On Mon 27-03-23 20:22:53, Christian Brauner wrote:
> We generally try to avoid installing a file descriptor into the caller's
> file descriptor table just to close it again via close_fd() in case an
> error occurs. Instead we reserve a file descriptor but don't install it
> into the caller's file descriptor table yet. If we fail for other,
> unrelated reasons we can just close the reserved file descriptor and if
> we make it past all meaningful error paths we just install it. Fanotify
> gets this right already for one fd type but not for pidfds.
>
> Use the new pidfd_prepare() helper to reserve a pidfd and a pidfd file
> and switch to the more common fd allocation and installation pattern.
>
> Signed-off-by: Christian Brauner <brauner@xxxxxxxxxx>
Thanks for the improvement! It looks good to me. Feel free to add:
Acked-by: Jan Kara <jack@xxxxxxx>
Honza
> ---
> fs/notify/fanotify/fanotify_user.c | 13 +++++++++----
> 1 file changed, 9 insertions(+), 4 deletions(-)
>
> diff --git a/fs/notify/fanotify/fanotify_user.c b/fs/notify/fanotify/fanotify_user.c
> index 8f430bfad487..22fb1cf7e1fc 100644
> --- a/fs/notify/fanotify/fanotify_user.c
> +++ b/fs/notify/fanotify/fanotify_user.c
> @@ -663,7 +663,7 @@ static ssize_t copy_event_to_user(struct fsnotify_group *group,
> struct fanotify_info *info = fanotify_event_info(event);
> unsigned int info_mode = FAN_GROUP_FLAG(group, FANOTIFY_INFO_MODES);
> unsigned int pidfd_mode = info_mode & FAN_REPORT_PIDFD;
> - struct file *f = NULL;
> + struct file *f = NULL, *pidfd_file = NULL;
> int ret, pidfd = FAN_NOPIDFD, fd = FAN_NOFD;
>
> pr_debug("%s: group=%p event=%p\n", __func__, group, event);
> @@ -718,7 +718,7 @@ static ssize_t copy_event_to_user(struct fsnotify_group *group,
> !pid_has_task(event->pid, PIDTYPE_TGID)) {
> pidfd = FAN_NOPIDFD;
> } else {
> - pidfd = pidfd_create(event->pid, 0);
> + pidfd = pidfd_prepare(event->pid, 0, &pidfd_file);
> if (pidfd < 0)
> pidfd = FAN_EPIDFD;
> }
> @@ -751,6 +751,9 @@ static ssize_t copy_event_to_user(struct fsnotify_group *group,
> if (f)
> fd_install(fd, f);
>
> + if (pidfd_file)
> + fd_install(pidfd, pidfd_file);
> +
> return metadata.event_len;
>
> out_close_fd:
> @@ -759,8 +762,10 @@ static ssize_t copy_event_to_user(struct fsnotify_group *group,
> fput(f);
> }
>
> - if (pidfd >= 0)
> - close_fd(pidfd);
> + if (pidfd >= 0) {
> + put_unused_fd(pidfd);
> + fput(pidfd_file);
> + }
>
> return ret;
> }
>
> --
> 2.34.1
>
--
Jan Kara <jack@xxxxxxxx>
SUSE Labs, CR
