linux-ext4 - Re: [PATCH v7 25/28] fanotify: Allow users to request FAN_FS

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Date:   Fri, 15 Oct 2021 11:27:39 +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>,
        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>,
        Matthew Bobrowski <repnop@...gle.com>, kernel@...labora.com
Subject: Re: [PATCH v7 25/28] fanotify: Allow users to request FAN_FS_ERROR events

On Fri, Oct 15, 2021 at 12:39 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>
> ---
>  fs/notify/fanotify/fanotify.c      | 2 +-
>  fs/notify/fanotify/fanotify_user.c | 5 +++++
>  include/linux/fanotify.h           | 6 +++++-
>  3 files changed, 11 insertions(+), 2 deletions(-)
>
> diff --git a/fs/notify/fanotify/fanotify.c b/fs/notify/fanotify/fanotify.c
> index 47e28f418711..d449a23d603f 100644
> --- a/fs/notify/fanotify/fanotify.c
> +++ b/fs/notify/fanotify/fanotify.c
> @@ -827,7 +827,7 @@ 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 8f7c2f4ce674..5edfd7e3f356 100644
> --- a/fs/notify/fanotify/fanotify_user.c
> +++ b/fs/notify/fanotify/fanotify_user.c
> @@ -1585,6 +1585,11 @@ static int do_fanotify_mark(int fanotify_fd, unsigned int flags, __u64 mask,
>                 fsid = &__fsid;
>         }
>
> +       if (mask & FAN_FS_ERROR && mark_type != FAN_MARK_FILESYSTEM) {
> +               ret = -EINVAL;
> +               goto path_put_and_out;
> +       }
> +

Please move this up to the section where input args validity is checked
(i.e. before or after FANOTIFY_PERM_EVENTS check).
It is the correct context for this sort of check and ret is already
set to -EINVAL for the entire section.

Thanks,
Amir.