fanotify: deprecate uapi FAN_ALL_* constants

We do not want to add new bits to the FAN_ALL_* uapi constants
because they have been exposed to userspace.  If there are programs
out there using these constants, those programs could break if
re-compiled with modified FAN_ALL_* constants and run on an old kernel.

We deprecate the uapi constants FAN_ALL_* and define new FANOTIFY_*
constants for internal use to replace them. New feature bits will be
added only to the new constants.

Cc: <linux-api@vger.kernel.org>
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>

fs/notify/fanotify/fanotify.c

@@ -131,8 +131,8 @@ static bool fanotify_should_send_event(struct fsnotify_iter_info *iter_info,
 	    !(marks_mask & FS_ISDIR & ~marks_ignored_mask))
 		return false;
 
-	if (event_mask & FAN_ALL_OUTGOING_EVENTS & marks_mask &
-				 ~marks_ignored_mask)
+	if (event_mask & FANOTIFY_OUTGOING_EVENTS &
+	    marks_mask & ~marks_ignored_mask)
 		return true;
 
 	return false;
@@ -236,7 +236,7 @@ static int fanotify_handle_event(struct fsnotify_group *group,
 	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);
+		BUG_ON(ret == 1 && mask & FANOTIFY_PERM_EVENTS);
 		/* Our event wasn't used in the end. Free it. */
 		fsnotify_destroy_event(group, fsn_event);
 

fs/notify/fanotify/fanotify.h

@@ -44,7 +44,7 @@ FANOTIFY_PE(struct fsnotify_event *fse)
 static inline bool fanotify_is_perm_event(u32 mask)
 {
 	return IS_ENABLED(CONFIG_FANOTIFY_ACCESS_PERMISSIONS) &&
-		mask & FAN_ALL_PERM_EVENTS;
+		mask & FANOTIFY_PERM_EVENTS;
 }
 
 static inline struct fanotify_event_info *FANOTIFY_E(struct fsnotify_event *fse)

fs/notify/fanotify/fanotify_user.c

@@ -131,7 +131,7 @@ static int fill_event_metadata(struct fsnotify_group *group,
 	metadata->metadata_len = FAN_EVENT_METADATA_LEN;
 	metadata->vers = FANOTIFY_METADATA_VERSION;
 	metadata->reserved = 0;
-	metadata->mask = fsn_event->mask & FAN_ALL_OUTGOING_EVENTS;
+	metadata->mask = fsn_event->mask & FANOTIFY_OUTGOING_EVENTS;
 	metadata->pid = pid_vnr(event->tgid);
 	if (unlikely(fsn_event->mask & FAN_Q_OVERFLOW))
 		metadata->fd = FAN_NOFD;
@@ -395,7 +395,7 @@ static int fanotify_release(struct inode *ignored, struct file *file)
 	 */
 	while (!fsnotify_notify_queue_is_empty(group)) {
 		fsn_event = fsnotify_remove_first_event(group);
-		if (!(fsn_event->mask & FAN_ALL_PERM_EVENTS)) {
+		if (!(fsn_event->mask & FANOTIFY_PERM_EVENTS)) {
 			spin_unlock(&group->notification_lock);
 			fsnotify_destroy_event(group, fsn_event);
 			spin_lock(&group->notification_lock);
@@ -691,9 +691,9 @@ SYSCALL_DEFINE2(fanotify_init, unsigned int, flags, unsigned int, event_f_flags)
 		return -EPERM;
 
 #ifdef CONFIG_AUDITSYSCALL
-	if (flags & ~(FAN_ALL_INIT_FLAGS | FAN_ENABLE_AUDIT))
+	if (flags & ~(FANOTIFY_INIT_FLAGS | FAN_ENABLE_AUDIT))
 #else
-	if (flags & ~FAN_ALL_INIT_FLAGS)
+	if (flags & ~FANOTIFY_INIT_FLAGS)
 #endif
 		return -EINVAL;
 
