fuse changes chown to?

Question

i m trying to modify fuse example to mount any directory. I want to mount /home/nikhil in tmp. i ran it as, $ ./ni /home/nikhil tmp

It mounts tmp folder, but cannot access it.

$ls -ltr tmp 

ls: cannot access tmp: Operation not permitted

$ ls -ltr

ls: cannot access delete: Operation not permitted total 11716 d????????? ? ? ? ? ? delete

My code is

#define FUSE_USE_VERSION 26

#include <fuse.h>
#include <stdio.h>
#include <string.h>
#include <errno.h>
#include <fcntl.h>
#include <stdlib.h>
#include <limits.h>
#include <unistd.h>

#define MAX 100
char *rootpath;

static void ni_fullpath(char fpath[MAX], const char *path){
    strcpy(fpath, rootpath);
    strncat(fpath, path, MAX);
}

static int ni_getattr(const char *path, struct stat *stbuf)
{
int res = 0;
char fpath[MAX];
memset(stbuf, 0, sizeof(struct stat));
    ni_fullpath(fpath, path);
res = lstat(fpath, stbuf);
return res;
}

static int ni_readdir(const char *path, void *buf, fuse_fill_dir_t filler,
         off_t offset, struct fuse_file_info *fi)
{
(void) offset;
(void) fi;
// i didnt understand this
filler(buf, ".", NULL, 0);
filler(buf, "..", NULL, 0);
    ni_fullpath(fpath, path);
filler(buf, fpath + 1, NULL, 0);

return 0;
}

static int ni_open(const char *path, struct fuse_file_info *fi)
{
int fd;
char fpath[MAX];
ni_fullpath(fpath, path);
if ((fi->flags & 3) != O_RDONLY)
    return -EACCES;

fd = open(fpath, fi->flags);
return fd;
}

static int ni_read(const char *path, char *buf, size_t size, off_t offset,
          struct fuse_file_info *fi)
{
return pread(fi->fh, buf, size, offset);

}

static struct fuse_operations ni_oper = {
.getattr    = ni_getattr,
.readdir    = ni_readdir,
.open       = ni_open,
.read       = ni_read,    
};


void ni_usage(){
fprintf(stderr, "usage ni rootDir mountPoint");
abort();
}

int main(int argc, char *argv[])
{
printf("%s %s \n", argv[1], argv[2]);
rootpath = realpath(argv[1], NULL);

argv[1] = argv[2];
argc--;
return fuse_main(argc, argv, &ni_oper, NULL);
}   

Can anybody help what i m doing wrong ? I m using ubuntu 1104 64 bit.

Answer 1

How about using uninitialized var fpath instead of path?

static int ni_getattr(const char *path, struct stat *stbuf)
{
   int res = 0;
   char fpath[MAX];
   memset(stbuf, 0, sizeof(struct stat));

   res = lstat(fpath, stbuf);
   return res;
} 

You probably missed ni_fullpath(fpath, path);

And as far as I understand the 0 should be returned in open callback if success, so it should look like:

   ....
   fd = open(fpath, fi->flags);
   if (fd < 0)
       return -errno;
   fi->fh = fd;
   return 0;
}

List operation should uses readdir callback, and in your case it has very limited application. It'd be better to start code on the basis of fusexmp. Check how readdir is implemented there.