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

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Message-Id: <4911B345-A37E-4FB9-9339-83029033EE4D@toblux.com>
Date: Sun, 25 Aug 2024 22:41:55 +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,
 linux-kernel@...r.kernel.org,
 linux-hardening@...r.kernel.org
Subject: Re: [PATCH] bcachefs: Annotate bch_replicas_entry_{v0,v1} with
 __counted_by()

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);
})

Thanks,
Thorsten