| Message ID | e3189f3e40e8723b6d794fb2260e2e9ab6b960bd.1697492890.git.gustavoars@kernel.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | clk: visconti: Fix undefined behavior bug and add bounds-checking coverage | expand |
Quoting Gustavo A. R. Silva (2023-10-16 15:06:16) > 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. :) > > Reviewed-by: Kees Cook <keescook@chromium.org> > Acked-by: Nobuhiro Iwamatsu <nobuhiro1.iwamatsu@toshiba.co.jp> > Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org> > --- Applied to clk-next
diff --git a/drivers/clk/visconti/pll.c b/drivers/clk/visconti/pll.c index 1f3234f22667..e9cd80e085dc 100644 --- a/drivers/clk/visconti/pll.c +++ b/drivers/clk/visconti/pll.c @@ -329,12 +329,12 @@ struct visconti_pll_provider * __init visconti_init_pll(struct device_node *np, if (!ctx) return ERR_PTR(-ENOMEM); - for (i = 0; i < nr_plls; ++i) - ctx->clk_data.hws[i] = ERR_PTR(-ENOENT); - ctx->node = np; ctx->reg_base = base; ctx->clk_data.num = nr_plls; + for (i = 0; i < nr_plls; ++i) + ctx->clk_data.hws[i] = ERR_PTR(-ENOENT); + return ctx; }
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. :) Reviewed-by: Kees Cook <keescook@chromium.org> Acked-by: Nobuhiro Iwamatsu <nobuhiro1.iwamatsu@toshiba.co.jp> Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org> --- Changes in v2: - None. v1: - Link: https://lore.kernel.org/linux-hardening/675633f7ae9893371d35b238f06fd02a3acffebb.1697076650.git.gustavoars@kernel.org/ drivers/clk/visconti/pll.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)