1 files changed, 296 insertions, 0 deletions
diff --git a/fs/notify/fanotify/fanotify.c b/fs/notify/fanotify/fanotify.c
new file mode 100644
index 000000000..ca3405f73
--- /dev/null
+++ b/fs/notify/fanotify/fanotify.c
@@ -0,0 +1,296 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/fanotify.h>
+#include <linux/fdtable.h>
+#include <linux/fsnotify_backend.h>
+#include <linux/init.h>
+#include <linux/jiffies.h>
+#include <linux/kernel.h> /* UINT_MAX */
+#include <linux/mount.h>
+#include <linux/sched.h>
+#include <linux/sched/user.h>
+#include <linux/sched/signal.h>
+#include <linux/types.h>
+#include <linux/wait.h>
+#include <linux/audit.h>
+#include <linux/sched/mm.h>
+
+#include "fanotify.h"
+
+static bool should_merge(struct fsnotify_event *old_fsn,
+			 struct fsnotify_event *new_fsn)
+{
+	struct fanotify_event_info *old, *new;
+
+	pr_debug("%s: old=%p new=%p\n", __func__, old_fsn, new_fsn);
+	old = FANOTIFY_E(old_fsn);
+	new = FANOTIFY_E(new_fsn);
+
+	if (old_fsn->inode == new_fsn->inode && old->tgid == new->tgid &&
+	    old->path.mnt == new->path.mnt &&
+	    old->path.dentry == new->path.dentry)
+		return true;
+	return false;
+}
+
+/* and the list better be locked by something too! */
+static int fanotify_merge(struct list_head *list, struct fsnotify_event *event)
+{
+	struct fsnotify_event *test_event;
+
+	pr_debug("%s: list=%p event=%p\n", __func__, list, event);
+
+	/*
+	 * Don't merge a permission event with any other event so that we know
+	 * the event structure we have created in fanotify_handle_event() is the
+	 * one we should check for permission response.
+	 */
+	if (fanotify_is_perm_event(event->mask))
+		return 0;
+
+	list_for_each_entry_reverse(test_event, list, list) {
+		if (should_merge(test_event, event)) {
+			test_event->mask |= event->mask;
+			return 1;
+		}
+	}
+
+	return 0;
+}
+
+static int fanotify_get_response(struct fsnotify_group *group,
+				 struct fanotify_perm_event_info *event,
+				 struct fsnotify_iter_info *iter_info)
+{
+	int ret;
+
+	pr_debug("%s: group=%p event=%p\n", __func__, group, event);
+
+	wait_event(group->fanotify_data.access_waitq, event->response);
+
+	/* userspace responded, convert to something usable */
+	switch (event->response & ~FAN_AUDIT) {
+	case FAN_ALLOW:
+		ret = 0;
+		break;
+	case FAN_DENY:
+	default:
+		ret = -EPERM;
+	}
+
+	/* Check if the response should be audited */
+	if (event->response & FAN_AUDIT)
+		audit_fanotify(event->response & ~FAN_AUDIT);
+
+	event->response = 0;
+
+	pr_debug("%s: group=%p event=%p about to return ret=%d\n", __func__,
+		 group, event, ret);
+	
+	return ret;
+}
+
+static bool fanotify_should_send_event(struct fsnotify_iter_info *iter_info,
+				       u32 event_mask, const void *data,
+				       int data_type)
+{
+	__u32 marks_mask = 0, marks_ignored_mask = 0;
+	const struct path *path = data;
+	struct fsnotify_mark *mark;
+	int type;
+
+	pr_debug("%s: report_mask=%x mask=%x data=%p data_type=%d\n",
+		 __func__, iter_info->report_mask, event_mask, data, data_type);
+
+	/* if we don't have enough info to send an event to userspace say no */
+	if (data_type != FSNOTIFY_EVENT_PATH)
+		return false;
+
+	/* sorry, fanotify only gives a damn about files and dirs */
+	if (!d_is_reg(path->dentry) &&
+	    !d_can_lookup(path->dentry))
+		return false;
+
+	fsnotify_foreach_obj_type(type) {
+		if (!fsnotify_iter_should_report_type(iter_info, type))
+			continue;
+		mark = iter_info->marks[type];
+
+		/* Apply ignore mask regardless of ISDIR and ON_CHILD flags */
+		marks_ignored_mask |= mark->ignored_mask;
+
+		/*
+		 * If the event is for a child and this mark doesn't care about
+		 * events on a child, don't send it!
+		 */
+		if (event_mask & FS_EVENT_ON_CHILD &&
+		    (type != FSNOTIFY_OBJ_TYPE_INODE ||
+		     !(mark->mask & FS_EVENT_ON_CHILD)))
+			continue;
+
+		marks_mask |= mark->mask;
+	}
+
+	if (d_is_dir(path->dentry) &&
+	    !(marks_mask & FS_ISDIR & ~marks_ignored_mask))
+		return false;
+
+	if (event_mask & FAN_ALL_OUTGOING_EVENTS & marks_mask &
+				 ~marks_ignored_mask)
+		return true;
+
+	return false;
+}
+
+struct fanotify_event_info *fanotify_alloc_event(struct fsnotify_group *group,
+						 struct inode *inode, u32 mask,
+						 const struct path *path)
+{
+	struct fanotify_event_info *event = NULL;
+	gfp_t gfp = GFP_KERNEL_ACCOUNT;
+
+	/*
+	 * For queues with unlimited length lost events are not expected and
+	 * can possibly have security implications. Avoid losing events when
+	 * memory is short. For the limited size queues, avoid OOM killer in the
+	 * target monitoring memcg as it may have security repercussion.
