linux-kernel - [PATCH] dmaengine: ep93xx_dma: Annotate struct ep93xx_dma_engine with __counted

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Date:   Thu, 28 Sep 2023 16:43:42 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Vinod Koul <vkoul@...nel.org>
Cc:     Kees Cook <keescook@...omium.org>,
        Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Tom Rix <trix@...hat.com>, dmaengine@...r.kernel.org,
        llvm@...ts.linux.dev,
        "Gustavo A. R. Silva" <gustavoars@...nel.org>,
        linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: [PATCH] dmaengine: ep93xx_dma: Annotate struct ep93xx_dma_engine 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 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 ep93xx_dma_engine.

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

Cc: Vinod Koul <vkoul@...nel.org>
Cc: Nathan Chancellor <nathan@...nel.org>
Cc: Nick Desaulniers <ndesaulniers@...gle.com>
Cc: Tom Rix <trix@...hat.com>
Cc: dmaengine@...r.kernel.org
Cc: llvm@...ts.linux.dev
Signed-off-by: Kees Cook <keescook@...omium.org>
---
 drivers/dma/ep93xx_dma.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/dma/ep93xx_dma.c b/drivers/dma/ep93xx_dma.c
index 5c4a448a1254..d6c60635e90d 100644
--- a/drivers/dma/ep93xx_dma.c
+++ b/drivers/dma/ep93xx_dma.c
@@ -213,7 +213,7 @@ struct ep93xx_dma_engine {
 #define INTERRUPT_NEXT_BUFFER	2
 
 	size_t			num_channels;
-	struct ep93xx_dma_chan	channels[];
+	struct ep93xx_dma_chan	channels[] __counted_by(num_channels);
 };
 
 static inline struct device *chan2dev(struct ep93xx_dma_chan *edmac)
-- 
2.34.1