CODEWITHSUNDEEP
cdirectoryreaddir
certifiedNoob
certifiedNoob

Reputation: 365

Segfault calling readdir() - Directory Traversal

I thought this would be pretty academic but its not. I'm trying to traverse a directory try (recursively). However, I keep getting the following message when calling readdir():

 ./xsed.bin
 make: *** [run] Segmentation fault

GDB has the following output when tracing though the program:

Breakpoint 1, recurseDir (path=0x401090 ".") at xsed.c:216
216             DIR *currD = opendir(path);
(gdb) n
217             if( currD = NULL)
(gdb) n
226                     entry = readdir(currD);
(gdb) n

Program received signal SIGSEGV, Segmentation fault.
0x00007ffff7afef86 in __readdir (dirp=0x0) at ../sysdeps/unix/readdir.c:45
45      ../sysdeps/unix/readdir.c: No such file or directory.
    in ../sysdeps/unix/readdir.c

I've read several places never to call readdir() twice on the same Dir* object. I'm getting a segfault when calling it once. I've checked the path string to ensure its correct (e.g. using "." or "./" etc)-- no luck.

Here's the code below: Called like: recurseDir(getcwd(currD,256)) or recurseDir(".");

  void recurseDir(char *path)
  {

    DIR *currD = opendir(path);
    if( currD = NULL)
    {
            fprintf(stderr,"Could not open directory: %s\n",path);
            return;
    }
    else
    {
            struct dirent *entry;
            char *dName;
            entry = readdir(currD); <--- segfault

            if( entry == NULL)
            {
                    fprintf(stderr,"Error reading directory.\n");
                    return;
            }

            dName = entry->d_name;
            printf("Current dir:%s\n",dName);

      }
   }

I have no idea how the argument (dirp) is getting to be NULL inside the call to readdir(). NOTE: This is happening during the first call to recurseDir(), no recursion happens at all. I'm I off or is this a compiler/machine thing?

Please help!!!!

Upvotes: 0

Views: 3200

Answers (1)

jjlin
jjlin

Reputation: 4713

For one thing, you have if( currD = NULL). You probably meant == rather than =. Yep, that would definitely explain why your currD is NULL. :-)

By the way, some people prefer to write NULL == currD to guard against this. Or you could just say !currD.

Upvotes: 2

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