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

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Message-ID: <43a26fb44baa417a4fe2663d86909c0e@kernel.org>
Date: Thu, 08 May 2025 14:01:52 -0700
From: Stephen Boyd <sboyd@...nel.org>
To: André Draszik <andre.draszik@...aro.org>, Gustavo A. R. Silva <gustavoars@...nel.org>, Kees Cook <kees@...nel.org>, Krzysztof Kozlowski <krzk@...nel.org>, Michael Turquette <mturquette@...libre.com>
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: Re: [PATCH] clk: s2mps11: initialise clk_hw_onecell_data::num before accessing ::hws[] in probe()

Quoting André Draszik (2025-03-26 05:08:00)
> 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>
> ---

Applied to clk-fixes