Re: [PATCH v2 45/63] ath11k: Use memset_startat() for clearing queue descriptors

From: Kees Cook <keescook@chromium.org>
To: Kalle Valo <kvalo@codeaurora.org>
Cc: linux-kernel@vger.kernel.org,
	"David S. Miller" <davem@davemloft.net>,
	Jakub Kicinski <kuba@kernel.org>,
	ath11k@lists.infradead.org, linux-wireless@vger.kernel.org,
	netdev@vger.kernel.org,
	"Gustavo A. R. Silva" <gustavoars@kernel.org>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	dri-devel@lists.freedesktop.org, linux-staging@lists.linux.dev,
	linux-block@vger.kernel.org, linux-kbuild@vger.kernel.org,
	clang-built-linux@googlegroups.com,
	Rasmus Villemoes <linux@rasmusvillemoes.dk>,
	linux-hardening@vger.kernel.org
Subject: Re: [PATCH v2 45/63] ath11k: Use memset_startat() for clearing queue descriptors
Date: Sun, 22 Aug 2021 01:11:32 -0700	[thread overview]
Message-ID: <202108220107.3E26FE6C9C@keescook> (raw)
In-Reply-To: <87pmu7t83j.fsf@codeaurora.org>

On Sat, Aug 21, 2021 at 01:17:36PM +0300, Kalle Valo wrote:
> Kees Cook <keescook@chromium.org> writes:
> 
> > On Thu, Aug 19, 2021 at 04:19:37PM +0300, Kalle Valo wrote:
> >> Kees Cook <keescook@chromium.org> writes:
> >> 
> >> > In preparation for FORTIFY_SOURCE performing compile-time and run-time
> >> > field bounds checking for memset(), avoid intentionally writing across
> >> > neighboring fields.
> >> >
> >> > Use memset_startat() so memset() doesn't get confused about writing
> >> > beyond the destination member that is intended to be the starting point
> >> > of zeroing through the end of the struct. Additionally split up a later
> >> > field-spanning memset() so that memset() can reason about the size.
> >> >
> >> > Cc: Kalle Valo <kvalo@codeaurora.org>
> >> > Cc: "David S. Miller" <davem@davemloft.net>
> >> > Cc: Jakub Kicinski <kuba@kernel.org>
> >> > Cc: ath11k@lists.infradead.org
> >> > Cc: linux-wireless@vger.kernel.org
> >> > Cc: netdev@vger.kernel.org
> >> > Signed-off-by: Kees Cook <keescook@chromium.org>
> >> 
> >> To avoid conflicts I prefer taking this via my ath tree.
> >
> > The memset helpers are introduced as part of this series, so that makes
> > things more difficult. Do you want me to create a branch with the
> > helpers that you can merge?
> 
> Is this patch really worth the extra complexity? Why can't I apply this
> ath11k patch after the helpers have landed Linus' tree? That would be
> very simple.

Not singularly, no. But I have a bit of a catch-22 in that I can't turn
on greater FORTIFY strictness without first fixing the false positives,
and I can't fix the false positives in "other" trees without those trees
first having the helpers that get introduced by the FORTIFY series. :)

Anyway, since we're close to the merge window anyway, the FORTIFY series
won't land in 1 release at this point regardless, so I'll just get
the helpers landed and we can do the individual pieces once the merge
window closes.

Wheee :)

-- 
Kees Cook

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