Messages in this thread | | | Date | Wed, 11 Oct 2023 14:41:03 -0700 | From | Kees Cook <> | Subject | Re: [PATCH 2/2][next] clk: socfpga: agilex: Add bounds-checking coverage for struct stratix10_clock_data |
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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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