On Fri, Dec 02, 2016 at 08:41:21AM +0100, Samuel Thibault wrote:
> About the port leak in select discussed on IRC, I checked history a bit,
> this (000ef460744786571f51604e6de631b7168e239a):
>
> - if (d[i].type)
> + if (d[i].type & ~SELECT_ERROR)
> __mach_port_destroy (__mach_task_self (), d[i].reply_port);
>
> was added when handling EBADF , for which there is no reply port to
> destroy. Then I added this (099f8d2b7ecedc4f6fc895d2c35912f995289c24):
Indeed, so type != 0 doesn't imply port creation.
> I guess we could simply do this:
>
> for (i = firstfd; i <= lastfd; ++i)
> - if (d[i].type & ~SELECT_ERROR)
> + if (d[i].type & SELECT_ERROR)
> + {
> + d[i].reply_port = MACH_PORT_NULL;
> + }
> else
> {
> int type = d[i].type;
> d[i].reply_port = __mach_reply_port ();
>
> as well as in the error case of __io_select_request, and then just check
> against MACH_PORT_NULL before destroy.
So the condition would look like
if (d[i].type && (d[i].reply_port != MACH_PORT_NULL))
I agree.
In the mean time, I've built libc packages that partially fix the issue
(there will still be spurious destruction attempts on EBADF, which could
destroy a legitimate right) but the leak is so severe I found it useful.
If you want those, add
deb http://ftp.sceen.net/debian sid main
to sources.list, and add the GPG key D50E6AD4 to APT.
--
Richard Braun
