1 files changed, 446 insertions, 2 deletions

diff --git a/kernel/seccomp.c b/kernel/seccomp.c
index 393e029f778a..15b6be97fc09 100644
--- a/kernel/seccomp.c
+++ b/kernel/seccomp.c
@@ -33,12 +33,74 @@
 #endif
 
 #ifdef CONFIG_SECCOMP_FILTER
+#include <linux/file.h>
 #include <linux/filter.h>
 #include <linux/pid.h>
 #include <linux/ptrace.h>
 #include <linux/security.h>
 #include <linux/tracehook.h>
 #include <linux/uaccess.h>
+#include <linux/anon_inodes.h>
+
+enum notify_state {
+	SECCOMP_NOTIFY_INIT,
+	SECCOMP_NOTIFY_SENT,
+	SECCOMP_NOTIFY_REPLIED,
+};
+
+struct seccomp_knotif {
+	/* The struct pid of the task whose filter triggered the notification */
+	struct task_struct *task;
+
+	/* The "cookie" for this request; this is unique for this filter. */
+	u64 id;
+
+	/*
+	 * The seccomp data. This pointer is valid the entire time this
+	 * notification is active, since it comes from __seccomp_filter which
+	 * eclipses the entire lifecycle here.
+	 */
+	const struct seccomp_data *data;
+
+	/*
+	 * Notification states. When SECCOMP_RET_USER_NOTIF is returned, a
+	 * struct seccomp_knotif is created and starts out in INIT. Once the
+	 * handler reads the notification off of an FD, it transitions to SENT.
+	 * If a signal is received the state transitions back to INIT and
+	 * another message is sent. When the userspace handler replies, state
+	 * transitions to REPLIED.
+	 */
+	enum notify_state state;
+
+	/* The return values, only valid when in SECCOMP_NOTIFY_REPLIED */
+	int error;
+	long val;
+
+	/* Signals when this has entered SECCOMP_NOTIFY_REPLIED */
+	struct completion ready;
+
+	struct list_head list;
+};
+
+/**
+ * struct notification - container for seccomp userspace notifications. Since
+ * most seccomp filters will not have notification listeners attached and this
+ * structure is fairly large, we store the notification-specific stuff in a
+ * separate structure.
+ *
+ * @request: A semaphore that users of this notification can wait on for
+ *           changes. Actual reads and writes are still controlled with
+ *           filter->notify_lock.
+ * @next_id: The id of the next request.
+ * @notifications: A list of struct seccomp_knotif elements.
+ * @wqh: A wait queue for poll.
+ */
+struct notification {
+	struct semaphore request;
+	u64 next_id;
+	struct list_head notifications;
+	wait_queue_head_t wqh;
+};
 
 /**
  * struct seccomp_filter - container for seccomp BPF programs
@@ -50,6 +112,8 @@
  * @log: true if all actions except for SECCOMP_RET_ALLOW should be logged
  * @prev: points to a previously installed, or inherited, filter
  * @prog: the BPF program to evaluate
+ * @notif: the struct that holds all notification related information
+ * @notify_lock: A lock for all notification-related accesses.
  *
  * seccomp_filter objects are organized in a tree linked via the @prev
  * pointer.  For any task, it appears to be a singly-linked list starting
@@ -66,6 +130,8 @@ struct seccomp_filter {
 	bool log;
 	struct seccomp_filter *prev;
 	struct bpf_prog *prog;
+	struct notification *notif;
+	struct mutex notify_lock;
 };
 
 /* Limit any path through the tree to 256KB worth of instructions. */
@@ -386,6 +452,7 @@ static struct seccomp_filter *seccomp_prepare_filter(struct sock_fprog *fprog)
 	if (!sfilter)
 		return ERR_PTR(-ENOMEM);
 
+	mutex_init(&sfilter->notify_lock);
 	ret = bpf_prog_create_from_user(&sfilter->prog, fprog,
 					seccomp_check_filter, save_orig);
 	if (ret < 0) {
@@ -479,7 +546,6 @@ static long seccomp_attach_filter(unsigned int flags,
 
 static void __get_seccomp_filter(struct seccomp_filter *filter)
 {
-	/* Reference count is bounded by the number of total processes. */
 	refcount_inc(&filter->usage);
 }
 
