clk: visconti: Add bounds-checking coverage for struct visconti_pll_provider

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 <[e-mail]>
Acked-by: Nobuhiro Iwamatsu <[e-mail]>
Signed-off-by: Gustavo A. R. Silva <[e-mail]>
Link: https://lore.kernel.org/r/e3[e-mail]
Signed-off-by: Stephen Boyd <[e-mail]>

drivers/clk/visconti/pll.c

···
 	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;
 }