RDMA/core: Split port and device counter sysfs attributes

This code creates a 'struct hw_stats_attribute' for each sysfs entry that
contains a naked 'struct attribute' inside.

It then proceeds to attach this same structure to a 'struct device' kobj
and a 'struct ib_port' kobj. However, this violates the typing
requirements.  'struct device' requires the attribute to be a 'struct
device_attribute' and 'struct ib_port' requires the attribute to be
'struct port_attribute'.

This happens to work because the show/store function pointers in all three
structures happen to be at the same offset and happen to be nearly the
same signature. This means when container_of() was used to go between the
wrong two types it still managed to work.

However clang CFI detection notices that the function pointers have a
slightly different signature. As with show/store this was only working
because the device and port struct layouts happened to have the kobj at
the front.

Correct this by have two independent sets of data structures for the port
and device case. The two different attributes correctly include the
port/device_attribute struct and everything from there up is kept
split. The show/store function call chains start with device/port unique
functions that invoke a common show/store function pointer.

Link: https://lore.kernel.org/r/a8b3864b4e722aed3657512af6aa47dc3c5033be.1623427137.git.leonro@nvidia.comReported-by: Nathan Chancellor <nathan@kernel.org>
Tested-by: Nathan Chancellor <nathan@kernel.org>
Cc: Kees Cook <keescook@chromium.org>
Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>

include/rdma/ib_verbs.h

@@ -51,6 +51,7 @@ struct ib_usrq_object;
 struct ib_uwq_object;
 struct rdma_cm_id;
 struct ib_port;
+struct hw_stats_device_data;
 
 extern struct workqueue_struct *ib_wq;
 extern struct workqueue_struct *ib_comp_wq;
@@ -2695,8 +2696,7 @@ struct ib_device {
 	u8                           node_type;
 	u32			     phys_port_cnt;
 	struct ib_device_attr        attrs;
-	struct attribute_group	     *hw_stats_ag;
-	struct rdma_hw_stats         *hw_stats;
+	struct hw_stats_device_data *hw_stats_data;
 
 #ifdef CONFIG_CGROUP_RDMA
 	struct rdmacg_device         cg_device;