linux-hardening - [PATCH 13/21] dmaengine: stm32-mdma: Annotate struct stm32_mdma_desc with __counted

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Message-Id: <20230817235859.49846-13-keescook@chromium.org>
Date:   Thu, 17 Aug 2023 16:58:50 -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 13/21] dmaengine: stm32-mdma: Annotate struct stm32_mdma_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_mdma_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-mdma.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/drivers/dma/stm32-mdma.c b/drivers/dma/stm32-mdma.c
index 0de234022c6d..926d6ecf1274 100644
--- a/drivers/dma/stm32-mdma.c
+++ b/drivers/dma/stm32-mdma.c
@@ -224,7 +224,7 @@ struct stm32_mdma_desc {
 	u32 ccr;
 	bool cyclic;
 	u32 count;
-	struct stm32_mdma_desc_node node[];
+	struct stm32_mdma_desc_node node[] __counted_by(count);
 };
 
 struct stm32_mdma_dma_config {
@@ -321,6 +321,7 @@ static struct stm32_mdma_desc *stm32_mdma_alloc_desc(
 	desc = kzalloc(struct_size(desc, node, count), GFP_NOWAIT);
 	if (!desc)
 		return NULL;
+	desc->count = count;
 
 	for (i = 0; i < count; i++) {
 		desc->node[i].hwdesc =
@@ -330,8 +331,6 @@ static struct stm32_mdma_desc *stm32_mdma_alloc_desc(
 			goto err;
 	}
 
-	desc->count = count;
-
 	return desc;
 
 err:
-- 
2.34.1