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

[Kees Cook]

On Mon, Nov 24, 2025 at 12:11:06PM -0700, Nathan Chancellor wrote:
> 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@xxxxxxxxxxxxxxx
> Fixes: f316cdff8d67 ("clk: Annotate struct clk_hw_onecell_data with __counted_by")
> Reported-by: Jochen Sprickerhof <jochen@xxxxxxxxxxxxxx>
> Closes: https://lore.kernel.org/aSIYDN5eyKFKoXKL@xxxxxxxxxxx/
> Tested-by: Jochen Sprickerhof <jochen@xxxxxxxxxxxxxx>
> Signed-off-by: Nathan Chancellor <nathan@xxxxxxxxxx>

Reviewed-by: Kees Cook <kees@xxxxxxxxxx>

-- 
Kees Cook