close-exec flag not working in 2.6.9?

From: Ben Greear (greearb_at_candelatech.com)
Date: 01/31/05

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    Date:	Sun, 30 Jan 2005 23:56:07 -0800
To: linux-kernel <linux-kernel@vger.kernel.org>

    As far as I can tell, close-exec is not working correctly in 2.6.9
    or 2.6.10-1.741_FC3smp.

    The attached program generates a file /tmp/cl_foo.output
    which has this data:

    [greear@grok ~]$ more /tmp/cl_foo.output
    total 5
    lrwx------ 1 greear greear 64 Jan 30 23:49 0 -> /dev/pts/3
    l-wx------ 1 greear greear 64 Jan 30 23:49 1 -> /tmp/cl_foo.output
    l-wx------ 1 greear greear 64 Jan 30 23:49 2 -> /tmp/cl_foo.output
    lr-x------ 1 greear greear 64 Jan 30 23:49 3 -> /etc/passwd
    lr-x------ 1 greear greear 64 Jan 30 23:49 4 -> /proc/7020/fd

    I would not expect to see the /etc/passwd entry since I marked
    it close-exec in the parent process before forking and running
    the system() command.

    Am I confused about things, or is this a real bug?

    Thanks,
    Ben 

    -- 
Ben Greear <greearb@candelatech.com>
Candela Technologies Inc  http://www.candelatech.com

    #include <unistd.h>
    #include <fcntl.h>
    #include <stdio.h>
    #include <fstream>
    #include <iostream>
    #include <stdlib.h>
    #include <errno.h>

    using namespace std;

    void close_exec(int s) {
       int flags;

       flags = fcntl(s, F_GETFL);
       flags |= (FD_CLOEXEC);
       if (fcntl(s, F_SETFL, flags) < 0) {
          cerr << "ERROR: fcntl, executing close_exec: " << strerror(errno)
               << endl;
       }
    }//close_exec

    int main() {
       ofstream script("/tmp/cl_foo.bash");
       script << "#!/bin/bash\nls -l /proc/self/fd > /tmp/cl_foo.output 2>&1\n";
       script.close();
       
       if (chmod("/tmp/cl_foo.bash",
                 S_IRUSR|S_IWUSR|S_IXUSR|S_IRGRP|S_IXGRP|S_IROTH|S_IXOTH) < 0) {
          cerr << "ERROR: Failed to chmod /tmp/cl_foo.bash, error: "
               << strerror(errno) << endl;
          exit(7);
       }

       int fd = open("/etc/passwd", O_RDONLY);
       if (fd < 0) {
          cerr << "ERROR: Failed to open /etc/passwd: " << strerror(errno) << endl;
       }
       else {
          close_exec(fd);
       }

       int rv = fork();
       if (rv < 0) {
          cerr << "ERROR from fork: " << strerror(errno) << endl;
       }
       else if (rv == 0) {
          // Child
          system("/tmp/cl_foo.bash");
          exit(7);
       }
       else {
          // parent, done
          sleep(5);
       }
       return 0;
    }//main

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  • Next message: Matt Mackall: "[PATCH 5/8] lib/sort: Replace open-coded O(pids**2) bubblesort in cpusets"