Re: [PATCH] xl: close nullfd after dup2'ing it to stdin

[Wei Liu <wei.liu2@citrix.com>]

On Tue, Feb 16, 2016 at 11:35:45AM +0000, Ian Campbell wrote:
> Taking care not to do so if nullfd happens (somehow) to have the same
> fd number as stdin/out/err.
> 
> CID: 1130519
> 
> It was previously hypothesised[0] that fixing 1130516 would solve this
> too, but that appears to not have been the case.
> 
> Compile tested only.
> 
> [0] http://lists.xenproject.org/archives/html/xen-devel/2013-11/msg02931.html
> 
> Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
> Cc: andrew.cooper3@citrix.com

Acked-by: Wei Liu <wei.liu2@citrix.com>

> ---
>  tools/libxl/xl_cmdimpl.c | 10 ++++++++++
>  1 file changed, 10 insertions(+)
> 
> diff --git a/tools/libxl/xl_cmdimpl.c b/tools/libxl/xl_cmdimpl.c
> index d07ccb2..f38e3dd 100644
> --- a/tools/libxl/xl_cmdimpl.c
> +++ b/tools/libxl/xl_cmdimpl.c
> @@ -505,6 +505,16 @@ static int do_daemonize(char *name, const char *pidfile)
>      dup2(logfile, 1);
>      dup2(logfile, 2);
>  
> +    /* Close nullfd unless it happens to == std{in,out,err} */
> +    switch (nullfd) {
> +    case 0:
> +    case 1:
> +    case 2:
> +        break;
> +    default:
> +        close(nullfd);
> +    }
> +
>      CHK_SYSCALL(daemon(0, 1));
>  
>      if (pidfile) {
> -- 
> 2.1.4
>