linux-hardening - [PATCH 12/21] dmaengine: stm32-dma: Annotate struct stm32_dma_desc with __counted

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Date:   Thu, 17 Aug 2023 16:58:49 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Vinod Koul <vkoul@...nel.org>
Cc:     Kees Cook <keescook@...omium.org>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        Alexandre Torgue <alexandre.torgue@...s.st.com>,
        dmaengine@...r.kernel.org,
        linux-stm32@...md-mailman.stormreply.com,
        linux-arm-kernel@...ts.infradead.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>,
        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-msm@...r.kernel.org,
        linux-tegra@...r.kernel.org, llvm@...ts.linux.dev,
        linux-hardening@...r.kernel.org
Subject: [PATCH 12/21] dmaengine: stm32-dma: Annotate struct stm32_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 stm32_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: Maxime Coquelin <mcoquelin.stm32@...il.com>
Cc: Alexandre Torgue <alexandre.torgue@...s.st.com>
Cc: dmaengine@...r.kernel.org
Cc: linux-stm32@...md-mailman.stormreply.com
Cc: linux-arm-kernel@...ts.infradead.org
Signed-off-by: Kees Cook <keescook@...omium.org>
---
 drivers/dma/stm32-dma.c | 11 ++++-------
 1 file changed, 4 insertions(+), 7 deletions(-)

diff --git a/drivers/dma/stm32-dma.c b/drivers/dma/stm32-dma.c
index 5c36811aa134..a732b3807b11 100644
--- a/drivers/dma/stm32-dma.c
+++ b/drivers/dma/stm32-dma.c
@@ -191,7 +191,7 @@ struct stm32_dma_desc {
 	struct virt_dma_desc vdesc;
 	bool cyclic;
 	u32 num_sgs;
-	struct stm32_dma_sg_req sg_req[];
+	struct stm32_dma_sg_req sg_req[] __counted_by(num_sgs);
 };
 
 /**
@@ -1105,6 +1105,7 @@ static struct dma_async_tx_descriptor *stm32_dma_prep_slave_sg(
 	desc = kzalloc(struct_size(desc, sg_req, sg_len), GFP_NOWAIT);
 	if (!desc)
 		return NULL;
+	desc->num_sgs = sg_len;
 
 	/* Set peripheral flow controller */
 	if (chan->dma_sconfig.device_fc)
@@ -1141,8 +1142,6 @@ static struct dma_async_tx_descriptor *stm32_dma_prep_slave_sg(
 			desc->sg_req[i].chan_reg.dma_sm1ar += sg_dma_len(sg);
 		desc->sg_req[i].chan_reg.dma_sndtr = nb_data_items;
 	}
-
-	desc->num_sgs = sg_len;
 	desc->cyclic = false;
 
 	return vchan_tx_prep(&chan->vchan, &desc->vdesc, flags);
@@ -1216,6 +1215,7 @@ static struct dma_async_tx_descriptor *stm32_dma_prep_dma_cyclic(
 	desc = kzalloc(struct_size(desc, sg_req, num_periods), GFP_NOWAIT);
 	if (!desc)
 		return NULL;
+	desc->num_sgs = num_periods;
 
 	for (i = 0; i < num_periods; i++) {
 		desc->sg_req[i].len = period_len;
@@ -1232,8 +1232,6 @@ static struct dma_async_tx_descriptor *stm32_dma_prep_dma_cyclic(
 		if (!chan->trig_mdma)
 			buf_addr += period_len;
 	}
-
-	desc->num_sgs = num_periods;
 	desc->cyclic = true;
 
 	return vchan_tx_prep(&chan->vchan, &desc->vdesc, flags);
@@ -1254,6 +1252,7 @@ static struct dma_async_tx_descriptor *stm32_dma_prep_dma_memcpy(
 	desc = kzalloc(struct_size(desc, sg_req, num_sgs), GFP_NOWAIT);
 	if (!desc)
 		return NULL;
+	desc->num_sgs = num_sgs;
 
 	threshold = chan->threshold;
 
@@ -1283,8 +1282,6 @@ static struct dma_async_tx_descriptor *stm32_dma_prep_dma_memcpy(
 		desc->sg_req[i].chan_reg.dma_sndtr = xfer_count;
 		desc->sg_req[i].len = xfer_count;
 	}
-
-	desc->num_sgs = num_sgs;
 	desc->cyclic = false;
 
 	return vchan_tx_prep(&chan->vchan, &desc->vdesc, flags);
-- 
2.34.1