@@ -550,11 +616,13 @@ static void seccomp_send_sigsys(int syscall, int reason)
 #define SECCOMP_LOG_TRACE		(1 << 4)
 #define SECCOMP_LOG_LOG			(1 << 5)
 #define SECCOMP_LOG_ALLOW		(1 << 6)
+#define SECCOMP_LOG_USER_NOTIF		(1 << 7)
 
 static u32 seccomp_actions_logged = SECCOMP_LOG_KILL_PROCESS |
 				    SECCOMP_LOG_KILL_THREAD  |
 				    SECCOMP_LOG_TRAP  |
 				    SECCOMP_LOG_ERRNO |
+				    SECCOMP_LOG_USER_NOTIF |
 				    SECCOMP_LOG_TRACE |
 				    SECCOMP_LOG_LOG;
 
@@ -575,6 +643,9 @@ static inline void seccomp_log(unsigned long syscall, long signr, u32 action,
 	case SECCOMP_RET_TRACE:
 		log = requested && seccomp_actions_logged & SECCOMP_LOG_TRACE;
 		break;
+	case SECCOMP_RET_USER_NOTIF:
+		log = requested && seccomp_actions_logged & SECCOMP_LOG_USER_NOTIF;
+		break;
 	case SECCOMP_RET_LOG:
 		log = seccomp_actions_logged & SECCOMP_LOG_LOG;
 		break;
@@ -646,6 +717,68 @@ void secure_computing_strict(int this_syscall)
 #else
 
 #ifdef CONFIG_SECCOMP_FILTER
+static u64 seccomp_next_notify_id(struct seccomp_filter *filter)
+{
+	/*
+	 * Note: overflow is ok here, the id just needs to be unique per
+	 * filter.
+	 */
+	lockdep_assert_held(&filter->notify_lock);
+	return filter->notif->next_id++;
+}
+
+static void seccomp_do_user_notification(int this_syscall,
+					 struct seccomp_filter *match,
+					 const struct seccomp_data *sd)
+{
+	int err;
+	long ret = 0;
+	struct seccomp_knotif n = {};
+
+	mutex_lock(&match->notify_lock);
+	err = -ENOSYS;
+	if (!match->notif)
+		goto out;
+
+	n.task = current;
+	n.state = SECCOMP_NOTIFY_INIT;
+	n.data = sd;
+	n.id = seccomp_next_notify_id(match);
+	init_completion(&n.ready);
+	list_add(&n.list, &match->notif->notifications);
+
+	up(&match->notif->request);
+	wake_up_poll(&match->notif->wqh, EPOLLIN | EPOLLRDNORM);
+	mutex_unlock(&match->notify_lock);
+
+	/*
+	 * This is where we wait for a reply from userspace.
+	 */
+	err = wait_for_completion_interruptible(&n.ready);
+	mutex_lock(&match->notify_lock);
+	if (err == 0) {
+		ret = n.val;
+		err = n.error;
+	}
+
+	/*
+	 * Note that it's possible the listener died in between the time when
+	 * we were notified of a respons (or a signal) and when we were able to
+	 * re-acquire the lock, so only delete from the list if the
+	 * notification actually exists.
+	 *
+	 * Also note that this test is only valid because there's no way to
+	 * *reattach* to a notifier right now. If one is added, we'll need to
+	 * keep track of the notif itself and make sure they match here.
+	 */
+	if (match->notif)
+		list_del(&n.list);
+out:
+	mutex_unlock(&match->notify_lock);
+	syscall_set_return_value(current, task_pt_regs(current),
+				 err, ret);
+}
+
 static int __seccomp_filter(int this_syscall, const struct seccomp_data *sd,
 			    const bool recheck_after_trace)
 {
@@ -728,6 +861,10 @@ static int __seccomp_filter(int this_syscall, const struct seccomp_data *sd,
 
 		return 0;
 
+	case SECCOMP_RET_USER_NOTIF:
+		seccomp_do_user_notification(this_syscall, match, sd);
+		goto skip;
+
 	case SECCOMP_RET_LOG:
 		seccomp_log(this_syscall, 0, action, true);
 		return 0;
@@ -834,6 +971,263 @@ out:
 }
 
