linux-hardening - [PATCH 08/21] dmaengine: sa11x0: Annotate struct sa11x0_dma_desc with __counted

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Date:   Thu, 17 Aug 2023 16:58:45 -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 08/21] dmaengine: sa11x0: Annotate struct sa11x0_dma_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 sa11x0_dma_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/sa11x0-dma.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/dma/sa11x0-dma.c b/drivers/dma/sa11x0-dma.c
index a29c13cae716..e5849622f198 100644
--- a/drivers/dma/sa11x0-dma.c
+++ b/drivers/dma/sa11x0-dma.c
@@ -78,7 +78,7 @@ struct sa11x0_dma_desc {
 	bool			cyclic;
 
 	unsigned		sglen;
-	struct sa11x0_dma_sg	sg[];
+	struct sa11x0_dma_sg	sg[] __counted_by(sglen);
 };
 
 struct sa11x0_dma_phy;
@@ -558,6 +558,7 @@ static struct dma_async_tx_descriptor *sa11x0_dma_prep_slave_sg(
 		dev_dbg(chan->device->dev, "vchan %p: kzalloc failed\n", &c->vc);
 		return NULL;
 	}
+	txd->sglen = j;
 
 	j = 0;
 	for_each_sg(sg, sgent, sglen, i) {
@@ -593,7 +594,6 @@ static struct dma_async_tx_descriptor *sa11x0_dma_prep_slave_sg(
 
 	txd->ddar = c->ddar;
 	txd->size = size;
-	txd->sglen = j;
 
 	dev_dbg(chan->device->dev, "vchan %p: txd %p: size %zu nr %u\n",
 		&c->vc, &txd->vd, txd->size, txd->sglen);
@@ -628,6 +628,7 @@ static struct dma_async_tx_descriptor *sa11x0_dma_prep_dma_cyclic(
 		dev_dbg(chan->device->dev, "vchan %p: kzalloc failed\n", &c->vc);
 		return NULL;
 	}
+	txd->sglen = sglen;
 
 	for (i = k = 0; i < size / period; i++) {
 		size_t tlen, len = period;
@@ -653,7 +654,6 @@ static struct dma_async_tx_descriptor *sa11x0_dma_prep_dma_cyclic(
 
 	txd->ddar = c->ddar;
 	txd->size = size;
-	txd->sglen = sglen;
 	txd->cyclic = 1;
 	txd->period = sgperiod;
 
-- 
2.34.1