linux-kernel - [PATCH] clk: s2mps11: initialise clk_hw_onecell_data::num before accessing ::hws[] in probe()

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Message-Id: <20250326-s2mps11-ubsan-v1-1-fcc6fce5c8a9@linaro.org>
Date: Wed, 26 Mar 2025 12:08:00 +0000
From: André Draszik <andre.draszik@...aro.org>
To: Krzysztof Kozlowski <krzk@...nel.org>, 
 Michael Turquette <mturquette@...libre.com>, 
 Stephen Boyd <sboyd@...nel.org>, Kees Cook <kees@...nel.org>, 
 "Gustavo A. R. Silva" <gustavoars@...nel.org>
Cc: linux-kernel@...r.kernel.org, linux-samsung-soc@...r.kernel.org, 
 linux-clk@...r.kernel.org, linux-hardening@...r.kernel.org, 
 stable@...r.kernel.org, 
 André Draszik <andre.draszik@...aro.org>
Subject: [PATCH] clk: s2mps11: initialise clk_hw_onecell_data::num before
 accessing ::hws[] in probe()

With UBSAN enabled, we're getting the following trace:

    UBSAN: array-index-out-of-bounds in .../drivers/clk/clk-s2mps11.c:186:3
    index 0 is out of range for type 'struct clk_hw *[] __counted_by(num)' (aka 'struct clk_hw *[]')

This is because commit f316cdff8d67 ("clk: Annotate struct
clk_hw_onecell_data with __counted_by") annotated the hws member of
that struct with __counted_by, which informs the bounds sanitizer 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 initialised
with the number of elements before the first array access happens,
otherwise there will be a warning from each access prior to the
initialisation because the number of elements is zero. This occurs in
s2mps11_clk_probe() due to ::num being assigned after ::hws access.

Move the assignment to satisfy the requirement of assign-before-access.

Cc: stable@...r.kernel.org
Fixes: f316cdff8d67 ("clk: Annotate struct clk_hw_onecell_data with __counted_by")
Signed-off-by: André Draszik <andre.draszik@...aro.org>
---
 drivers/clk/clk-s2mps11.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/clk/clk-s2mps11.c b/drivers/clk/clk-s2mps11.c
index 014db6386624071e173b5b940466301d2596400a..8ddf3a9a53dfd5bb52a05a3e02788a357ea77ad3 100644
--- a/drivers/clk/clk-s2mps11.c
+++ b/drivers/clk/clk-s2mps11.c
@@ -137,6 +137,8 @@ static int s2mps11_clk_probe(struct platform_device *pdev)
 	if (!clk_data)
 		return -ENOMEM;

+	clk_data->num = S2MPS11_CLKS_NUM;
+
 	switch (hwid) {
 	case S2MPS11X:
 		s2mps11_reg = S2MPS11_REG_RTC_CTRL;
@@ -186,7 +188,6 @@ static int s2mps11_clk_probe(struct platform_device *pdev)
 		clk_data->hws[i] = &s2mps11_clks[i].hw;
 	}

-	clk_data->num = S2MPS11_CLKS_NUM;
 	of_clk_add_hw_provider(s2mps11_clks->clk_np, of_clk_hw_onecell_get,
 			       clk_data);

---
base-commit: 9388ec571cb1adba59d1cded2300eeb11827679c
change-id: 20250326-s2mps11-ubsan-c90978e7bc04

Best regards,
-- 
André Draszik <andre.draszik@...aro.org>