linux-kernel - [PATCH] clk: samsung: exynos-clkout: Assign .num before accessing .hws

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Message-Id: <20251124-exynos-clkout-fix-ubsan-bounds-error-v1-1-224a5282514b@kernel.org>
Date: Mon, 24 Nov 2025 12:11:06 -0700
From: Nathan Chancellor <nathan@...nel.org>
To: Krzysztof Kozlowski <krzk@...nel.org>, 
 Sylwester Nawrocki <s.nawrocki@...sung.com>, 
 Chanwoo Choi <cw00.choi@...sung.com>, Alim Akhtar <alim.akhtar@...sung.com>, 
 Michael Turquette <mturquette@...libre.com>, 
 Stephen Boyd <sboyd@...nel.org>, Kees Cook <kees@...nel.org>, 
 "Gustavo A. R. Silva" <gustavoars@...nel.org>
Cc: Salvatore Bonaccorso <carnil@...ian.org>, 
 linux-samsung-soc@...r.kernel.org, linux-clk@...r.kernel.org, 
 linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org, 
 linux-hardening@...r.kernel.org, stable@...r.kernel.org, 
 Jochen Sprickerhof <jochen@...ickerhof.de>, 
 Nathan Chancellor <nathan@...nel.org>
Subject: [PATCH] clk: samsung: exynos-clkout: Assign .num before accessing
 .hws

Commit f316cdff8d67 ("clk: Annotate struct clk_hw_onecell_data with
__counted_by") annotated the hws member of 'struct clk_hw_onecell_data'
with __counted_by, which informs the bounds sanitizer (UBSAN_BOUNDS)
about the number of elements in .hws[], so that it can warn when .hws[]
is accessed out of bounds. As noted in that change, the __counted_by
member must be initialized with the number of elements before the first
array access happens, otherwise there will be a warning from each access
prior to the initialization because the number of elements is zero. This
occurs in exynos_clkout_probe() due to .num being assigned after .hws[]
has been accessed:

  UBSAN: array-index-out-of-bounds in drivers/clk/samsung/clk-exynos-clkout.c:178:18
  index 0 is out of range for type 'clk_hw *[*]'

Move the .num initialization to before the first access of .hws[],
clearing up the warning.

Cc: stable@...r.kernel.org
Fixes: f316cdff8d67 ("clk: Annotate struct clk_hw_onecell_data with __counted_by")
Reported-by: Jochen Sprickerhof <jochen@...ickerhof.de>
Closes: https://lore.kernel.org/aSIYDN5eyKFKoXKL@eldamar.lan/
Tested-by: Jochen Sprickerhof <jochen@...ickerhof.de>
Signed-off-by: Nathan Chancellor <nathan@...nel.org>
---
 drivers/clk/samsung/clk-exynos-clkout.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/clk/samsung/clk-exynos-clkout.c b/drivers/clk/samsung/clk-exynos-clkout.c
index 5f1a4f5e2e59..5b21025338bd 100644
--- a/drivers/clk/samsung/clk-exynos-clkout.c
+++ b/drivers/clk/samsung/clk-exynos-clkout.c
@@ -175,6 +175,7 @@ static int exynos_clkout_probe(struct platform_device *pdev)
 	clkout->mux.shift = EXYNOS_CLKOUT_MUX_SHIFT;
 	clkout->mux.lock = &clkout->slock;

+	clkout->data.num = EXYNOS_CLKOUT_NR_CLKS;
 	clkout->data.hws[0] = clk_hw_register_composite(NULL, "clkout",
 				parent_names, parent_count, &clkout->mux.hw,
 				&clk_mux_ops, NULL, NULL, &clkout->gate.hw,
@@ -185,7 +186,6 @@ static int exynos_clkout_probe(struct platform_device *pdev)
 		goto err_unmap;
 	}

-	clkout->data.num = EXYNOS_CLKOUT_NR_CLKS;
 	ret = of_clk_add_hw_provider(clkout->np, of_clk_hw_onecell_get, &clkout->data);
 	if (ret)
 		goto err_clk_unreg;

---
base-commit: b6430552c8cd95e90bb842ce2f421e7a5381859f
change-id: 20251124-exynos-clkout-fix-ubsan-bounds-error-93071375ec78

Best regards,
--  
Nathan Chancellor <nathan@...nel.org>