 errors from 7 contexts (suppressed: 0 from 0)
    ==1936== 
    ==1936== 1 errors in context 1 of 7:
    ==1936== Syscall param stat64(file_name) points to unaddressable byte(s)
    ==1936==    at 0x411F42A: _xstat (in /usr/lib/libc-2.22.so)
    ==1936==    by 0x804970D: stat (in /home/baroc/Desktop/HW3/part3/a.out)
    ==1936==    by 0x8048EAB: handleFileRequest (in /home/baroc/Desktop/HW3/part3/a.out)
    ==1936==    by 0x804947E: doProcess (in /home/baroc/Desktop/HW3/part3/a.out)
    ==1936==    by 0x8049556: doFork (in /home/baroc/Desktop/HW3/part3/a.out)
    ==1936==    by 0x8049677: main (in /home/baroc/Desktop/HW3/part3/a.out)
    ==1936==  Address 0x420229a is 0 bytes after a block of size 42 alloc'd
    ==1936==    at 0x402A1AE: malloc (in /usr/lib/valgrind/vgpreload_memcheck-x86-linux.so)
    ==1936==    by 0x8048E4F: handleFileRequest (in /home/baroc/Desktop/HW3/part3/a.out)
    ==1936==    by 0x804947E: doProcess (in /home/baroc/Desktop/HW3/part3/a.out)
    ==1936==    by 0x8049556: doFork (in /home/baroc/Desktop/HW3/part3/a.out)
    ==1936==    by 0x8049677: main (in /home/baroc/Desktop/HW3/part3/a.out)
    ==1936== 
    ==1936== 
    ==1936== 1 errors in context 2 of 7:
    ==1936== Invalid write of size 1
    ==1936==    at 0x8048E99: handleFileRequest (in /home/baroc/Desktop/HW3/part3/a.out)
    ==1936==    by 0x804947E: doProcess (in /home/baroc/Desktop/HW3/part3/a.out)
    ==1936==    by 0x8049556: doFork (in /home/baroc/Desktop/HW3/part3/a.out)
    ==1936==    by 0x8049677: main (in /home/baroc/Desktop/HW3/part3/a.out)
    ==1936==  Address 0x42022a4 is 10 bytes after a block of size 42 alloc'd
    ==1936==    at 0x402A1AE: malloc (in /usr/lib/valgrind/vgpreload_memcheck-x86-linux.so)
    ==1936==    by 0x8048E4F: handleFileRequest (in /home/baroc/Desktop/HW3/part3/a.out)
    ==1936==    by 0x804947E: doProcess (in /home/baroc/Desktop/HW3/part3/a.out)
    ==1936==    by 0x8049556: doFork (in /home/baroc/Desktop/HW3/part3/a.out)
    ==1936==    by 0x8049677: main (in /home/baroc/Desktop/HW3/part3/a.out)
    ==1936== 
    ==1936== 
    ==1936== 1 errors in context 3 of 7:
    ==1936== Invalid write of size 4
    ==1936==    at 0x8048E8C: handleFileRequest (in /home/baroc/Desktop/HW3/part3/a.out)
    ==1936==    by 0x804947E: doProcess (in /home/baroc/Desktop/HW3/part3/a.out)
    ==1936==    by 0x8049556: doFork (in /home/baroc/Desktop/HW3/part3/a.out)
    ==1936==    by 0x8049677: main (in /home/baroc/Desktop/HW3/part3/a.out)
    ==1936==  Address 0x420229e is 4 bytes after a block of size 42 alloc'd
    ==1936==    at 0x402A1AE: malloc (in /usr/lib/valgrind/vgpreload_memcheck-x86-linux.so)
    ==1936==    by 0x8048E4F: handleFileRequest (in /home/baroc/Desktop/HW3/part3/a.out)
    ==1936==    by 0x804947E: doProcess (in /home/baroc/Desktop/HW3/part3/a.out)
    ==1936==    by 0x8049556: doFork (in /home/baroc/Desktop/HW3/part3/a.out)
    ==1936==    by 0x8049677: main (in /home/baroc/Desktop/HW3/part3/a.out)
    ==1936== 
    ==1936== 
    ==1936== 1 errors in context 4 of 7:
    ==1936== Invalid write of size 4
    ==1936==    at 0x8048E86: handleFileRequest (in /home/baroc/Desktop/HW3/part3/a.out)
    ==1936==    by 0x804947E: doProcess (in /home/baroc/Desktop/HW3/part3/a.out)
    ==1936==    by 0x8049556: doFork (in /home/baroc/Desktop/HW3/part3/a.out)
    ==1936==    by 0x8049677: main (in /home/baroc/Desktop/HW3/part3/a.out)
    ==1936==  Address 0x420229a is 0 bytes after a block of size 42 alloc'd
    ==1936==    at 0x402A1AE: malloc (in /usr/lib/valgrind/vgpreload_memcheck-x86-linux.so)