 #ifdef CONFIG_SECCOMP_FILTER
+static int seccomp_notify_release(struct inode *inode, struct file *file)
+{
+	struct seccomp_filter *filter = file->private_data;
+	struct seccomp_knotif *knotif;
+
+	mutex_lock(&filter->notify_lock);
+
+	/*
+	 * If this file is being closed because e.g. the task who owned it
+	 * died, let's wake everyone up who was waiting on us.
+	 */
+	list_for_each_entry(knotif, &filter->notif->notifications, list) {
+		if (knotif->state == SECCOMP_NOTIFY_REPLIED)
+			continue;
+
+		knotif->state = SECCOMP_NOTIFY_REPLIED;
+		knotif->error = -ENOSYS;
+		knotif->val = 0;
+
+		complete(&knotif->ready);
+	}
+
+	kfree(filter->notif);
+	filter->notif = NULL;
+	mutex_unlock(&filter->notify_lock);
+	__put_seccomp_filter(filter);
+	return 0;
+}
+
+static long seccomp_notify_recv(struct seccomp_filter *filter,
+				void __user *buf)
+{
+	struct seccomp_knotif *knotif = NULL, *cur;
+	struct seccomp_notif unotif;
+	ssize_t ret;
+
+	memset(&unotif, 0, sizeof(unotif));
+
+	ret = down_interruptible(&filter->notif->request);
+	if (ret < 0)
+		return ret;
+
+	mutex_lock(&filter->notify_lock);
+	list_for_each_entry(cur, &filter->notif->notifications, list) {
+		if (cur->state == SECCOMP_NOTIFY_INIT) {
+			knotif = cur;
+			break;
+		}
+	}
+
+	/*
+	 * If we didn't find a notification, it could be that the task was
+	 * interrupted by a fatal signal between the time we were woken and
+	 * when we were able to acquire the rw lock.
+	 */
+	if (!knotif) {
+		ret = -ENOENT;
+		goto out;
+	}
+
+	unotif.id = knotif->id;
+	unotif.pid = task_pid_vnr(knotif->task);
+	unotif.data = *(knotif->data);
+
+	knotif->state = SECCOMP_NOTIFY_SENT;
+	wake_up_poll(&filter->notif->wqh, EPOLLOUT | EPOLLWRNORM);
+	ret = 0;
+out:
+	mutex_unlock(&filter->notify_lock);
+
+	if (ret == 0 && copy_to_user(buf, &unotif, sizeof(unotif))) {
+		ret = -EFAULT;
+
+		/*
+		 * Userspace screwed up. To make sure that we keep this
+		 * notification alive, let's reset it back to INIT. It
+		 * may have died when we released the lock, so we need to make
+		 * sure it's still around.
+		 */
+		knotif = NULL;
+		mutex_lock(&filter->notify_lock);
+		list_for_each_entry(cur, &filter->notif->notifications, list) {
+			if (cur->id == unotif.id) {
+				knotif = cur;
+				break;
+			}
+		}
+
+		if (knotif) {
+			knotif->state = SECCOMP_NOTIFY_INIT;
+			up(&filter->notif->request);
+		}
+		mutex_unlock(&filter->notify_lock);
+	}
+
+	return ret;
+}
+
+static long seccomp_notify_send(struct seccomp_filter *filter,
+				void __user *buf)
+{
+	struct seccomp_notif_resp resp = {};
+	struct seccomp_knotif *knotif = NULL, *cur;
+	long ret;
+
+	if (copy_from_user(&resp, buf, sizeof(resp)))
+		return -EFAULT;
+
+	if (resp.flags)
+		return -EINVAL;
+
+	ret = mutex_lock_interruptible(&filter->notify_lock);
+	if (ret < 0)
+		return ret;
+
+	list_for_each_entry(cur, &filter->notif->notifications, list) {
+		if (cur->id == resp.id) {
+			knotif = cur;
+			break;
+		}
+	}
+
+	if (!knotif) {
+		ret = -ENOENT;
+		goto out;
+	}
+
+	/* Allow exactly one reply. */
+	if (knotif->state != SECCOMP_NOTIFY_SENT) {
+		ret = -EINPROGRESS;
+		goto out;
+	}
+
+	ret = 0;
+	knotif->state = SECCOMP_NOTIFY_REPLIED;
+	knotif->error = resp.error;
+	knotif->val = resp.val;
