linux-hardening - Re: [PATCH v4] [next] dlm: replace one-element array with fixed size array

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Date:   Tue, 11 Oct 2022 13:06:32 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Paulo Miguel Almeida <paulo.miguel.almeida.rodenas@...il.com>
Cc:     Christine Caulfield <ccaulfie@...hat.com>,
        David Teigland <teigland@...hat.com>, cluster-devel@...hat.com,
        linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: Re: [PATCH v4] [next] dlm: replace one-element array with fixed size
 array

On Wed, Oct 12, 2022 at 09:04:15AM +1300, Paulo Miguel Almeida wrote:
> One-element arrays are deprecated. So, replace one-element array with
> fixed size array member in struct dlm_ls, and refactor the rest of the
> code, accordingly.
> 
> Link: https://github.com/KSPP/linux/issues/79
> Link: https://github.com/KSPP/linux/issues/228
> Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101836
> Link: https://lore.kernel.org/lkml/Y0W5jkiXUkpNl4ap@mail.google.com/
> 
> Signed-off-by: Paulo Miguel Almeida <paulo.miguel.almeida.rodenas@...il.com>
> ---
> Changelog:
> 
> v4: resend patch using the right version number. Req: Gustavo Silva
> v3: replace one-element array with a fixed size array. Req: Kees Cook
> v2: patch resent as I had an issue with a <CRLF> char in my mail client
> v1: https://lore.kernel.org/lkml/Y0ICbf8tCtXMn+W0@mail.google.com/
> ---
>  fs/dlm/dlm_internal.h | 2 +-
>  fs/dlm/lockspace.c    | 2 +-
>  2 files changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/dlm/dlm_internal.h b/fs/dlm/dlm_internal.h
> index e34c3d2639a5..94fadb619ba0 100644
> --- a/fs/dlm/dlm_internal.h
> +++ b/fs/dlm/dlm_internal.h
> @@ -670,7 +670,7 @@ struct dlm_ls {
>  	void			*ls_ops_arg;
>  
>  	int			ls_namelen;
> -	char			ls_name[1];
> +	char			ls_name[DLM_LOCKSPACE_LEN + 1];
>  };
>  
>  /*
> diff --git a/fs/dlm/lockspace.c b/fs/dlm/lockspace.c
> index bae050df7abf..23de0d47cbc1 100644
> --- a/fs/dlm/lockspace.c
> +++ b/fs/dlm/lockspace.c
> @@ -473,7 +473,7 @@ static int new_lockspace(const char *name, const char *cluster,
>  
>  	error = -ENOMEM;
>  
> -	ls = kzalloc(sizeof(struct dlm_ls) + namelen, GFP_NOFS);
> +	ls = kzalloc(sizeof(struct dlm_ls), GFP_NOFS);
                     ^^^^^^^^^^^^^^^^^^^^
I think you forgot the suggestion Gustavo had here. :) Preferred style would
be:
	sizeof(*ls)

-- 
Kees Cook