linux-kernel - Re: How is pivot_root intended to be used?

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:	Tue, 02 Sep 2014 12:53:14 -0700
From:	Andy Lutomirski <luto@...capital.net>
To:	Steven Stewart-Gallus <sstewartgallus00@...angara.bc.ca>,
	linux-kernel@...r.kernel.org
Subject: Re: How is pivot_root intended to be used?

On 09/01/2014 02:19 PM, Steven Stewart-Gallus wrote:
> Hello,
>
> I am not confused about how I can currently use pivot_root for
> containers on my kernel (version 3.13). Currently a sequence like:
>
>      if (-1 == syscall(__NR_pivot_root, ".", ".")) {
>          perror("pivot_root");
>          return EXIT_FAILURE;
>      }
>
>      if (-1 == umount2(".", MNT_DETACH)) {
>          perror("umount");
>          return EXIT_FAILURE;

Given the comment, you don't know what '.' refers to in the umount2 call 
above.  In fact, I think you're actually detaching the wrong thing, 
leaving possible security issues.

See:

https://github.com/sandstorm-io/sandstorm/blob/master/src/sandstorm/supervisor-main.c%2B%2B#L922

for a program that does this more carefully.

--Andy
--
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/