+	complete(&knotif->ready);
+out:
+	mutex_unlock(&filter->notify_lock);
+	return ret;
+}
+
+static long seccomp_notify_id_valid(struct seccomp_filter *filter,
+				    void __user *buf)
+{
+	struct seccomp_knotif *knotif = NULL;
+	u64 id;
+	long ret;
+
+	if (copy_from_user(&id, buf, sizeof(id)))
+		return -EFAULT;
+
+	ret = mutex_lock_interruptible(&filter->notify_lock);
+	if (ret < 0)
+		return ret;
+
+	ret = -ENOENT;
+	list_for_each_entry(knotif, &filter->notif->notifications, list) {
+		if (knotif->id == id) {
+			if (knotif->state == SECCOMP_NOTIFY_SENT)
+				ret = 0;
+			goto out;
+		}
+	}
+
+out:
+	mutex_unlock(&filter->notify_lock);
+	return ret;
+}
+
+static long seccomp_notify_ioctl(struct file *file, unsigned int cmd,
+				 unsigned long arg)
+{
+	struct seccomp_filter *filter = file->private_data;
+	void __user *buf = (void __user *)arg;
+
+	switch (cmd) {
+	case SECCOMP_IOCTL_NOTIF_RECV:
+		return seccomp_notify_recv(filter, buf);
+	case SECCOMP_IOCTL_NOTIF_SEND:
+		return seccomp_notify_send(filter, buf);
+	case SECCOMP_IOCTL_NOTIF_ID_VALID:
+		return seccomp_notify_id_valid(filter, buf);
+	default:
+		return -EINVAL;
+	}
+}
+
+static __poll_t seccomp_notify_poll(struct file *file,
+				    struct poll_table_struct *poll_tab)
+{
+	struct seccomp_filter *filter = file->private_data;
+	__poll_t ret = 0;
+	struct seccomp_knotif *cur;
+
+	poll_wait(file, &filter->notif->wqh, poll_tab);
+
+	ret = mutex_lock_interruptible(&filter->notify_lock);
+	if (ret < 0)
+		return EPOLLERR;
+
+	list_for_each_entry(cur, &filter->notif->notifications, list) {
+		if (cur->state == SECCOMP_NOTIFY_INIT)
+			ret |= EPOLLIN | EPOLLRDNORM;
+		if (cur->state == SECCOMP_NOTIFY_SENT)
+			ret |= EPOLLOUT | EPOLLWRNORM;
+		if ((ret & EPOLLIN) && (ret & EPOLLOUT))
+			break;
+	}
+
+	mutex_unlock(&filter->notify_lock);
+
+	return ret;
+}
+
+static const struct file_operations seccomp_notify_ops = {
+	.poll = seccomp_notify_poll,
+	.release = seccomp_notify_release,
+	.unlocked_ioctl = seccomp_notify_ioctl,
+};
+
+static struct file *init_listener(struct seccomp_filter *filter)
+{
+	struct file *ret = ERR_PTR(-EBUSY);
+	struct seccomp_filter *cur;
+
+	for (cur = current->seccomp.filter; cur; cur = cur->prev) {
+		if (cur->notif)
+			goto out;
+	}
+
+	ret = ERR_PTR(-ENOMEM);
+	filter->notif = kzalloc(sizeof(*(filter->notif)), GFP_KERNEL);
+	if (!filter->notif)
+		goto out;
+
+	sema_init(&filter->notif->request, 0);
+	filter->notif->next_id = get_random_u64();
+	INIT_LIST_HEAD(&filter->notif->notifications);
+	init_waitqueue_head(&filter->notif->wqh);
+
+	ret = anon_inode_getfile("seccomp notify", &seccomp_notify_ops,
+				 filter, O_RDWR);
+	if (IS_ERR(ret))
+		goto out_notif;
+
+	/* The file has a reference to it now */
+	__get_seccomp_filter(filter);
+
+out_notif:
+	if (IS_ERR(ret))
+		kfree(filter->notif);
+out:
+	return ret;
+}
+
 /**
  * seccomp_set_mode_filter: internal function for setting seccomp filter
  * @flags:  flags to change filter behavior
@@ -853,6 +1247,8 @@ static long seccomp_set_mode_filter(unsigned int flags,
 	const unsigned long seccomp_mode = SECCOMP_MODE_FILTER;
 	struct seccomp_filter *prepared = NULL;
 	long ret = -EINVAL;
+	int listener = -1;
+	struct file *listener_f = NULL;
 
