Commit 0aca67bb authored by Matthew Bobrowski's avatar Matthew Bobrowski Committed by Jan Kara
Browse files

fanotify: introduce a generic info record copying helper 

The copy_info_records_to_user() helper allows for the separation of
info record copying routines/conditionals from copy_event_to_user(),
which reduces the overall clutter within this function. This becomes
especially true as we start introducing additional info records in the
future i.e. struct fanotify_event_info_pidfd. On success, this helper
returns the total amount of bytes that have been copied into the user
supplied buffer and on error, a negative value is returned to the
caller.

The newly defined macro FANOTIFY_INFO_MODES can be used to obtain info
record types that have been enabled for a specific notification
group. This macro becomes useful in the subsequent patch when the
FAN_REPORT_PIDFD initialization flag is introduced.

Link: https://lore.kernel.org/r/8872947dfe12ce8ae6e9a7f2d49ea29bc8006af0.1628398044.git.repnop@google.com


Signed-off-by: default avatarMatthew Bobrowski <repnop@google.com>
Reviewed-by: default avatarAmir Goldstein <amir73il@gmail.com>
Signed-off-by: default avatarJan Kara <jack@suse.cz>
parent d3424c9b

fs/notify/fanotify/fanotify_user.c

+88 −67
Original line number Diff line number Diff line
@@ -173,7 +173,7 @@ static struct fanotify_event *get_one_event(struct fsnotify_group *group, 
	size_t event_size = FAN_EVENT_METADATA_LEN;

	struct fanotify_event *event = NULL;

	struct fsnotify_event *fsn_event;

	unsigned int fid_mode = FAN_GROUP_FLAG(group, FANOTIFY_FID_BITS);

	unsigned int info_mode = FAN_GROUP_FLAG(group, FANOTIFY_INFO_MODES);



	pr_debug("%s: group=%p count=%zd\n", __func__, group, count);
@@ -183,8 +183,8 @@ static struct fanotify_event *get_one_event(struct fsnotify_group *group, 
		goto out;



	event = FANOTIFY_E(fsn_event);

	if (fid_mode)

		event_size += fanotify_event_info_len(fid_mode, event);

	if (info_mode)

		event_size += fanotify_event_info_len(info_mode, event);



	if (event_size > count) {

		event = ERR_PTR(-EINVAL);
@@ -401,6 +401,86 @@ static int copy_fid_info_to_user(__kernel_fsid_t *fsid, struct fanotify_fh *fh, 
	return info_len;

}



static int copy_info_records_to_user(struct fanotify_event *event,

				     struct fanotify_info *info,

				     unsigned int info_mode,

				     char __user *buf, size_t count)

{

	int ret, total_bytes = 0, info_type = 0;

	unsigned int fid_mode = info_mode & FANOTIFY_FID_BITS;



	/*

	 * Event info records order is as follows: dir fid + name, child fid.

	 */

	if (fanotify_event_dir_fh_len(event)) {

		info_type = info->name_len ? FAN_EVENT_INFO_TYPE_DFID_NAME :

					     FAN_EVENT_INFO_TYPE_DFID;

		ret = copy_fid_info_to_user(fanotify_event_fsid(event),

					    fanotify_info_dir_fh(info),

					    info_type,

					    fanotify_info_name(info),

					    info->name_len, buf, count);

		if (ret < 0)

			return ret;



		buf += ret;

		count -= ret;

		total_bytes += ret;

	}



	if (fanotify_event_object_fh_len(event)) {

		const char *dot = NULL;

		int dot_len = 0;



		if (fid_mode == FAN_REPORT_FID || info_type) {

			/*

			 * With only group flag FAN_REPORT_FID only type FID is

			 * reported. Second info record type is always FID.

			 */

			info_type = FAN_EVENT_INFO_TYPE_FID;

		} else if ((fid_mode & FAN_REPORT_NAME) &&

			   (event->mask & FAN_ONDIR)) {

			/*

			 * With group flag FAN_REPORT_NAME, if name was not

			 * recorded in an event on a directory, report the name

			 * "." with info type DFID_NAME.

			 */

			info_type = FAN_EVENT_INFO_TYPE_DFID_NAME;

			dot = ".";

			dot_len = 1;

		} else if ((event->mask & ALL_FSNOTIFY_DIRENT_EVENTS) ||

			   (event->mask & FAN_ONDIR)) {

			/*

			 * With group flag FAN_REPORT_DIR_FID, a single info

			 * record has type DFID for directory entry modification

			 * event and for event on a directory.

			 */

			info_type = FAN_EVENT_INFO_TYPE_DFID;

		} else {

			/*

			 * With group flags FAN_REPORT_DIR_FID|FAN_REPORT_FID,

			 * a single info record has type FID for event on a

			 * non-directory, when there is no directory to report.

