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From: Kees Cook <keescook@chromium.org>
To: Keith Packard <keithp@keithp.com>
Cc: linux-kernel@vger.kernel.org,
	"Gustavo A. R. Silva" <gustavoars@kernel.org>,
	Arnd Bergmann <arnd@arndb.de>, Kalle Valo <kvalo@codeaurora.org>,
	"David S. Miller" <davem@davemloft.net>,
	Jakub Kicinski <kuba@kernel.org>,
	Nilesh Javali <njavali@marvell.com>,
	Manish Rangankar <mrangankar@marvell.com>,
	GR-QLogic-Storage-Upstream@marvell.com,
	"James E.J. Bottomley" <jejb@linux.ibm.com>,
	"Martin K. Petersen" <martin.petersen@oracle.com>,
	Larry Finger <Larry.Finger@lwfinger.net>,
	Phillip Potter <phil@philpotter.co.uk>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Florian Schilhabel <florian.c.schilhabel@googlemail.com>,
	Johannes Berg <johannes@sipsolutions.net>,
	Christophe JAILLET <christophe.jaillet@wanadoo.fr>,
	Fabio Aiuto <fabioaiuto83@gmail.com>,
	Ross Schmidt <ross.schm.dev@gmail.com>,
	Marco Cesati <marcocesati@gmail.com>,
	ath10k@lists.infradead.org, linux-wireless@vger.kernel.org,
	netdev@vger.kernel.org, linux-scsi@vger.kernel.org,
	linux-staging@lists.linux.dev,
	Rasmus Villemoes <linux@rasmusvillemoes.dk>,
	Dan Williams <dan.j.williams@intel.com>,
	Daniel Vetter <daniel.vetter@ffwll.ch>,
	clang-built-linux@googlegroups.com,
	linux-hardening@vger.kernel.org
Subject: Re: [PATCH v2 3/5] treewide: Replace 0-element memcpy() destinations with flexible arrays
Date: Wed, 25 Aug 2021 22:51:20 -0700	[thread overview]
Message-ID: <202108252250.C1DAEE5@keescook> (raw)
In-Reply-To: <87r1egpym5.fsf@keithp.com>

On Wed, Aug 25, 2021 at 10:24:18PM -0700, Keith Packard wrote:
> Kees Cook <keescook@chromium.org> writes:
> 
> > In some cases, use of the flex_array() helper is needed when a flexible
> > array is part of a union.
> 
> The code below seems to show that the helper is also needed when the
> flexible array is the only member of a struct? Or is this just an
> extension of the 'part of a union' clause?

That's correct. I have that documented in the DECLARE_FLEX_ARRAY macro
itself, but I mis-spoke in this changelog here (the uses were for "alone
in a struct"). I've adjusted the changelog now. :)

Thanks!

-Kees

> 
> > @@ -160,7 +160,7 @@ struct bmi_cmd {
> >  
> >  union bmi_resp {
> >  	struct {
> > -		u8 payload[0];
> > +		DECLARE_FLEX_ARRAY(u8, payload);
> >  	} read_mem;
> >  	struct {
> >  		__le32 result;
> 
> -- 
> -keith



