Hello Amir,
On Mon, 17 Feb 2020 at 15:10, Amir Goldstein <amir73il@xxxxxxxxx> wrote:
>
> Report event FAN_DIR_MODIFY with name in a variable length record similar
> to how fid's are reported. With name info reporting implemented, setting
> FAN_DIR_MODIFY in mark mask is now allowed.
I see this was merged for 5.7. Would you be able to send a man-pages
patch that documents this new feature please.
Cheers,
Michael
>
> When events are reported with name, the reported fid identifies the
> directory and the name follows the fid. The info record type for this
> event info is FAN_EVENT_INFO_TYPE_DFID_NAME.
>
> For now, all reported events have at most one info record which is
> either FAN_EVENT_INFO_TYPE_FID or FAN_EVENT_INFO_TYPE_DFID_NAME (for
> FAN_DIR_MODIFY). Later on, events "on child" will report both records.
>
> There are several ways that an application can use this information:
>
> 1. When watching a single directory, the name is always relative to
> the watched directory, so application need to fstatat(2) the name
> relative to the watched directory.
>
> 2. When watching a set of directories, the application could keep a map
> of dirfd for all watched directories and hash the map by fid obtained
> with name_to_handle_at(2). When getting a name event, the fid in the
> event info could be used to lookup the base dirfd in the map and then
> call fstatat(2) with that dirfd.
>
> 3. When watching a filesystem (FAN_MARK_FILESYSTEM) or a large set of
> directories, the application could use open_by_handle_at(2) with the fid
> in event info to obtain dirfd for the directory where event happened and
> call fstatat(2) with this dirfd.
>
> The last option scales better for a large number of watched directories.
> The first two options may be available in the future also for non
> privileged fanotify watchers, because open_by_handle_at(2) requires
> the CAP_DAC_READ_SEARCH capability.
>
> Signed-off-by: Amir Goldstein <amir73il@xxxxxxxxx>
> ---
> fs/notify/fanotify/fanotify.c | 2 +-
> fs/notify/fanotify/fanotify_user.c | 120 ++++++++++++++++++++++-------
> include/linux/fanotify.h | 3 +-
> include/uapi/linux/fanotify.h | 1 +
> 4 files changed, 98 insertions(+), 28 deletions(-)
>
> diff --git a/fs/notify/fanotify/fanotify.c b/fs/notify/fanotify/fanotify.c
> index fc75dc53a218..b651c18d3a93 100644
> --- a/fs/notify/fanotify/fanotify.c
> +++ b/fs/notify/fanotify/fanotify.c
> @@ -478,7 +478,7 @@ static int fanotify_handle_event(struct fsnotify_group *group,
> BUILD_BUG_ON(FAN_OPEN_EXEC != FS_OPEN_EXEC);
> BUILD_BUG_ON(FAN_OPEN_EXEC_PERM != FS_OPEN_EXEC_PERM);
>
> - BUILD_BUG_ON(HWEIGHT32(ALL_FANOTIFY_EVENT_BITS) != 19);
> + BUILD_BUG_ON(HWEIGHT32(ALL_FANOTIFY_EVENT_BITS) != 20);
>
> mask = fanotify_group_event_mask(group, iter_info, mask, data,
> data_type);
> diff --git a/fs/notify/fanotify/fanotify_user.c b/fs/notify/fanotify/fanotify_user.c
> index 284f3548bb79..a1bafc21ebbb 100644
> --- a/fs/notify/fanotify/fanotify_user.c
> +++ b/fs/notify/fanotify/fanotify_user.c
> @@ -51,20 +51,32 @@ struct kmem_cache *fanotify_name_event_cachep __read_mostly;
> struct kmem_cache *fanotify_perm_event_cachep __read_mostly;
>
> #define FANOTIFY_EVENT_ALIGN 4
> +#define FANOTIFY_INFO_HDR_LEN \
> + (sizeof(struct fanotify_event_info_fid) + sizeof(struct file_handle))
>
