linux-hardening - Re: [PATCH] bcachefs: Annotate bch_replicas_entry_{v0,v1} with __counted

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Message-Id: <6B15FD73-8FD5-4180-9190-FA8ABF7E88BB@toblux.com>
Date: Mon, 26 Aug 2024 01:08:29 +0200
From: Thorsten Blum <thorsten.blum@...lux.com>
To: Kent Overstreet <kent.overstreet@...ux.dev>
Cc: Kees Cook <kees@...nel.org>,
 "Gustavo A. R. Silva" <gustavoars@...nel.org>,
 linux-bcachefs@...r.kernel.org,
 LKML <linux-kernel@...r.kernel.org>,
 linux-hardening@...r.kernel.org
Subject: Re: [PATCH] bcachefs: Annotate bch_replicas_entry_{v0,v1} with
 __counted_by()

On 26. Aug 2024, at 00:56, Kent Overstreet <kent.overstreet@...ux.dev> wrote:
> On Sun, Aug 25, 2024 at 10:41:55PM GMT, Thorsten Blum wrote:
>> On 25. Aug 2024, at 20:43, Kent Overstreet <kent.overstreet@...ux.dev> wrote:
>>> On Sun, Aug 25, 2024 at 03:36:02PM GMT, Thorsten Blum wrote:
>>>> Add the __counted_by compiler attribute to the flexible array members
>>>> devs to improve access bounds-checking via CONFIG_UBSAN_BOUNDS and
>>>> CONFIG_FORTIFY_SOURCE.
>>>> 
>>>> Increment nr_devs before adding a new device to the devs array and
>>>> adjust the array indexes accordingly.
>>> 
>>> The nr_devs changes are pretty gross - please add a helper for that
>> 
>> How about a macro in replicas_format.h like this:
>> 
>> #define replicas_entry_add_dev(e, d) ({
>> 	(e)->nr_devs++;
>> 	(e)->devs[(e)->nr_devs - 1] = (d);
>> })
> 
> Does it need to be a macro?

It could also be two functions, one for each struct.

Which one do you prefer?