-- 
Kees Cook

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WARNING: multiple messages have this Message-ID (diff)
From: Kees Cook <keescook@chromium.org>
To: Keith Packard <keithp@keithp.com>
Cc: linux-kernel@vger.kernel.org,
	"Gustavo A. R. Silva" <gustavoars@kernel.org>,
	Arnd Bergmann <arnd@arndb.de>, Kalle Valo <kvalo@codeaurora.org>,
	"David S. Miller" <davem@davemloft.net>,
	Jakub Kicinski <kuba@kernel.org>,
	Nilesh Javali <njavali@marvell.com>,
	Manish Rangankar <mrangankar@marvell.com>,
	GR-QLogic-Storage-Upstream@marvell.com,
	"James E.J. Bottomley" <jejb@linux.ibm.com>,
	"Martin K. Petersen" <martin.petersen@oracle.com>,
	Larry Finger <Larry.Finger@lwfinger.net>,
	Phillip Potter <phil@philpotter.co.uk>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Florian Schilhabel <florian.c.schilhabel@googlemail.com>,
	Johannes Berg <johannes@sipsolutions.net>,
	Christophe JAILLET <christophe.jaillet@wanadoo.fr>,
	Fabio Aiuto <fabioaiuto83@gmail.com>,
	Ross Schmidt <ross.schm.dev@gmail.com>,
	Marco Cesati <marcocesati@gmail.com>,
	ath10k@lists.infradead.org, linux-wireless@vger.kernel.org,
	netdev@vger.kernel.org, linux-scsi@vger.kernel.org,
	linux-staging@lists.linux.dev,
	Rasmus Villemoes <linux@rasmusvillemoes.dk>,
	Dan Williams <dan.j.williams@intel.com>,
	Daniel Vetter <daniel.vetter@ffwll.ch>,
	clang-built-linux@googlegroups.com,
	linux-hardening@vger.kernel.org
Subject: Re: [PATCH v2 3/5] treewide: Replace 0-element memcpy() destinations with flexible arrays
Date: Wed, 25 Aug 2021 22:51:20 -0700	[thread overview]
Message-ID: <202108252250.C1DAEE5@keescook> (raw)
In-Reply-To: <87r1egpym5.fsf@keithp.com>

On Wed, Aug 25, 2021 at 10:24:18PM -0700, Keith Packard wrote:
> Kees Cook <keescook@chromium.org> writes:
> 
> > In some cases, use of the flex_array() helper is needed when a flexible
> > array is part of a union.
> 
> The code below seems to show that the helper is also needed when the
> flexible array is the only member of a struct? Or is this just an
> extension of the 'part of a union' clause?

That's correct. I have that documented in the DECLARE_FLEX_ARRAY macro
itself, but I mis-spoke in this changelog here (the uses were for "alone
in a struct"). I've adjusted the changelog now. :)

Thanks!

-Kees

> 
> > @@ -160,7 +160,7 @@ struct bmi_cmd {
> >  
> >  union bmi_resp {
> >  	struct {
> > -		u8 payload[0];
> > +		DECLARE_FLEX_ARRAY(u8, payload);
> >  	} read_mem;
> >  	struct {
> >  		__le32 result;
> 
> -- 
> -keith



-- 
Kees Cook

  reply	other threads:[~2021-08-26  5:52 UTC|newest]

Thread overview: 28+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-26  5:04 [PATCH v2 0/5] Enable -Warray-bounds and -Wzero-length-bounds Kees Cook
2021-08-26  5:04 ` [PATCH v2 1/5] stddef: Add flexible array union helper Kees Cook
2021-08-26  5:04 ` [PATCH v2 2/5] treewide: Replace open-coded flex arrays in unions Kees Cook
2021-08-26  5:04   ` Kees Cook
2021-08-26  6:24   ` Marc Kleine-Budde
2021-08-26  6:24     ` Marc Kleine-Budde
2021-08-27 16:08     ` Kees Cook
2021-08-27 16:08       ` Kees Cook
2021-08-27 17:08       ` Marc Kleine-Budde
2021-08-27 17:08         ` Marc Kleine-Budde
2021-08-27 16:17     ` Kees Cook
2021-08-27 16:17       ` Kees Cook
2021-08-28  7:31       ` Vincent MAILHOL
2021-08-28  7:31         ` Vincent MAILHOL
2021-08-26  7:36   ` Vincent MAILHOL
2021-08-26  7:36     ` Vincent MAILHOL
2021-08-26 15:39     ` Kees Cook
2021-08-26 15:39       ` Kees Cook
2021-08-26  5:04 ` [PATCH v2 3/5] treewide: Replace 0-element memcpy() destinations with flexible arrays Kees Cook
2021-08-26  5:04   ` Kees Cook
2021-08-26  5:24   ` Keith Packard
2021-08-26  5:24     ` Keith Packard
2021-08-26  5:51     ` Kees Cook [this message]
2021-08-26  5:51       ` Kees Cook
2021-08-26  5:04 ` [PATCH v2 4/5] Makefile: Enable -Warray-bounds Kees Cook
2021-08-26  5:04 ` [PATCH v2 5/5] Makefile: Enable -Wzero-length-bounds Kees Cook
2021-08-27  9:25 ` [PATCH v2 1/5] stddef: Add flexible array union helper Vincent Mailhol
2021-08-27 15:39   ` Kees Cook

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