			 * For example, on FAN_DELETE_SELF event.

			 */

			info_type = FAN_EVENT_INFO_TYPE_FID;

		}



		ret = copy_fid_info_to_user(fanotify_event_fsid(event),

					    fanotify_event_object_fh(event),

					    info_type, dot, dot_len,

					    buf, count);

		if (ret < 0)

			return ret;



		buf += ret;

		count -= ret;

		total_bytes += ret;

	}



	return total_bytes;

}



static ssize_t copy_event_to_user(struct fsnotify_group *group,

				  struct fanotify_event *event,

				  char __user *buf, size_t count)
@@ -408,15 +488,14 @@ static ssize_t copy_event_to_user(struct fsnotify_group *group, 
	struct fanotify_event_metadata metadata;

	struct path *path = fanotify_event_path(event);

	struct fanotify_info *info = fanotify_event_info(event);

	unsigned int fid_mode = FAN_GROUP_FLAG(group, FANOTIFY_FID_BITS);

	unsigned int info_mode = FAN_GROUP_FLAG(group, FANOTIFY_INFO_MODES);

	struct file *f = NULL;

	int ret, fd = FAN_NOFD;

	int info_type = 0;



	pr_debug("%s: group=%p event=%p\n", __func__, group, event);



	metadata.event_len = FAN_EVENT_METADATA_LEN +

				fanotify_event_info_len(fid_mode, event);

				fanotify_event_info_len(info_mode, event);

	metadata.metadata_len = FAN_EVENT_METADATA_LEN;

	metadata.vers = FANOTIFY_METADATA_VERSION;

	metadata.reserved = 0;
@@ -465,69 +544,11 @@ static ssize_t copy_event_to_user(struct fsnotify_group *group, 
	if (f)

		fd_install(fd, f);



	/* Event info records order is: dir fid + name, child fid */

	if (fanotify_event_dir_fh_len(event)) {

		info_type = info->name_len ? FAN_EVENT_INFO_TYPE_DFID_NAME :

					     FAN_EVENT_INFO_TYPE_DFID;

		ret = copy_fid_info_to_user(fanotify_event_fsid(event),

					    fanotify_info_dir_fh(info),

					    info_type,

					    fanotify_info_name(info),

					    info->name_len, buf, count);

		if (ret < 0)

			goto out_close_fd;



		buf += ret;

		count -= ret;

	}



	if (fanotify_event_object_fh_len(event)) {

		const char *dot = NULL;

		int dot_len = 0;



		if (fid_mode == FAN_REPORT_FID || info_type) {

			/*

			 * With only group flag FAN_REPORT_FID only type FID is

			 * reported. Second info record type is always FID.

			 */

			info_type = FAN_EVENT_INFO_TYPE_FID;

		} else if ((fid_mode & FAN_REPORT_NAME) &&

			   (event->mask & FAN_ONDIR)) {

			/*

			 * With group flag FAN_REPORT_NAME, if name was not

			 * recorded in an event on a directory, report the

			 * name "." with info type DFID_NAME.

			 */

			info_type = FAN_EVENT_INFO_TYPE_DFID_NAME;

			dot = ".";

			dot_len = 1;

		} else if ((event->mask & ALL_FSNOTIFY_DIRENT_EVENTS) ||

			   (event->mask & FAN_ONDIR)) {

			/*

			 * With group flag FAN_REPORT_DIR_FID, a single info

			 * record has type DFID for directory entry modification

			 * event and for event on a directory.

			 */

			info_type = FAN_EVENT_INFO_TYPE_DFID;

		} else {

			/*

			 * With group flags FAN_REPORT_DIR_FID|FAN_REPORT_FID,

			 * a single info record has type FID for event on a

			 * non-directory, when there is no directory to report.

			 * For example, on FAN_DELETE_SELF event.

			 */

			info_type = FAN_EVENT_INFO_TYPE_FID;

		}



		ret = copy_fid_info_to_user(fanotify_event_fsid(event),

					    fanotify_event_object_fh(event),

					    info_type, dot, dot_len,

	if (info_mode) {

		ret = copy_info_records_to_user(event, info, info_mode,

						buf, count);

		if (ret < 0)

			goto out_close_fd;



		buf += ret;

		count -= ret;

	}



	return metadata.event_len;

include/linux/fanotify.h

+2 −0
Original line number Diff line number Diff line
@@ -27,6 +27,8 @@ extern struct ctl_table fanotify_table[]; /* for sysctl */ 


#define FANOTIFY_FID_BITS	(FAN_REPORT_FID | FAN_REPORT_DFID_NAME)



#define FANOTIFY_INFO_MODES	(FANOTIFY_FID_BITS)



/*

 * fanotify_init() flags that require CAP_SYS_ADMIN.

 * We do not allow unprivileged groups to request permission events.