selinux: Add support for unprivileged mounts from user namespaces (aad82892) · Commits · 戴 / test

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 <seth.forshee@canonical.com> Acked-by:

Stephen Smalley <sds@tycho.nsa.gov> Acked-by:

James Morris <james.l.morris@oracle.com> Signed-off-by:

Eric W. Biederman <ebiederm@xmission.com>

security/selinux/hooks.c

+23 −0

Original line number	Diff line number	Diff line
		@@ -830,6 +830,28 @@ 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);
		@@ -898,6 +920,7 @@ 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);

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