From: Stephen Smalley <sds@tycho.nsa.gov>
To: Jann Horn <jannh@google.com>, Paul Moore <paul@paul-moore.com>,
Eric Paris <eparis@parisplace.org>,
selinux@tycho.nsa.gov
Cc: James Morris <jmorris@namei.org>,
"Serge E. Hallyn" <serge@hallyn.com>,
linux-security-module@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] selinux: stricter parsing in mls_context_to_sid()
Date: Mon, 6 Aug 2018 08:58:47 -0400 [thread overview]
Message-ID: <a4c0b0a6-3331-1abc-266c-7e6589a04208@tycho.nsa.gov> (raw)
In-Reply-To: <20180803093604.38254-1-jannh@google.com>
On 08/03/2018 05:36 AM, Jann Horn wrote:
> mls_context_to_sid incorrectly accepted MLS context strings that are
> followed by a dash and trailing garbage.
>
> Before this change, the following command works:
>
> # mount -t tmpfs -o 'context=system_u:object_r:tmp_t:s0-s0:c0-BLAH' \
> none mount
>
> After this change, it fails with the following error message in dmesg:
>
> SELinux: security_context_str_to_sid(system_u:object_r:tmp_t:s0-s0:c0-BLAH)
> failed for (dev tmpfs, type tmpfs) errno=-22
>
> This is not an important bug; but it is a small quirk that was useful for
> exploiting a vulnerability in fusermount.
>
> This patch does not change the behavior when the policy does not have MLS
> enabled.
>
> Signed-off-by: Jann Horn <jannh@google.com>
Acked-by: Stephen Smalley <sds@tycho.nsa.gov>
> ---
> security/selinux/ss/mls.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/security/selinux/ss/mls.c b/security/selinux/ss/mls.c
> index 39475fb455bc..2c73d612d2ee 100644
> --- a/security/selinux/ss/mls.c
> +++ b/security/selinux/ss/mls.c
> @@ -344,7 +344,7 @@ int mls_context_to_sid(struct policydb *pol,
> break;
> }
> }
> - if (delim == '-') {
> + if (delim == '-' && l == 0) {
> /* Extract high sensitivity. */
> scontextp = p;
> while (*p && *p != ':')
>
prev parent reply other threads:[~2018-08-06 13:10 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-08-03 9:36 [PATCH] selinux: stricter parsing in mls_context_to_sid() Jann Horn
2018-08-04 0:01 ` Paul Moore
2018-08-06 19:47 ` Jann Horn
2018-08-06 12:58 ` Stephen Smalley [this message]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=a4c0b0a6-3331-1abc-266c-7e6589a04208@tycho.nsa.gov \
--to=sds@tycho.nsa.gov \
--cc=eparis@parisplace.org \
--cc=jannh@google.com \
--cc=jmorris@namei.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-security-module@vger.kernel.org \
--cc=paul@paul-moore.com \
--cc=selinux@tycho.nsa.gov \
--cc=serge@hallyn.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).