SELinux: allow userspace to read policy back out of the kernel
There is interest in being able to see what the actual policy is that was
loaded into the kernel. The patch creates a new selinuxfs file
/selinux/policy which can be read by userspace. The actual policy that is
loaded into the kernel will be written back out to userspace.
Signed-off-by: Eric Paris <eparis@redhat.com>
Signed-off-by: James Morris <jmorris@namei.org>
diff --git a/security/selinux/selinuxfs.c b/security/selinux/selinuxfs.c
index a2e7a85..8eb102c 100644
--- a/security/selinux/selinuxfs.c
+++ b/security/selinux/selinuxfs.c
@@ -68,6 +68,8 @@
static struct dentry *class_dir;
static unsigned long last_class_ino;
+static char policy_opened;
+
/* global data for policy capabilities */
static struct dentry *policycap_dir;
@@ -111,6 +113,7 @@
SEL_REJECT_UNKNOWN, /* export unknown reject handling to userspace */
SEL_DENY_UNKNOWN, /* export unknown deny handling to userspace */
SEL_STATUS, /* export current status using mmap() */
+ SEL_POLICY, /* allow userspace to read the in kernel policy */
SEL_INO_NEXT, /* The next inode number to use */
};
@@ -351,6 +354,97 @@
.llseek = generic_file_llseek,
};
+struct policy_load_memory {
+ size_t len;
+ void *data;
+};
+
+static int sel_open_policy(struct inode *inode, struct file *filp)
+{
+ struct policy_load_memory *plm = NULL;
+ int rc;
+
+ BUG_ON(filp->private_data);
+
+ mutex_lock(&sel_mutex);
+
+ rc = task_has_security(current, SECURITY__READ_POLICY);
+ if (rc)
+ goto err;
+
+ rc = -EBUSY;
+ if (policy_opened)
+ goto err;
+
+ rc = -ENOMEM;
+ plm = kzalloc(sizeof(*plm), GFP_KERNEL);
+ if (!plm)
+ goto err;
+
+ if (i_size_read(inode) != security_policydb_len()) {
+ mutex_lock(&inode->i_mutex);
+ i_size_write(inode, security_policydb_len());
+ mutex_unlock(&inode->i_mutex);
+ }
+
+ rc = security_read_policy(&plm->data, &plm->len);
+ if (rc)
+ goto err;
+
+ policy_opened = 1;
+
+ filp->private_data = plm;
+
+ mutex_unlock(&sel_mutex);
+
+ return 0;
+err:
+ mutex_unlock(&sel_mutex);
+
+ if (plm)
+ vfree(plm->data);
+ kfree(plm);
+ return rc;
+}
+
+static int sel_release_policy(struct inode *inode, struct file *filp)
+{
+ struct policy_load_memory *plm = filp->private_data;
+
+ BUG_ON(!plm);
+
+ policy_opened = 0;
+
+ vfree(plm->data);
+ kfree(plm);
+
+ return 0;
+}
+
+static ssize_t sel_read_policy(struct file *filp, char __user *buf,
+ size_t count, loff_t *ppos)
+{
+ struct policy_load_memory *plm = filp->private_data;
+ int ret;
+
+ mutex_lock(&sel_mutex);
+
+ ret = task_has_security(current, SECURITY__READ_POLICY);
+ if (ret)
+ goto out;
+
+ ret = simple_read_from_buffer(buf, count, ppos, plm->data, plm->len);
+out:
+ mutex_unlock(&sel_mutex);
+ return ret;
+}
+
+static const struct file_operations sel_policy_ops = {
+ .open = sel_open_policy,
+ .read = sel_read_policy,
+ .release = sel_release_policy,
+};
+
static ssize_t sel_write_load(struct file *file, const char __user *buf,
size_t count, loff_t *ppos)
@@ -1668,6 +1762,7 @@
[SEL_REJECT_UNKNOWN] = {"reject_unknown", &sel_handle_unknown_ops, S_IRUGO},
[SEL_DENY_UNKNOWN] = {"deny_unknown", &sel_handle_unknown_ops, S_IRUGO},
[SEL_STATUS] = {"status", &sel_handle_status_ops, S_IRUGO},
+ [SEL_POLICY] = {"policy", &sel_policy_ops, S_IRUSR},
/* last one */ {""}
};
ret = simple_fill_super(sb, SELINUX_MAGIC, selinux_files);