> -static int fanotify_fid_info_len(struct fanotify_fid_hdr *fh)
> +static int fanotify_fid_info_len(int fh_len, int name_len)
> {
> - return roundup(sizeof(struct fanotify_event_info_fid) +
> - sizeof(struct file_handle) + fh->len,
> - FANOTIFY_EVENT_ALIGN);
> + int info_len = fh_len;
> +
> + if (name_len)
> + info_len += name_len + 1;
> +
> + return roundup(FANOTIFY_INFO_HDR_LEN + info_len, FANOTIFY_EVENT_ALIGN);
> }
>
> static int fanotify_event_info_len(struct fanotify_event *event)
> {
> - if (!fanotify_event_has_fid(event))
> - return 0;
> + int info_len = 0;
> +
> + if (fanotify_event_has_fid(event))
> + info_len += fanotify_fid_info_len(event->fh.len, 0);
> +
> + if (fanotify_event_has_dfid_name(event)) {
> + info_len += fanotify_fid_info_len(event->dfh.len,
> + fanotify_event_name_len(event));
> + }
>
> - return fanotify_fid_info_len(&event->fh);
> + return info_len;
> }
>
> /*
> @@ -210,23 +222,34 @@ static int process_access_response(struct fsnotify_group *group,
> return -ENOENT;
> }
>
> -static int copy_fid_to_user(__kernel_fsid_t *fsid, struct fanotify_fid_hdr *fh,
> - struct fanotify_fid *fid, char __user *buf)
> +static int copy_info_to_user(__kernel_fsid_t *fsid, struct fanotify_fid_hdr *fh,
> + struct fanotify_fid *fid, const struct qstr *name,
> + char __user *buf, size_t count)
> {
> struct fanotify_event_info_fid info = { };
> struct file_handle handle = { };
> - unsigned char bounce[FANOTIFY_INLINE_FH_LEN], *data;
> + unsigned char bounce[max(FANOTIFY_INLINE_FH_LEN, DNAME_INLINE_LEN)];
> + const unsigned char *data;
> size_t fh_len = fh->len;
> - size_t len = fanotify_fid_info_len(fh);
> + size_t name_len = name ? name->len : 0;
> + size_t info_len = fanotify_fid_info_len(fh_len, name_len);
> + size_t len = info_len;
> +
> + pr_debug("%s: fh_len=%lu name_len=%lu, info_len=%lu, count=%lu\n",
> + __func__, fh_len, name_len, info_len, count);
>
> - if (!len)
> + if (!fh_len || (name && !name_len))
> return 0;
>
> - if (WARN_ON_ONCE(len < sizeof(info) + sizeof(handle) + fh_len))
> + if (WARN_ON_ONCE(len < sizeof(info) || len > count))
> return -EFAULT;
>
> - /* Copy event info fid header followed by vaiable sized file handle */
> - info.hdr.info_type = FAN_EVENT_INFO_TYPE_FID;
> + /*
> + * Copy event info fid header followed by vaiable sized file handle
> + * and optionally followed by vaiable sized filename.
> + */
> + info.hdr.info_type = name_len ? FAN_EVENT_INFO_TYPE_DFID_NAME :
> + FAN_EVENT_INFO_TYPE_FID;
> info.hdr.len = len;
> info.fsid = *fsid;
> if (copy_to_user(buf, &info, sizeof(info)))
> @@ -234,6 +257,9 @@ static int copy_fid_to_user(__kernel_fsid_t *fsid, struct fanotify_fid_hdr *fh,
>
> buf += sizeof(info);
> len -= sizeof(info);
> + if (WARN_ON_ONCE(len < sizeof(handle)))
> + return -EFAULT;
> +
> handle.handle_type = fh->type;
> handle.handle_bytes = fh_len;
> if (copy_to_user(buf, &handle, sizeof(handle)))
> @@ -241,9 +267,12 @@ static int copy_fid_to_user(__kernel_fsid_t *fsid, struct fanotify_fid_hdr *fh,
>
> buf += sizeof(handle);
> len -= sizeof(handle);
> + if (WARN_ON_ONCE(len < fh_len))
> + return -EFAULT;
> +
> /*
> - * For an inline fh, copy through stack to exclude the copy from
> - * usercopy hardening protections.
> + * For an inline fh and inline file name, copy through stack to exclude
> + * the copy from usercopy hardening protections.