    ==1936==    by 0x8048E4F: handleFileRequest (in /home/baroc/Desktop/HW3/part3/a.out)
    ==1936==    by 0x804947E: doProcess (in /home/baroc/Desktop/HW3/part3/a.out)
    ==1936==    by 0x8049556: doFork (in /home/baroc/Desktop/HW3/part3/a.out)
    ==1936==    by 0x8049677: main (in /home/baroc/Desktop/HW3/part3/a.out)
    ==1936== 
    ==1936== 
    ==1936== 1 errors in context 5 of 7:
    ==1936== Invalid read of size 1
    ==1936==    at 0x8048E78: handleFileRequest (in /home/baroc/Desktop/HW3/part3/a.out)
    ==1936==    by 0x804947E: doProcess (in /home/baroc/Desktop/HW3/part3/a.out)
    ==1936==    by 0x8049556: doFork (in /home/baroc/Desktop/HW3/part3/a.out)
    ==1936==    by 0x8049677: main (in /home/baroc/Desktop/HW3/part3/a.out)
    ==1936==  Address 0x420229a is 0 bytes after a block of size 42 alloc'd
    ==1936==    at 0x402A1AE: malloc (in /usr/lib/valgrind/vgpreload_memcheck-x86-linux.so)
    ==1936==    by 0x8048E4F: handleFileRequest (in /home/baroc/Desktop/HW3/part3/a.out)
    ==1936==    by 0x804947E: doProcess (in /home/baroc/Desktop/HW3/part3/a.out)
    ==1936==    by 0x8049556: doFork (in /home/baroc/Desktop/HW3/part3/a.out)
    ==1936==    by 0x8049677: main (in /home/baroc/Desktop/HW3/part3/a.out)
    ==1936== 
    ==1936== 
    ==1936== 1 errors in context 6 of 7:
    ==1936== Invalid write of size 1
    ==1936==    at 0x402CEC5: strcpy (in /usr/lib/valgrind/vgpreload_memcheck-x86-linux.so)
    ==1936==    by 0x8048E63: handleFileRequest (in /home/baroc/Desktop/HW3/part3/a.out)
    ==1936==    by 0x804947E: doProcess (in /home/baroc/Desktop/HW3/part3/a.out)
    ==1936==    by 0x8049556: doFork (in /home/baroc/Desktop/HW3/part3/a.out)
    ==1936==    by 0x8049677: main (in /home/baroc/Desktop/HW3/part3/a.out)
    ==1936==  Address 0x420229a is 0 bytes after a block of size 42 alloc'd
    ==1936==    at 0x402A1AE: malloc (in /usr/lib/valgrind/vgpreload_memcheck-x86-linux.so)
    ==1936==    by 0x8048E4F: handleFileRequest (in /home/baroc/Desktop/HW3/part3/a.out)
    ==1936==    by 0x804947E: doProcess (in /home/baroc/Desktop/HW3/part3/a.out)
    ==1936==    by 0x8049556: doFork (in /home/baroc/Desktop/HW3/part3/a.out)
    ==1936==    by 0x8049677: main (in /home/baroc/Desktop/HW3/part3/a.out)
    ==1936== 
    ==1936== 
    ==1936== 2 errors in context 7 of 7:
    ==1936== Invalid write of size 2
    ==1936==    at 0x8048E93: handleFileRequest (in /home/baroc/Desktop/HW3/part3/a.out)
    ==1936==    by 0x804947E: doProcess (in /home/baroc/Desktop/HW3/part3/a.out)
    ==1936==    by 0x8049556: doFork (in /home/baroc/Desktop/HW3/part3/a.out)
    ==1936==    by 0x8049677: main (in /home/baroc/Desktop/HW3/part3/a.out)
    ==1936==  Address 0x42022a2 is 8 bytes after a block of size 42 alloc'd
    ==1936==    at 0x402A1AE: malloc (in /usr/lib/valgrind/vgpreload_memcheck-x86-linux.so)
    ==1936==    by 0x8048E4F: handleFileRequest (in /home/baroc/Desktop/HW3/part3/a.out)
    ==1936==    by 0x804947E: doProcess (in /home/baroc/Desktop/HW3/part3/a.out)
    ==1936==    by 0x8049556: doFork (in /home/baroc/Desktop/HW3/part3/a.out)
    ==1936==    by 0x8049677: main (in /home/baroc/Desktop/HW3/part3/a.out)
    ==1936== 
    ==1936== ERROR SUMMARY: 8 errors from 7 contexts (suppressed: 0 from 0)

Answer 1

      ...
if (file[strlen(file)-1] == '/') {
            char *tfile = (char *)malloc(strlen(file));
            strcpy(tfile, file);
            strcat(tfile,"index.html");
      ...

tfile 分配的大小与 file 的长度相同。 tfile 获取 file 中的所有内容，加上分配结束后的空终止符。 tfile 与更多内容连接，超出其分配的容量。

释放字符串中的内存释放 "invalid next size (fast)"

Memory Free "invalid next size (fast)" in freeing string

c

memory

free