linux-ext4 - Re: [PATCH v8 25/32] fanotify: Report fid entry even for zero-length file

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Date:   Tue, 19 Oct 2021 16:08:45 +0200
From:   Jan Kara <jack@...e.cz>
To:     Gabriel Krisman Bertazi <krisman@...labora.com>
Cc:     jack@...e.com, amir73il@...il.com, djwong@...nel.org,
        tytso@....edu, david@...morbit.com, dhowells@...hat.com,
        khazhy@...gle.com, linux-fsdevel@...r.kernel.org,
        linux-ext4@...r.kernel.org, linux-api@...r.kernel.org,
        kernel@...labora.com
Subject: Re: [PATCH v8 25/32] fanotify: Report fid entry even for zero-length
 file_handle

On Mon 18-10-21 21:00:08, Gabriel Krisman Bertazi 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@...labora.com>

I suppose you need to move fanotify_has_object_fh() change from patch 27
here. Otherwise the change looks good so feel free to add:

Reviewed-by: Jan Kara <jack@...e.cz>

								Honza

> ---
>  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
> 
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR