mailbox: zynqmp: Annotate struct zynqmp_ipi_pdata with __counted_by

Prepare for the coming implementation by GCC and Clang of the __counted_by
attribute. Flexible array members annotated with __counted_by can have
their accesses bounds-checked at run-time checking via CONFIG_UBSAN_BOUNDS
(for array indexing) and CONFIG_FORTIFY_SOURCE (for strcpy/memcpy-family
functions).

As found with Coccinelle[1], add __counted_by for struct zynqmp_ipi_pdata.

[1] https://github.com/kees/kernel-tools/blob/trunk/coccinelle/examples/counted_by.cocci

Cc: Jassi Brar <[email protected]>
Cc: Michal Simek <[email protected]>
Cc: [email protected]
Reviewed-by: Justin Stitt <[email protected]>
Reviewed-by: "Gustavo A. R. Silva" <[email protected]>
Acked-by: Michal Simek <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Kees Cook <[email protected]>

Author: kees

drivers/mailbox/zynqmp-ipi-mailbox.c

@@ -108,7 +108,7 @@ struct zynqmp_ipi_pdata {
 	unsigned int method;
 	u32 local_id;
 	int num_mboxes;
-	struct zynqmp_ipi_mbox ipi_mboxes[];
+	struct zynqmp_ipi_mbox ipi_mboxes[] __counted_by(num_mboxes);
 };
 
 static struct device_driver zynqmp_ipi_mbox_driver = {