linux-ext4 - Re: [PATCH v8 29/32] fanotify: Allow users to request FAN_FS

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Date:   Tue, 19 Oct 2021 08:57:34 +0300
From:   Amir Goldstein <amir73il@...il.com>
To:     Gabriel Krisman Bertazi <krisman@...labora.com>
Cc:     Jan Kara <jack@...e.com>, "Darrick J. Wong" <djwong@...nel.org>,
        Theodore Tso <tytso@....edu>,
        Dave Chinner <david@...morbit.com>,
        David Howells <dhowells@...hat.com>,
        Khazhismel Kumykov <khazhy@...gle.com>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        Ext4 <linux-ext4@...r.kernel.org>,
        Linux API <linux-api@...r.kernel.org>, kernel@...labora.com
Subject: Re: [PATCH v8 29/32] fanotify: Allow users to request FAN_FS_ERROR events

On Tue, Oct 19, 2021 at 3:04 AM Gabriel Krisman Bertazi
<krisman@...labora.com> wrote:
>
> Wire up the FAN_FS_ERROR event in the fanotify_mark syscall, allowing
> user space to request the monitoring of FAN_FS_ERROR events.
>
> These events are limited to filesystem marks, so check it is the
> case in the syscall handler.
>
> Signed-off-by: Gabriel Krisman Bertazi <krisman@...labora.com>
>
Reviewed-by: Amir Goldstein <amir73il@...il.com>

> ---
> Changes since v7:
>   - Move the verification closer to similar code (Amir)
> ---
>  fs/notify/fanotify/fanotify.c      | 2 +-
>  fs/notify/fanotify/fanotify_user.c | 4 ++++
>  include/linux/fanotify.h           | 6 +++++-
>  3 files changed, 10 insertions(+), 2 deletions(-)
>
> diff --git a/fs/notify/fanotify/fanotify.c b/fs/notify/fanotify/fanotify.c
> index 0f6694eadb63..20169b8d5ab7 100644
> --- a/fs/notify/fanotify/fanotify.c
> +++ b/fs/notify/fanotify/fanotify.c
> @@ -821,7 +821,7 @@ static int fanotify_handle_event(struct fsnotify_group *group, u32 mask,
>         BUILD_BUG_ON(FAN_OPEN_EXEC_PERM != FS_OPEN_EXEC_PERM);
>         BUILD_BUG_ON(FAN_FS_ERROR != FS_ERROR);
>
> -       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, dir);
> diff --git a/fs/notify/fanotify/fanotify_user.c b/fs/notify/fanotify/fanotify_user.c
> index b83c61c934d0..22dca806c7e2 100644
> --- a/fs/notify/fanotify/fanotify_user.c
> +++ b/fs/notify/fanotify/fanotify_user.c
> @@ -1535,6 +1535,10 @@ static int do_fanotify_mark(int fanotify_fd, unsigned int flags, __u64 mask,
>             group->priority == FS_PRIO_0)
>                 goto fput_and_out;
>
> +       if (mask & FAN_FS_ERROR &&
> +           mark_type != FAN_MARK_FILESYSTEM)
> +               goto fput_and_out;
> +
>         /*
>          * Events that do not carry enough information to report
>          * event->fd require a group that supports reporting fid.  Those
> diff --git a/include/linux/fanotify.h b/include/linux/fanotify.h
> index 52d464802d99..616af2ea20f3 100644
> --- a/include/linux/fanotify.h
> +++ b/include/linux/fanotify.h
> @@ -91,9 +91,13 @@ extern struct ctl_table fanotify_table[]; /* for sysctl */
>  #define FANOTIFY_INODE_EVENTS  (FANOTIFY_DIRENT_EVENTS | \
>                                  FAN_ATTRIB | FAN_MOVE_SELF | FAN_DELETE_SELF)
>
> +/* Events that can only be reported with data type FSNOTIFY_EVENT_ERROR */
> +#define FANOTIFY_ERROR_EVENTS  (FAN_FS_ERROR)
> +
>  /* Events that user can request to be notified on */
>  #define FANOTIFY_EVENTS                (FANOTIFY_PATH_EVENTS | \
> -                                FANOTIFY_INODE_EVENTS)
> +                                FANOTIFY_INODE_EVENTS | \
> +                                FANOTIFY_ERROR_EVENTS)
>
>  /* Events that require a permission response from user */
>  #define FANOTIFY_PERM_EVENTS   (FAN_OPEN_PERM | FAN_ACCESS_PERM | \
> --
> 2.33.0
>