From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-ig0-f169.google.com ([209.85.213.169]) by bombadil.infradead.org with esmtps (Exim 4.80.1 #2 (Red Hat Linux)) id 1ZhNnP-0000fp-8E for linux-mtd@lists.infradead.org; Wed, 30 Sep 2015 20:16:12 +0000 Received: by igxx6 with SMTP id x6so39679267igx.1 for ; Wed, 30 Sep 2015 13:15:50 -0700 (PDT) From: Seth Forshee To: "Eric W. Biederman" , Paul Moore , Stephen Smalley , Eric Paris Cc: Alexander Viro , Serge Hallyn , Andy Lutomirski , linux-fsdevel@vger.kernel.org, linux-security-module@vger.kernel.org, selinux@tycho.nsa.gov, linux-kernel@vger.kernel.org, linux-mtd@lists.infradead.org, linux-bcache@vger.kernel.org, dm-devel@redhat.com, linux-raid@vger.kernel.org, Seth Forshee , James Morris , "Serge E. Hallyn" Subject: [PATCH 3/5] selinux: Add support for unprivileged mounts from user namespaces Date: Wed, 30 Sep 2015 15:15:12 -0500 Message-Id: <1443644116-41366-4-git-send-email-seth.forshee@canonical.com> In-Reply-To: <1443644116-41366-1-git-send-email-seth.forshee@canonical.com> References: <1443644116-41366-1-git-send-email-seth.forshee@canonical.com> List-Id: Linux MTD discussion mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Security labels from unprivileged mounts in user namespaces must be ignored. Force superblocks from user namespaces whose labeling behavior is to use xattrs to use mountpoint labeling instead. For the mountpoint label, default to converting the current task context into a form suitable for file objects, but also allow the policy writer to specify a different label through policy transition rules. Pieced together from code snippets provided by Stephen Smalley. Signed-off-by: Seth Forshee --- security/selinux/hooks.c | 23 +++++++++++++++++++++++ 1 file changed, 23 insertions(+) diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c index de05207eb665..09be1dc21e58 100644 --- a/security/selinux/hooks.c +++ b/security/selinux/hooks.c @@ -756,6 +756,28 @@ static int selinux_set_mnt_opts(struct super_block *sb, goto out; } } + + /* + * If this is a user namespace mount, no contexts are allowed + * on the command line and security labels must be ignored. + */ + if (sb->s_user_ns != &init_user_ns) { + if (context_sid || fscontext_sid || rootcontext_sid || + defcontext_sid) { + rc = -EACCES; + goto out; + } + if (sbsec->behavior == SECURITY_FS_USE_XATTR) { + sbsec->behavior = SECURITY_FS_USE_MNTPOINT; + rc = security_transition_sid(current_sid(), current_sid(), + SECCLASS_FILE, NULL, + &sbsec->mntpoint_sid); + if (rc) + goto out; + } + goto out_set_opts; + } + /* sets the context of the superblock for the fs being mounted. */ if (fscontext_sid) { rc = may_context_mount_sb_relabel(fscontext_sid, sbsec, cred); @@ -824,6 +846,7 @@ static int selinux_set_mnt_opts(struct super_block *sb, sbsec->def_sid = defcontext_sid; } +out_set_opts: rc = sb_finish_set_opts(sb); out: mutex_unlock(&sbsec->lock); -- 1.9.1