--- zzzz-none-000/linux-5.4.213/fs/notify/fanotify/fanotify.h	2022-09-15 10:04:56.000000000 +0000
+++ alder-5690pro-762/linux-5.4.213/fs/notify/fanotify/fanotify.h	2024-08-14 09:02:08.000000000 +0000
@@ -5,7 +5,8 @@
 #include <linux/exportfs.h>
 
 extern struct kmem_cache *fanotify_mark_cache;
-extern struct kmem_cache *fanotify_event_cachep;
+extern struct kmem_cache *fanotify_fid_event_cachep;
+extern struct kmem_cache *fanotify_path_event_cachep;
 extern struct kmem_cache *fanotify_perm_event_cachep;
 
 /* Possible states of the permission event */
@@ -18,94 +19,222 @@
 
 /*
  * 3 dwords are sufficient for most local fs (64bit ino, 32bit generation).
- * For 32bit arch, fid increases the size of fanotify_event by 12 bytes and
- * fh_* fields increase the size of fanotify_event by another 4 bytes.
- * For 64bit arch, fid increases the size of fanotify_fid by 8 bytes and
- * fh_* fields are packed in a hole after mask.
+ * fh buf should be dword aligned. On 64bit arch, the ext_buf pointer is
+ * stored in either the first or last 2 dwords.
  */
-#if BITS_PER_LONG == 32
 #define FANOTIFY_INLINE_FH_LEN	(3 << 2)
-#else
-#define FANOTIFY_INLINE_FH_LEN	(4 << 2)
-#endif
+#define FANOTIFY_FH_HDR_LEN	offsetof(struct fanotify_fh, buf)
 
-struct fanotify_fid {
-	__kernel_fsid_t fsid;
-	union {
-		unsigned char fh[FANOTIFY_INLINE_FH_LEN];
-		unsigned char *ext_fh;
-	};
-};
+/* Fixed size struct for file handle */
+struct fanotify_fh {
+	u8 type;
+	u8 len;
+#define FANOTIFY_FH_FLAG_EXT_BUF 1
+	u8 flags;
+	u8 pad;
+	unsigned char buf[];
+} __aligned(4);
+
+/* Variable size struct for dir file handle + child file handle + name */
+struct fanotify_info {
+	/* size of dir_fh/file_fh including fanotify_fh hdr size */
+	u8 dir_fh_totlen;
+	u8 file_fh_totlen;
+	u8 name_len;
+	u8 pad;
+	unsigned char buf[];
+	/*
+	 * (struct fanotify_fh) dir_fh starts at buf[0]
+	 * (optional) file_fh starts at buf[dir_fh_totlen]
+	 * name starts at buf[dir_fh_totlen + file_fh_totlen]
+	 */
+} __aligned(4);
+
+static inline bool fanotify_fh_has_ext_buf(struct fanotify_fh *fh)
+{
+	return (fh->flags & FANOTIFY_FH_FLAG_EXT_BUF);
+}
+
+static inline char **fanotify_fh_ext_buf_ptr(struct fanotify_fh *fh)
+{
+	BUILD_BUG_ON(FANOTIFY_FH_HDR_LEN % 4);
+	BUILD_BUG_ON(__alignof__(char *) - 4 + sizeof(char *) >
+		     FANOTIFY_INLINE_FH_LEN);
+	return (char **)ALIGN((unsigned long)(fh->buf), __alignof__(char *));
+}
 
-static inline void *fanotify_fid_fh(struct fanotify_fid *fid,
-				    unsigned int fh_len)
+static inline void *fanotify_fh_ext_buf(struct fanotify_fh *fh)
 {
-	return fh_len <= FANOTIFY_INLINE_FH_LEN ? fid->fh : fid->ext_fh;
+	return *fanotify_fh_ext_buf_ptr(fh);
 }
 
