linux-kernel - Re: [fuse-devel] [PATCH v4 4/5] fuse: Support privileged xattrs only with a mount option

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, 21 Oct 2014 14:44:31 -0700
From:	Andy Lutomirski <luto@...capital.net>
To:	Michael j Theall <mtheall@...ibm.com>
Cc:	"Eric W. Biederman" <ebiederm@...ssion.com>,
	fuse-devel@...ts.sourceforge.net,
	Linux FS Devel <linux-fsdevel@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Miklos Szeredi <miklos@...redi.hu>,
	"Serge H. Hallyn" <serge.hallyn@...ntu.com>
Subject: Re: [fuse-devel] [PATCH v4 4/5] fuse: Support privileged xattrs only
 with a mount option

On Tue, Oct 21, 2014 at 2:34 PM, Michael j Theall <mtheall@...ibm.com> wrote:
> Andy Lutomirski <luto@...capital.net> wrote on 10/21/2014 04:27:13 PM:
>> But how does this help with FUSE at all?   Does FUSE end up calling
>> xattr_permission?
>>
>> --Andy
>>
>
> The xattr system calls go through xattr_permission before it ever gets to
> the FUSE ops.

But a malicious FUSE filesystem can just put those xattrs there by
fiat, the same way that my old FUSE-based sploit put a setuid root
copy of bash in the filesystem.  No setxattr calls are needed.

--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/