close-exec flag not working in 2.6.9?

close-exec flag not working in 2.6.9?

[Ben Greear]

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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


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#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

Re: close-exec flag not working in 2.6.9?

[Ulrich Drepper]

On Sun, 30 Jan 2005 23:56:07 -0800, Ben Greear <greearb@candelatech.com> wrote:
>    flags = fcntl(s, F_GETFL);
>    flags |= (FD_CLOEXEC);
>    if (fcntl(s, F_SETFL, flags) < 0) {

These have to be F_GETFD and F_SETFD respectively.  Note L -> D.

Re: close-exec flag not working in 2.6.9?

[Ben Greear]

Ulrich Drepper wrote:
> On Sun, 30 Jan 2005 23:56:07 -0800, Ben Greear <greearb@candelatech.com> wrote:
> 
>>   flags = fcntl(s, F_GETFL);
>>   flags |= (FD_CLOEXEC);
>>   if (fcntl(s, F_SETFL, flags) < 0) {
> 
> 
> These have to be F_GETFD and F_SETFD respectively.  Note L -> D.

Yes, that does seem to work much better.  It would have been
a while before I ever figured that out on my own.

Thanks to you and the other people who pointed that out
off the list!

Ben

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