-static inline bool fanotify_fid_equal(struct fanotify_fid *fid1,
-				      struct fanotify_fid *fid2,
-				      unsigned int fh_len)
+static inline void *fanotify_fh_buf(struct fanotify_fh *fh)
 {
-	return fid1->fsid.val[0] == fid2->fsid.val[0] &&
-		fid1->fsid.val[1] == fid2->fsid.val[1] &&
-		!memcmp(fanotify_fid_fh(fid1, fh_len),
-			fanotify_fid_fh(fid2, fh_len), fh_len);
+	return fanotify_fh_has_ext_buf(fh) ? fanotify_fh_ext_buf(fh) : fh->buf;
+}
+
+static inline int fanotify_info_dir_fh_len(struct fanotify_info *info)
+{
+	if (!info->dir_fh_totlen ||
+	    WARN_ON_ONCE(info->dir_fh_totlen < FANOTIFY_FH_HDR_LEN))
+		return 0;
+
+	return info->dir_fh_totlen - FANOTIFY_FH_HDR_LEN;
+}
+
+static inline struct fanotify_fh *fanotify_info_dir_fh(struct fanotify_info *info)
+{
+	BUILD_BUG_ON(offsetof(struct fanotify_info, buf) % 4);
+
+	return (struct fanotify_fh *)info->buf;
+}
+
+static inline int fanotify_info_file_fh_len(struct fanotify_info *info)
+{
+	if (!info->file_fh_totlen ||
+	    WARN_ON_ONCE(info->file_fh_totlen < FANOTIFY_FH_HDR_LEN))
+		return 0;
+
+	return info->file_fh_totlen - FANOTIFY_FH_HDR_LEN;
+}
+
+static inline struct fanotify_fh *fanotify_info_file_fh(struct fanotify_info *info)
+{
+	return (struct fanotify_fh *)(info->buf + info->dir_fh_totlen);
+}
+
+static inline const char *fanotify_info_name(struct fanotify_info *info)
+{
+	return info->buf + info->dir_fh_totlen + info->file_fh_totlen;
+}
+
+static inline void fanotify_info_init(struct fanotify_info *info)
+{
+	info->dir_fh_totlen = 0;
+	info->file_fh_totlen = 0;
+	info->name_len = 0;
+}
+
+static inline void fanotify_info_copy_name(struct fanotify_info *info,
+					   const struct qstr *name)
+{
+	info->name_len = name->len;
+	strcpy(info->buf + info->dir_fh_totlen + info->file_fh_totlen,
+	       name->name);
 }
 
 /*
- * Structure for normal fanotify events. It gets allocated in
+ * Common structure for fanotify events. Concrete structs are allocated in
  * fanotify_handle_event() and freed when the information is retrieved by
- * userspace
+ * userspace. The type of event determines how it was allocated, how it will
+ * be freed and which concrete struct it may be cast to.
  */
+enum fanotify_event_type {
+	FANOTIFY_EVENT_TYPE_FID, /* fixed length */
+	FANOTIFY_EVENT_TYPE_FID_NAME, /* variable length */
+	FANOTIFY_EVENT_TYPE_PATH,
+	FANOTIFY_EVENT_TYPE_PATH_PERM,
+	FANOTIFY_EVENT_TYPE_OVERFLOW, /* struct fanotify_event */
+};
+
 struct fanotify_event {
 	struct fsnotify_event fse;
 	u32 mask;
-	/*
-	 * Those fields are outside fanotify_fid to pack fanotify_event nicely
-	 * on 64bit arch and to use fh_type as an indication of whether path
-	 * or fid are used in the union:
-	 * FILEID_ROOT (0) for path, > 0 for fid, FILEID_INVALID for neither.
-	 */
-	u8 fh_type;
-	u8 fh_len;
-	u16 pad;
-	union {
-		/*
-		 * We hold ref to this path so it may be dereferenced at any
-		 * point during this object's lifetime
-		 */
-		struct path path;
-		/*
-		 * With FAN_REPORT_FID, we do not hold any reference on the
-		 * victim object. Instead we store its NFS file handle and its
-		 * filesystem's fsid as a unique identifier.
-		 */
-		struct fanotify_fid fid;
-	};
+	enum fanotify_event_type type;
 	struct pid *pid;
 };
 
-static inline bool fanotify_event_has_path(struct fanotify_event *event)
+static inline void fanotify_init_event(struct fanotify_event *event,
+				       unsigned long id, u32 mask)
+{
+	fsnotify_init_event(&event->fse, id);
+	event->mask = mask;
+	event->pid = NULL;
+}
+
+struct fanotify_fid_event {
+	struct fanotify_event fae;
+	__kernel_fsid_t fsid;
+	struct fanotify_fh object_fh;
+	/* Reserve space in object_fh.buf[] - access with fanotify_fh_buf() */
+	unsigned char _inline_fh_buf[FANOTIFY_INLINE_FH_LEN];
+};
+
+static inline struct fanotify_fid_event *
+FANOTIFY_FE(struct fanotify_event *event)
+{
+	return container_of(event, struct fanotify_fid_event, fae);
+}
+
+struct fanotify_name_event {
+	struct fanotify_event fae;
+	__kernel_fsid_t fsid;
+	struct fanotify_info info;
+};
+
+static inline struct fanotify_name_event *
+FANOTIFY_NE(struct fanotify_event *event)
+{
+	return container_of(event, struct fanotify_name_event, fae);
+}
+
+static inline __kernel_fsid_t *fanotify_event_fsid(struct fanotify_event *event)
 {
-	return event->fh_type == FILEID_ROOT;
+	if (event->type == FANOTIFY_EVENT_TYPE_FID)
+		return &FANOTIFY_FE(event)->fsid;
+	else if (event->type == FANOTIFY_EVENT_TYPE_FID_NAME)
+		return &FANOTIFY_NE(event)->fsid;
+	else
+		return NULL;
 }
 
