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From:   Amir Goldstein <amir73il@gmail.com>
Date:   Tue, 19 Oct 2021 09:13:57 +0300
Message-ID: <CAOQ4uxgd42EW0KGVMjaG4RdLQHOaMMMZ7+0XY5+we4jRs1Nggg@mail.gmail.com>
Subject: Re: [PATCH v8 25/32] fanotify: Report fid entry even for zero-length file_handle
To:     Gabriel Krisman Bertazi <krisman@collabora.com>
Cc:     Jan Kara <jack@suse.com>, "Darrick J. Wong" <djwong@kernel.org>,
        Theodore Tso <tytso@mit.edu>,
        Dave Chinner <david@fromorbit.com>,
        David Howells <dhowells@redhat.com>,
        Khazhismel Kumykov <khazhy@google.com>,
        linux-fsdevel <linux-fsdevel@vger.kernel.org>,
        Ext4 <linux-ext4@vger.kernel.org>,
        Linux API <linux-api@vger.kernel.org>, kernel@collabora.com
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On Tue, Oct 19, 2021 at 3:03 AM Gabriel Krisman Bertazi
<krisman@collabora.com> wrote:
>
> Non-inode errors will reported with an empty file_handle.  In
> preparation for that, allow some events to print the FID record even if
> there isn't any file_handle encoded
>
> Even though FILEID_ROOT is used internally, make zero-length file
> handles be reported as FILEID_INVALID.
>
> Signed-off-by: Gabriel Krisman Bertazi <krisman@collabora.com>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>

> ---
>  fs/notify/fanotify/fanotify_user.c | 8 +++++---
>  1 file changed, 5 insertions(+), 3 deletions(-)
>
> diff --git a/fs/notify/fanotify/fanotify_user.c b/fs/notify/fanotify/fanotify_user.c
> index ae848306a017..cd962deefeb7 100644
> --- a/fs/notify/fanotify/fanotify_user.c
> +++ b/fs/notify/fanotify/fanotify_user.c
> @@ -339,9 +339,6 @@ static int copy_fid_info_to_user(__kernel_fsid_t *fsid, struct fanotify_fh *fh,
>         pr_debug("%s: fh_len=%zu name_len=%zu, info_len=%zu, count=%zu\n",
>                  __func__, fh_len, name_len, info_len, count);
>
> -       if (!fh_len)
> -               return 0;
> -
>         if (WARN_ON_ONCE(len < sizeof(info) || len > count))
>                 return -EFAULT;
>
> @@ -376,6 +373,11 @@ static int copy_fid_info_to_user(__kernel_fsid_t *fsid, struct fanotify_fh *fh,
>
>         handle.handle_type = fh->type;
>         handle.handle_bytes = fh_len;
> +
> +       /* Mangle handle_type for bad file_handle */
> +       if (!fh_len)
> +               handle.handle_type = FILEID_INVALID;
> +
>         if (copy_to_user(buf, &handle, sizeof(handle)))
>                 return -EFAULT;
>
> --
> 2.33.0
>