Paolo Bonzini <bonzini@xxxxxxx> writes:
> 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, save 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));
> + }
> +
I may be misreading the patch but, this logic always opens /dev/null, if
nobody asked for *any* cmd->no_stdXXX and low 3 fds are occupied, and
worse, it keeps fd=3 open.
Making sure low fds 0, 1 and 2 are open is a good thing. I do not think
clobbering fd=3 is good.
Also shouldn't this be done only on the side that dup()s fds around,
i.e. in the child process after fork()? Why is this done for the parent?
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