-static inline bool fanotify_event_has_fid(struct fanotify_event *event)
+static inline struct fanotify_fh *fanotify_event_object_fh(
+						struct fanotify_event *event)
 {
-	return event->fh_type != FILEID_ROOT &&
-		event->fh_type != FILEID_INVALID;
+	if (event->type == FANOTIFY_EVENT_TYPE_FID)
+		return &FANOTIFY_FE(event)->object_fh;
+	else if (event->type == FANOTIFY_EVENT_TYPE_FID_NAME)
+		return fanotify_info_file_fh(&FANOTIFY_NE(event)->info);
+	else
+		return NULL;
 }
 
-static inline bool fanotify_event_has_ext_fh(struct fanotify_event *event)
+static inline struct fanotify_info *fanotify_event_info(
+						struct fanotify_event *event)
 {
-	return fanotify_event_has_fid(event) &&
-		event->fh_len > FANOTIFY_INLINE_FH_LEN;
+	if (event->type == FANOTIFY_EVENT_TYPE_FID_NAME)
+		return &FANOTIFY_NE(event)->info;
+	else
+		return NULL;
+}
+
+static inline int fanotify_event_object_fh_len(struct fanotify_event *event)
+{
+	struct fanotify_info *info = fanotify_event_info(event);
+	struct fanotify_fh *fh = fanotify_event_object_fh(event);
+
+	if (info)
+		return info->file_fh_totlen ? fh->len : 0;
+	else
+		return fh ? fh->len : 0;
+}
+
+static inline int fanotify_event_dir_fh_len(struct fanotify_event *event)
+{
+	struct fanotify_info *info = fanotify_event_info(event);
+
+	return info ? fanotify_info_dir_fh_len(info) : 0;
 }
 
-static inline void *fanotify_event_fh(struct fanotify_event *event)
+struct fanotify_path_event {
+	struct fanotify_event fae;
+	struct path path;
+};
+
+static inline struct fanotify_path_event *
+FANOTIFY_PE(struct fanotify_event *event)
 {
-	return fanotify_fid_fh(&event->fid, event->fh_len);
+	return container_of(event, struct fanotify_path_event, fae);
 }
 
 /*
@@ -117,15 +246,16 @@
  */
 struct fanotify_perm_event {
 	struct fanotify_event fae;
+	struct path path;
 	unsigned short response;	/* userspace answer to the event */
 	unsigned short state;		/* state of the event */
 	int fd;		/* fd we passed to userspace for this event */
 };
 
 static inline struct fanotify_perm_event *
-FANOTIFY_PE(struct fsnotify_event *fse)
+FANOTIFY_PERM(struct fanotify_event *event)
 {
-	return container_of(fse, struct fanotify_perm_event, fae.fse);
+	return container_of(event, struct fanotify_perm_event, fae);
 }
 
 static inline bool fanotify_is_perm_event(u32 mask)
@@ -139,7 +269,18 @@
 	return container_of(fse, struct fanotify_event, fse);
 }
 
-struct fanotify_event *fanotify_alloc_event(struct fsnotify_group *group,
-					    struct inode *inode, u32 mask,
-					    const void *data, int data_type,
-					    __kernel_fsid_t *fsid);
+static inline bool fanotify_event_has_path(struct fanotify_event *event)
+{
+	return event->type == FANOTIFY_EVENT_TYPE_PATH ||
+		event->type == FANOTIFY_EVENT_TYPE_PATH_PERM;
+}
+
+static inline struct path *fanotify_event_path(struct fanotify_event *event)
+{
+	if (event->type == FANOTIFY_EVENT_TYPE_PATH)
+		return &FANOTIFY_PE(event)->path;
+	else if (event->type == FANOTIFY_EVENT_TYPE_PATH_PERM)
+		return &FANOTIFY_PERM(event)->path;
+	else
+		return NULL;
+}