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SubjectRe: [PATCH 2/2][next] clk: socfpga: agilex: Add bounds-checking coverage for struct stratix10_clock_data
On Wed, Oct 11, 2023 at 03:35:26PM -0600, Gustavo A. R. Silva wrote:
> In order to gain the bounds-checking coverage that __counted_by provides
> to flexible-array members at run-time via CONFIG_UBSAN_BOUNDS (for array
> indexing) and CONFIG_FORTIFY_SOURCE (for strcpy/memcpy-family functions),
> we must make sure that the counter member, in this case `num`, is updated
> before the first access to the flex-array member, in this case array `hws`.
>
> commit f316cdff8d67 ("clk: Annotate struct clk_hw_onecell_data with
> __counted_by") introduced `__counted_by` for `struct clk_hw_onecell_data`
> together with changes to relocate some of assignments of counter `num`
> before `hws` is accessed:
>
> include/linux/clk-provider.h:
> 1380 struct clk_hw_onecell_data {
> 1381 unsigned int num;
> 1382 struct clk_hw *hws[] __counted_by(num);
> 1383 };
>
> However, this structure is used as a member in other structs, in this
> case in `struct sstratix10_clock_data`:
>
> drivers/clk/socfpga/stratix10-clk.h:
> 9 struct stratix10_clock_data {
> 10 void __iomem *base;
> 11
> 12 /* Must be last */
> 13 struct clk_hw_onecell_data clk_data;
> 14 };
>
> Hence, we need to move the assignments to `clk_data->clk_data.num` after
> allocations for `struct stratix10_clock_data` and before accessing the
> flexible array `clk_data->clk_data.hws`. And, as assignments for both
> `clk_data->clk_data.num` and `clk_data->base` are originally adjacent to
> each other, relocate both assignments together.
>
> Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>

Yeah, ew. That's super tricky. Nice find.

Reviewed-by: Kees Cook <keescook@chromium.org>

--
Kees Cook

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