@@ -745,7 +745,7 @@ SYSCALL_DEFINE2(fanotify_init, unsigned int, flags, unsigned int, event_f_flags)
 	group->fanotify_data.f_flags = event_f_flags;
 	init_waitqueue_head(&group->fanotify_data.access_waitq);
 	INIT_LIST_HEAD(&group->fanotify_data.access_list);
-	switch (flags & FAN_ALL_CLASS_BITS) {
+	switch (flags & FANOTIFY_CLASS_BITS) {
 	case FAN_CLASS_NOTIF:
 		group->priority = FS_PRIO_0;
 		break;
@@ -803,8 +803,8 @@ static int do_fanotify_mark(int fanotify_fd, unsigned int flags, __u64 mask,
 	struct fsnotify_group *group;
 	struct fd f;
 	struct path path;
-	u32 valid_mask = FAN_ALL_EVENTS | FAN_EVENT_ON_CHILD | FAN_ONDIR;
-	unsigned int mark_type = flags & FAN_MARK_TYPE_MASK;
+	u32 valid_mask = FANOTIFY_EVENTS | FAN_EVENT_ON_CHILD | FAN_ONDIR;
+	unsigned int mark_type = flags & FANOTIFY_MARK_TYPE_BITS;
 	int ret;
 
 	pr_debug("%s: fanotify_fd=%d flags=%x dfd=%d pathname=%p mask=%llx\n",
@@ -814,7 +814,7 @@ static int do_fanotify_mark(int fanotify_fd, unsigned int flags, __u64 mask,
 	if (mask & ((__u64)0xffffffff << 32))
 		return -EINVAL;
 
-	if (flags & ~FAN_ALL_MARK_FLAGS)
+	if (flags & ~FANOTIFY_MARK_FLAGS)
 		return -EINVAL;
 
 	switch (mark_type) {
@@ -833,15 +833,15 @@ static int do_fanotify_mark(int fanotify_fd, unsigned int flags, __u64 mask,
 			return -EINVAL;
 		break;
 	case FAN_MARK_FLUSH:
-		if (flags & ~(FAN_MARK_TYPE_MASK | FAN_MARK_FLUSH))
+		if (flags & ~(FANOTIFY_MARK_TYPE_BITS | FAN_MARK_FLUSH))
 			return -EINVAL;
 		break;
 	default:
 		return -EINVAL;
 	}
 
 	if (IS_ENABLED(CONFIG_FANOTIFY_ACCESS_PERMISSIONS))
-		valid_mask |= FAN_ALL_PERM_EVENTS;
+		valid_mask |= FANOTIFY_PERM_EVENTS;
 
 	if (mask & ~valid_mask)
 		return -EINVAL;
@@ -861,7 +861,7 @@ static int do_fanotify_mark(int fanotify_fd, unsigned int flags, __u64 mask,
 	 * allowed to set permissions events.
 	 */
 	ret = -EINVAL;
-	if (mask & FAN_ALL_PERM_EVENTS &&
+	if (mask & FANOTIFY_PERM_EVENTS &&
 	    group->priority == FS_PRIO_0)
 		goto fput_and_out;
 

include/linux/fanotify.h

@@ -7,4 +7,51 @@
 #define FAN_GROUP_FLAG(group, flag) \
 	((group)->fanotify_data.flags & (flag))
 
+/*
+ * Flags allowed to be passed from/to userspace.
+ *
+ * We intentionally do not add new bits to the old FAN_ALL_* constants, because
+ * they are uapi exposed constants. If there are programs out there using
+ * these constant, the programs may break if re-compiled with new uapi headers
+ * and then run on an old kernel.
+ */
+#define FANOTIFY_CLASS_BITS	(FAN_CLASS_NOTIF | FAN_CLASS_CONTENT | \
+				 FAN_CLASS_PRE_CONTENT)
+
+#define FANOTIFY_INIT_FLAGS	(FANOTIFY_CLASS_BITS | \
+				 FAN_CLOEXEC | FAN_NONBLOCK | \
+				 FAN_UNLIMITED_QUEUE | FAN_UNLIMITED_MARKS)
+
+#define FANOTIFY_MARK_TYPE_BITS	(FAN_MARK_INODE | FAN_MARK_MOUNT | \
+				 FAN_MARK_FILESYSTEM)
+
+#define FANOTIFY_MARK_FLAGS	(FANOTIFY_MARK_TYPE_BITS | \
+				 FAN_MARK_ADD | \
+				 FAN_MARK_REMOVE | \
+				 FAN_MARK_DONT_FOLLOW | \
+				 FAN_MARK_ONLYDIR | \
+				 FAN_MARK_IGNORED_MASK | \
+				 FAN_MARK_IGNORED_SURV_MODIFY | \
+				 FAN_MARK_FLUSH)
+
+/* Events that user can request to be notified on */
+#define FANOTIFY_EVENTS		(FAN_ACCESS | FAN_MODIFY | \
+				 FAN_CLOSE | FAN_OPEN)
+
+/* Events that require a permission response from user */
+#define FANOTIFY_PERM_EVENTS	(FAN_OPEN_PERM | FAN_ACCESS_PERM)
+
+/* Events that may be reported to user */
+#define FANOTIFY_OUTGOING_EVENTS	(FANOTIFY_EVENTS | \
+					 FANOTIFY_PERM_EVENTS | \
+					 FAN_Q_OVERFLOW)
+
+/* Do not use these old uapi constants internally */
+#undef FAN_ALL_CLASS_BITS
+#undef FAN_ALL_INIT_FLAGS
+#undef FAN_ALL_MARK_FLAGS
+#undef FAN_ALL_EVENTS
+#undef FAN_ALL_PERM_EVENTS
+#undef FAN_ALL_OUTGOING_EVENTS
+
 #endif /* _LINUX_FANOTIFY_H */

