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

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Message-Id: <20240425-cbl-bcm-assign-counted-by-val-before-access-v1-2-e2db3b82d5ef@kernel.org>
Date: Thu, 25 Apr 2024 09:55:52 -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 2/2] clk: bcm: rpi: 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
raspberrypi_discover_clocks() due to ->num being assigned after ->hws
has been accessed:

  UBSAN: array-index-out-of-bounds in drivers/clk/bcm/clk-raspberrypi.c:374:4
  index 3 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-raspberrypi.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/clk/bcm/clk-raspberrypi.c b/drivers/clk/bcm/clk-raspberrypi.c
index 829406dc44a2..4d411408e4af 100644
--- a/drivers/clk/bcm/clk-raspberrypi.c
+++ b/drivers/clk/bcm/clk-raspberrypi.c
@@ -371,8 +371,8 @@ static int raspberrypi_discover_clocks(struct raspberrypi_clk *rpi,
 			if (IS_ERR(hw))
 				return PTR_ERR(hw);

-			data->hws[clks->id] = hw;
 			data->num = clks->id + 1;
+			data->hws[clks->id] = hw;
 		}

 		clks++;

-- 
2.44.0