+	 */
+	if (group->max_events == UINT_MAX)
+		gfp |= __GFP_NOFAIL;
+	else
+		gfp |= __GFP_RETRY_MAYFAIL;
+
+	/* Whoever is interested in the event, pays for the allocation. */
+	memalloc_use_memcg(group->memcg);
+
+	if (fanotify_is_perm_event(mask)) {
+		struct fanotify_perm_event_info *pevent;
+
+		pevent = kmem_cache_alloc(fanotify_perm_event_cachep, gfp);
+		if (!pevent)
+			goto out;
+		event = &pevent->fae;
+		pevent->response = 0;
+		goto init;
+	}
+	event = kmem_cache_alloc(fanotify_event_cachep, gfp);
+	if (!event)
+		goto out;
+init: __maybe_unused
+	fsnotify_init_event(&event->fse, inode, mask);
+	event->tgid = get_pid(task_tgid(current));
+	if (path) {
+		event->path = *path;
+		path_get(&event->path);
+	} else {
+		event->path.mnt = NULL;
+		event->path.dentry = NULL;
+	}
+out:
+	memalloc_unuse_memcg();
+	return event;
+}
+
+static int fanotify_handle_event(struct fsnotify_group *group,
+				 struct inode *inode,
+				 u32 mask, const void *data, int data_type,
+				 const unsigned char *file_name, u32 cookie,
+				 struct fsnotify_iter_info *iter_info)
+{
+	int ret = 0;
+	struct fanotify_event_info *event;
+	struct fsnotify_event *fsn_event;
+
+	BUILD_BUG_ON(FAN_ACCESS != FS_ACCESS);
+	BUILD_BUG_ON(FAN_MODIFY != FS_MODIFY);
+	BUILD_BUG_ON(FAN_CLOSE_NOWRITE != FS_CLOSE_NOWRITE);
+	BUILD_BUG_ON(FAN_CLOSE_WRITE != FS_CLOSE_WRITE);
+	BUILD_BUG_ON(FAN_OPEN != FS_OPEN);
+	BUILD_BUG_ON(FAN_EVENT_ON_CHILD != FS_EVENT_ON_CHILD);
+	BUILD_BUG_ON(FAN_Q_OVERFLOW != FS_Q_OVERFLOW);
+	BUILD_BUG_ON(FAN_OPEN_PERM != FS_OPEN_PERM);
+	BUILD_BUG_ON(FAN_ACCESS_PERM != FS_ACCESS_PERM);
+	BUILD_BUG_ON(FAN_ONDIR != FS_ISDIR);
+
+	if (!fanotify_should_send_event(iter_info, mask, data, data_type))
+		return 0;
+
+	pr_debug("%s: group=%p inode=%p mask=%x\n", __func__, group, inode,
+		 mask);
+
+	if (fanotify_is_perm_event(mask)) {
+		/*
+		 * fsnotify_prepare_user_wait() fails if we race with mark
+		 * deletion.  Just let the operation pass in that case.
+		 */
+		if (!fsnotify_prepare_user_wait(iter_info))
+			return 0;
+	}
+
+	event = fanotify_alloc_event(group, inode, mask, data);
+	ret = -ENOMEM;
+	if (unlikely(!event)) {
+		/*
+		 * We don't queue overflow events for permission events as
+		 * there the access is denied and so no event is in fact lost.
+		 */
+		if (!fanotify_is_perm_event(mask))
+			fsnotify_queue_overflow(group);
+		goto finish;
+	}
+
+	fsn_event = &event->fse;
+	ret = fsnotify_add_event(group, fsn_event, fanotify_merge);
+	if (ret) {
+		/* Permission events shouldn't be merged */
+		BUG_ON(ret == 1 && mask & FAN_ALL_PERM_EVENTS);
+		/* Our event wasn't used in the end. Free it. */
+		fsnotify_destroy_event(group, fsn_event);
+
+		ret = 0;
+	} else if (fanotify_is_perm_event(mask)) {
+		ret = fanotify_get_response(group, FANOTIFY_PE(fsn_event),
+					    iter_info);
+		fsnotify_destroy_event(group, fsn_event);
+	}
+finish:
+	if (fanotify_is_perm_event(mask))
+		fsnotify_finish_user_wait(iter_info);
+
+	return ret;
+}
+
+static void fanotify_free_group_priv(struct fsnotify_group *group)
+{
+	struct user_struct *user;
+
+	user = group->fanotify_data.user;
+	atomic_dec(&user->fanotify_listeners);
+	free_uid(user);
+}
+
+static void fanotify_free_event(struct fsnotify_event *fsn_event)
+{
+	struct fanotify_event_info *event;
+
+	event = FANOTIFY_E(fsn_event);
+	path_put(&event->path);
+	put_pid(event->tgid);
+	if (fanotify_is_perm_event(fsn_event->mask)) {
+		kmem_cache_free(fanotify_perm_event_cachep,
+				FANOTIFY_PE(fsn_event));
+		return;
+	}
+	kmem_cache_free(fanotify_event_cachep, event);
+}
+
+static void fanotify_free_mark(struct fsnotify_mark *fsn_mark)
+{
+	kmem_cache_free(fanotify_mark_cache, fsn_mark);
+}
+
+const struct fsnotify_ops fanotify_fsnotify_ops = {
+	.handle_event = fanotify_handle_event,
+	.free_group_priv = fanotify_free_group_priv,
+	.free_event = fanotify_free_event,
+	.free_mark = fanotify_free_mark,
+};