 	/* Validate flags. */
 	if (flags & ~SECCOMP_FILTER_FLAG_MASK)
@@ -863,13 +1259,28 @@ static long seccomp_set_mode_filter(unsigned int flags,
 	if (IS_ERR(prepared))
 		return PTR_ERR(prepared);
 
+	if (flags & SECCOMP_FILTER_FLAG_NEW_LISTENER) {
+		listener = get_unused_fd_flags(O_CLOEXEC);
+		if (listener < 0) {
+			ret = listener;
+			goto out_free;
+		}
+
+		listener_f = init_listener(prepared);
+		if (IS_ERR(listener_f)) {
+			put_unused_fd(listener);
+			ret = PTR_ERR(listener_f);
+			goto out_free;
+		}
+	}
+
 	/*
 	 * Make sure we cannot change seccomp or nnp state via TSYNC
 	 * while another thread is in the middle of calling exec.
 	 */
 	if (flags & SECCOMP_FILTER_FLAG_TSYNC &&
 	    mutex_lock_killable(&current->signal->cred_guard_mutex))
-		goto out_free;
+		goto out_put_fd;
 
 	spin_lock_irq(&current->sighand->siglock);
 
@@ -887,6 +1298,16 @@ out:
 	spin_unlock_irq(&current->sighand->siglock);
 	if (flags & SECCOMP_FILTER_FLAG_TSYNC)
 		mutex_unlock(&current->signal->cred_guard_mutex);
+out_put_fd:
+	if (flags & SECCOMP_FILTER_FLAG_NEW_LISTENER) {
+		if (ret < 0) {
+			fput(listener_f);
+			put_unused_fd(listener);
+		} else {
+			fd_install(listener, listener_f);
+			ret = listener;
+		}
+	}
 out_free:
 	seccomp_filter_free(prepared);
 	return ret;
@@ -911,6 +1332,7 @@ static long seccomp_get_action_avail(const char __user *uaction)
 	case SECCOMP_RET_KILL_THREAD:
 	case SECCOMP_RET_TRAP:
 	case SECCOMP_RET_ERRNO:
+	case SECCOMP_RET_USER_NOTIF:
 	case SECCOMP_RET_TRACE:
 	case SECCOMP_RET_LOG:
 	case SECCOMP_RET_ALLOW:
@@ -922,6 +1344,20 @@ static long seccomp_get_action_avail(const char __user *uaction)
 	return 0;
 }
 
+static long seccomp_get_notif_sizes(void __user *usizes)
+{
+	struct seccomp_notif_sizes sizes = {
+		.seccomp_notif = sizeof(struct seccomp_notif),
+		.seccomp_notif_resp = sizeof(struct seccomp_notif_resp),
+		.seccomp_data = sizeof(struct seccomp_data),
+	};
+
+	if (copy_to_user(usizes, &sizes, sizeof(sizes)))
+		return -EFAULT;
+
+	return 0;
+}
+
 /* Common entry point for both prctl and syscall. */
 static long do_seccomp(unsigned int op, unsigned int flags,
 		       void __user *uargs)
@@ -938,6 +1374,11 @@ static long do_seccomp(unsigned int op, unsigned int flags,
 			return -EINVAL;
 
 		return seccomp_get_action_avail(uargs);
+	case SECCOMP_GET_NOTIF_SIZES:
+		if (flags != 0)
+			return -EINVAL;
+
+		return seccomp_get_notif_sizes(uargs);
 	default:
 		return -EINVAL;
 	}
@@ -1111,6 +1552,7 @@ long seccomp_get_metadata(struct task_struct *task,
 #define SECCOMP_RET_KILL_THREAD_NAME	"kill_thread"
 #define SECCOMP_RET_TRAP_NAME		"trap"
 #define SECCOMP_RET_ERRNO_NAME		"errno"
+#define SECCOMP_RET_USER_NOTIF_NAME	"user_notif"
 #define SECCOMP_RET_TRACE_NAME		"trace"
 #define SECCOMP_RET_LOG_NAME		"log"
 #define SECCOMP_RET_ALLOW_NAME		"allow"
@@ -1120,6 +1562,7 @@ static const char seccomp_actions_avail[] =
 				SECCOMP_RET_KILL_THREAD_NAME	" "
 				SECCOMP_RET_TRAP_NAME		" "
 				SECCOMP_RET_ERRNO_NAME		" "
+				SECCOMP_RET_USER_NOTIF_NAME     " "
 				SECCOMP_RET_TRACE_NAME		" "
 				SECCOMP_RET_LOG_NAME		" "
 				SECCOMP_RET_ALLOW_NAME;
@@ -1134,6 +1577,7 @@ static const struct seccomp_log_name seccomp_log_names[] = {
 	{ SECCOMP_LOG_KILL_THREAD, SECCOMP_RET_KILL_THREAD_NAME },
 	{ SECCOMP_LOG_TRAP, SECCOMP_RET_TRAP_NAME },
 	{ SECCOMP_LOG_ERRNO, SECCOMP_RET_ERRNO_NAME },
+	{ SECCOMP_LOG_USER_NOTIF, SECCOMP_RET_USER_NOTIF_NAME },
 	{ SECCOMP_LOG_TRACE, SECCOMP_RET_TRACE_NAME },
 	{ SECCOMP_LOG_LOG, SECCOMP_RET_LOG_NAME },
 	{ SECCOMP_LOG_ALLOW, SECCOMP_RET_ALLOW_NAME },