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Message-ID: <202310120921.3F24CB2E@keescook> Date: Thu, 12 Oct 2023 09:21:50 -0700 From: Kees Cook <keescook@...omium.org> To: "Gustavo A. R. Silva" <gustavoars@...nel.org> Cc: Michael Turquette <mturquette@...libre.com>, Stephen Boyd <sboyd@...nel.org>, Nobuhiro Iwamatsu <nobuhiro1.iwamatsu@...hiba.co.jp>, linux-clk@...r.kernel.org, linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org Subject: Re: [PATCH 2/2][next] clk: visconti: Add bounds-checking coverage for struct visconti_pll_provider On Wed, Oct 11, 2023 at 08:18:45PM -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 particular case `num`, > is updated before the first access to the flex-array member, in this > particular case array `hws`. See below: > > 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 visconti_pll_provider`: > > drivers/clk/visconti/pll.h: > 16 struct visconti_pll_provider { > 17 void __iomem *reg_base; > 18 struct device_node *node; > 19 > 20 /* Must be last */ > 21 struct clk_hw_onecell_data clk_data; > 22 }; > > Hence, we need to move the assignments to `ctx->clk_data.num` after > allocation for `struct visconti_pll_provider` and before accessing the > flexible array `ctx->clk_data.hws`. And, as assignments for all members > in `struct visconti_pll_provider` are originally adjacent to each other, > relocate all assignments together, so we don't split up > `ctx->clk_data.hws = nr_plls` from the rest. :) > > Signed-off-by: Gustavo A. R. Silva <gustavoars@...nel.org> Looks good; thanks! Reviewed-by: Kees Cook <keescook@...omium.org> -- Kees Cook
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