linux-kernel - Re: [PATCH] nextfd(2)

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Wed, 04 Apr 2012 13:10:12 -0400
From:	Colin Walters <walters@...bum.org>
To:	KOSAKI Motohiro <kosaki.motohiro@...il.com>
Cc:	"H. Peter Anvin" <hpa@...or.com>,
	Alexey Dobriyan <adobriyan@...il.com>,
	akpm@...ux-foundation.org, viro@...iv.linux.org.uk,
	torvalds@...ux-foundation.org, drepper@...il.com,
	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH] nextfd(2)

On Wed, 2012-04-04 at 09:31 -0700, KOSAKI Motohiro wrote:

> Ideally possible. but practically impossible. 2) people don't use a their
> own malloc. they only uses open sources alternative malloc. And, I think
> you have too narrowing concern. Even though malloc people adds a workaround,
> the standard inhibit to use it

What do you mean?  If as hpa says, the maintainer of e.g. google
tcmalloc added a call to pthread_atfork(), then code which uses
opendir() would start working.

>  and people may continue to use more dangerous
> RLIM_NOFILE loop. 1) I haven't seen _practical_ userland software uses such
> linux internal hacking. Almost all major software can run on multiple OSs.

Except that if you're using /proc/self/fd, you're already relying on
Linux-specific functionality.  So it's not burdensome to use "struct
linux_dirent" and O_DIRECTORY either.

In GLib we're presently doing the regular /proc+opendir() under
#ifdef __linux__:
http://git.gnome.org/browse/glib/tree/glib/gspawn.c#n932

Now I'd happily switch to hpa's fdwalk() implementation if I was aware
of someone using glib in combination with an alternative malloc hitting
this problem.

Basically I think hpa is right here, and it's not really worth adding
a new system call.

The thing is, even if it were added today, since we need to run on old
kernels, we'd have to carry the code to use the /proc trick
approximately forever.  And in the end all nextfd() would accomplish
would be a *third* case in the already messy ifdefs/fallbacks
in the various implementations of process spawning.

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/