include/uapi/linux/fanotify.h

@@ -31,13 +31,16 @@
 #define FAN_CLASS_NOTIF		0x00000000
 #define FAN_CLASS_CONTENT	0x00000004
 #define FAN_CLASS_PRE_CONTENT	0x00000008
+
+/* Deprecated - do not use this in programs and do not add new flags here! */
 #define FAN_ALL_CLASS_BITS	(FAN_CLASS_NOTIF | FAN_CLASS_CONTENT | \
 				 FAN_CLASS_PRE_CONTENT)
 
 #define FAN_UNLIMITED_QUEUE	0x00000010
 #define FAN_UNLIMITED_MARKS	0x00000020
 #define FAN_ENABLE_AUDIT	0x00000040
 
+/* Deprecated - do not use this in programs and do not add new flags here! */
 #define FAN_ALL_INIT_FLAGS	(FAN_CLOEXEC | FAN_NONBLOCK | \
 				 FAN_ALL_CLASS_BITS | FAN_UNLIMITED_QUEUE |\
 				 FAN_UNLIMITED_MARKS)
@@ -57,23 +60,18 @@
 #define FAN_MARK_INODE		0x00000000
 #define FAN_MARK_MOUNT		0x00000010
 #define FAN_MARK_FILESYSTEM	0x00000100
-#define FAN_MARK_TYPE_MASK	(FAN_MARK_INODE | FAN_MARK_MOUNT | \
-				 FAN_MARK_FILESYSTEM)
 
+/* Deprecated - do not use this in programs and do not add new flags here! */
 #define FAN_ALL_MARK_FLAGS	(FAN_MARK_ADD |\
 				 FAN_MARK_REMOVE |\
 				 FAN_MARK_DONT_FOLLOW |\
 				 FAN_MARK_ONLYDIR |\
+				 FAN_MARK_MOUNT |\
 				 FAN_MARK_IGNORED_MASK |\
 				 FAN_MARK_IGNORED_SURV_MODIFY |\
-				 FAN_MARK_FLUSH|\
-				 FAN_MARK_TYPE_MASK)
+				 FAN_MARK_FLUSH)
 
-/*
- * All of the events - we build the list by hand so that we can add flags in
- * the future and not break backward compatibility.  Apps will get only the
- * events that they originally wanted.  Be sure to add new events here!
- */
+/* Deprecated - do not use this in programs and do not add new flags here! */
 #define FAN_ALL_EVENTS (FAN_ACCESS |\
 			FAN_MODIFY |\
 			FAN_CLOSE |\
@@ -82,9 +80,11 @@
 /*
  * All events which require a permission response from userspace
  */
+/* Deprecated - do not use this in programs and do not add new flags here! */
 #define FAN_ALL_PERM_EVENTS (FAN_OPEN_PERM |\
 			     FAN_ACCESS_PERM)
 
+/* Deprecated - do not use this in programs and do not add new flags here! */
 #define FAN_ALL_OUTGOING_EVENTS	(FAN_ALL_EVENTS |\
 				 FAN_ALL_PERM_EVENTS |\
 				 FAN_Q_OVERFLOW)