linux-hardening - [PATCH 1/2] clk: bcm: dvp: Assign ->num before accessing ->hws

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Message-Id: <20240425-cbl-bcm-assign-counted-by-val-before-access-v1-1-e2db3b82d5ef@kernel.org>
Date: Thu, 25 Apr 2024 09:55:51 -0700
From: Nathan Chancellor <nathan@...nel.org>
To: Michael Turquette <mturquette@...libre.com>, 
 Stephen Boyd <sboyd@...nel.org>, 
 Florian Fainelli <florian.fainelli@...adcom.com>
Cc: Kees Cook <keescook@...omium.org>, 
 "Gustavo A. R. Silva" <gustavoars@...nel.org>, 
 bcm-kernel-feedback-list@...adcom.com, linux-clk@...r.kernel.org, 
 linux-rpi-kernel@...ts.infradead.org, linux-arm-kernel@...ts.infradead.org, 
 linux-hardening@...r.kernel.org, patches@...ts.linux.dev, 
 llvm@...ts.linux.dev, stable@...r.kernel.org, 
 Nathan Chancellor <nathan@...nel.org>
Subject: [PATCH 1/2] clk: bcm: dvp: 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 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
clk_dvp_probe() due to ->num being assigned after ->hws has been
accessed:

  UBSAN: array-index-out-of-bounds in drivers/clk/bcm/clk-bcm2711-dvp.c:59:2
  index 0 is out of range for type 'struct clk_hw *[] __counted_by(num)' (aka 'struct clk_hw *[]')

Move the ->num initialization to before the first access of ->hws, which
clears up the warning.

Cc: stable@...r.kernel.org
Fixes: f316cdff8d67 ("clk: Annotate struct clk_hw_onecell_data with __counted_by")
Signed-off-by: Nathan Chancellor <nathan@...nel.org>
---
 drivers/clk/bcm/clk-bcm2711-dvp.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/clk/bcm/clk-bcm2711-dvp.c b/drivers/clk/bcm/clk-bcm2711-dvp.c
index e4fbbf3c40fe..3cb235df9d37 100644
--- a/drivers/clk/bcm/clk-bcm2711-dvp.c
+++ b/drivers/clk/bcm/clk-bcm2711-dvp.c
@@ -56,6 +56,8 @@ static int clk_dvp_probe(struct platform_device *pdev)
 	if (ret)
 		return ret;

+	data->num = NR_CLOCKS;
+
 	data->hws[0] = clk_hw_register_gate_parent_data(&pdev->dev,
 							"hdmi0-108MHz",
 							&clk_dvp_parent, 0,
@@ -76,7 +78,6 @@ static int clk_dvp_probe(struct platform_device *pdev)
 		goto unregister_clk0;
 	}

-	data->num = NR_CLOCKS;
 	ret = of_clk_add_hw_provider(pdev->dev.of_node, of_clk_hw_onecell_get,
 				     data);
 	if (ret)

-- 
2.44.0