linux-kernel - [PATCH 06/21] dmaengine: moxart-dma: Annotate struct moxart_desc with __counted

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Message-Id: <20230817235859.49846-6-keescook@chromium.org>
Date:   Thu, 17 Aug 2023 16:58:43 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Vinod Koul <vkoul@...nel.org>
Cc:     Kees Cook <keescook@...omium.org>, dmaengine@...r.kernel.org,
        Hector Martin <marcan@...can.st>,
        Sven Peter <sven@...npeter.dev>,
        Alyssa Rosenzweig <alyssa@...enzweig.io>,
        Ludovic Desroches <ludovic.desroches@...rochip.com>,
        Tudor Ambarus <tudor.ambarus@...aro.org>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Zhou Wang <wangzhou1@...ilicon.com>,
        Jie Hai <haijie1@...wei.com>, Andy Gross <agross@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konrad.dybcio@...aro.org>,
        Green Wan <green.wan@...ive.com>,
        Orson Zhai <orsonzhai@...il.com>,
        Baolin Wang <baolin.wang@...ux.alibaba.com>,
        Chunyan Zhang <zhang.lyra@...il.com>,
        Patrice Chotard <patrice.chotard@...s.st.com>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        Alexandre Torgue <alexandre.torgue@...s.st.com>,
        Laxman Dewangan <ldewangan@...dia.com>,
        Jon Hunter <jonathanh@...dia.com>,
        Thierry Reding <thierry.reding@...il.com>,
        Peter Ujfalusi <peter.ujfalusi@...il.com>,
        Kunihiko Hayashi <hayashi.kunihiko@...ionext.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Yu Kuai <yukuai3@...wei.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jordy Zomer <jordy@...ing.systems>,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Tom Rix <trix@...hat.com>, linux-kernel@...r.kernel.org,
        asahi@...ts.linux.dev, linux-arm-kernel@...ts.infradead.org,
        linux-arm-msm@...r.kernel.org,
        linux-stm32@...md-mailman.stormreply.com,
        linux-tegra@...r.kernel.org, llvm@...ts.linux.dev,
        linux-hardening@...r.kernel.org
Subject: [PATCH 06/21] dmaengine: moxart-dma: Annotate struct moxart_desc with __counted_by

Prepare for the coming implementation by GCC and Clang of the __counted_by
attribute. Flexible array members annotated with __counted_by can have
their accesses bounds-checked at run-time checking via CONFIG_UBSAN_BOUNDS
(for array indexing) and CONFIG_FORTIFY_SOURCE (for strcpy/memcpy-family
functions).

As found with Coccinelle[1], add __counted_by for struct moxart_desc.
Additionally, since the element count member must be set before accessing
the annotated flexible array member, move its initialization earlier.

[1] https://github.com/kees/kernel-tools/blob/trunk/coccinelle/examples/counted_by.cocci

Cc: Vinod Koul <vkoul@...nel.org>
Cc: dmaengine@...r.kernel.org
Signed-off-by: Kees Cook <keescook@...omium.org>
---
 drivers/dma/moxart-dma.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/drivers/dma/moxart-dma.c b/drivers/dma/moxart-dma.c
index 7565ad98ba66..c1dd5716a46d 100644
--- a/drivers/dma/moxart-dma.c
+++ b/drivers/dma/moxart-dma.c
@@ -124,7 +124,7 @@ struct moxart_desc {
 	unsigned int			dma_cycles;
 	struct virt_dma_desc		vd;
 	uint8_t				es;
-	struct moxart_sg		sg[];
+	struct moxart_sg		sg[] __counted_by(sglen);
 };
 
 struct moxart_chan {
@@ -309,6 +309,7 @@ static struct dma_async_tx_descriptor *moxart_prep_slave_sg(
 	d = kzalloc(struct_size(d, sg, sg_len), GFP_ATOMIC);
 	if (!d)
 		return NULL;
+	d->sglen = sg_len;
 
 	d->dma_dir = dir;
 	d->dev_addr = dev_addr;
@@ -319,8 +320,6 @@ static struct dma_async_tx_descriptor *moxart_prep_slave_sg(
 		d->sg[i].len = sg_dma_len(sgent);
 	}
 
-	d->sglen = sg_len;
-
 	ch->error = 0;
 
 	return vchan_tx_prep(&ch->vc, &d->vd, tx_flags);
-- 
2.34.1