> */
> data = fanotify_fid_fh(fid, fh_len);
> if (fh_len <= FANOTIFY_INLINE_FH_LEN) {
> @@ -253,14 +282,33 @@ static int copy_fid_to_user(__kernel_fsid_t *fsid, struct fanotify_fid_hdr *fh,
> if (copy_to_user(buf, data, fh_len))
> return -EFAULT;
>
> - /* Pad with 0's */
> buf += fh_len;
> len -= fh_len;
> +
> + if (name_len) {
> + /* Copy the filename with terminating null */
> + name_len++;
> + if (WARN_ON_ONCE(len < name_len))
> + return -EFAULT;
> +
> + data = name->name;
> + if (name_len <= DNAME_INLINE_LEN) {
> + memcpy(bounce, data, name_len);
> + data = bounce;
> + }
> + if (copy_to_user(buf, data, name_len))
> + return -EFAULT;
> +
> + buf += name_len;
> + len -= name_len;
> + }
> +
> + /* Pad with 0's */
> WARN_ON_ONCE(len < 0 || len >= FANOTIFY_EVENT_ALIGN);
> if (len > 0 && clear_user(buf, len))
> return -EFAULT;
>
> - return 0;
> + return info_len;
> }
>
> static ssize_t copy_event_to_user(struct fsnotify_group *group,
> @@ -282,12 +330,12 @@ static ssize_t copy_event_to_user(struct fsnotify_group *group,
> metadata.mask = event->mask & FANOTIFY_OUTGOING_EVENTS;
> metadata.pid = pid_vnr(event->pid);
>
> - if (fanotify_event_has_path(event)) {
> + if (FAN_GROUP_FLAG(group, FAN_REPORT_FID)) {
> + metadata.event_len += fanotify_event_info_len(event);
> + } else if (fanotify_event_has_path(event)) {
> fd = create_fd(group, event, &f);
> if (fd < 0)
> return fd;
> - } else if (fanotify_event_has_fid(event)) {
> - metadata.event_len += fanotify_event_info_len(event);
> }
> metadata.fd = fd;
>
> @@ -302,16 +350,36 @@ static ssize_t copy_event_to_user(struct fsnotify_group *group,
> if (copy_to_user(buf, &metadata, FAN_EVENT_METADATA_LEN))
> goto out_close_fd;
>
> + buf += FAN_EVENT_METADATA_LEN;
> + count -= FAN_EVENT_METADATA_LEN;
> +
> if (fanotify_is_perm_event(event->mask))
> FANOTIFY_PE(fsn_event)->fd = fd;
>
> - if (fanotify_event_has_path(event)) {
> + if (f)
> fd_install(fd, f);
> - } else if (fanotify_event_has_fid(event)) {
> - ret = copy_fid_to_user(&event->fsid, &event->fh, &event->fid,
> - buf + FAN_EVENT_METADATA_LEN);
> +
> + /* Event info records order is: dir fid + name, child fid */
> + if (fanotify_event_has_dfid_name(event)) {
> + struct fanotify_name_event *fne = FANOTIFY_NE(fsn_event);
> +
> + ret = copy_info_to_user(&event->fsid, &event->dfh, &fne->dfid,
> + &fne->name, buf, count);
> if (ret < 0)
> return ret;
> +
> + buf += ret;
> + count -= ret;
> + }
> +
> + if (fanotify_event_has_fid(event)) {
> + ret = copy_info_to_user(&event->fsid, &event->fh, &event->fid,
> + NULL, buf, count);
> + if (ret < 0)
> + return ret;
> +
> + buf += ret;
> + count -= ret;
> }
>
> return metadata.event_len;
> diff --git a/include/linux/fanotify.h b/include/linux/fanotify.h
> index b79fa9bb7359..3049a6c06d9e 100644
> --- a/include/linux/fanotify.h
> +++ b/include/linux/fanotify.h
> @@ -47,7 +47,8 @@
> * Directory entry modification events - reported only to directory
> * where entry is modified and not to a watching parent.
> */
> -#define FANOTIFY_DIRENT_EVENTS (FAN_MOVE | FAN_CREATE | FAN_DELETE)
> +#define FANOTIFY_DIRENT_EVENTS (FAN_MOVE | FAN_CREATE | FAN_DELETE | \
> + FAN_DIR_MODIFY)
>
> /* Events that can only be reported with data type FSNOTIFY_EVENT_INODE */
> #define FANOTIFY_INODE_EVENTS (FANOTIFY_DIRENT_EVENTS | \
> diff --git a/include/uapi/linux/fanotify.h b/include/uapi/linux/fanotify.h
> index 615fa2c87179..2b56e194b858 100644
> --- a/include/uapi/linux/fanotify.h
> +++ b/include/uapi/linux/fanotify.h
> @@ -117,6 +117,7 @@ struct fanotify_event_metadata {
> };
>
> #define FAN_EVENT_INFO_TYPE_FID 1
> +#define FAN_EVENT_INFO_TYPE_DFID_NAME 2
>
> /* Variable length info record following event metadata */
> struct fanotify_event_info_header {
> --
> 2.17.1
>
--
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Linux/UNIX System Programming Training: http://man7.org/training/
