Subject: Re: [PATCH v2] fix start_command() bug when stdin is closed

From: Johannes Sixt <[email-masked]>
Date: Mon, 25 Aug 2008 15:12:34 +0200

Paolo Bonzini schrieb:
> There is a problem in the use of dup2+close in start_command()
> when one or more of file descriptors 0/1/2 are closed.

"Karl Chen pointed out a problem..." (just to give due credit).

>  int start_command(struct child_process *cmd)
>  {
>  	int need_in, need_out, need_err;
>  	int fdin[2], fdout[2], fderr[2];
>  
>  	/*
> +	 * Make sure that all file descriptors <= 2 are open, otherwise we
> +	 * mess them up when dup'ing pipes onto stdin/stdout/stderr.  Since
> +	 * we are at it, open a file descriptor on /dev/null to use it later.
> +	 */
> +	if (devnull_fd == -1)
> +	  {
> +	    devnull_fd = open("/dev/null", O_RDWR);
> +	    while (devnull_fd >= 0 && devnull_fd <= 2)
> +	      devnull_fd = dup(devnull_fd);
> +	    if (devnull_fd == -1)
> +	      die("opening /dev/null failed (%s)", strerror(errno));
> +	  }

Except for the insane GNU style indentation ;-) this makes a lot of sense.

Acked-by: Johannes Sixt <[email-masked]>

The changes to the MINGW32 section are good (they pass the test suite).
Thanks for taking care of that.

-- Hannes