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Subject[PATCH 5.10 08/57] net: switchdev: dont set port_obj_info->handled true when -EOPNOTSUPP
Date
From: Rasmus Villemoes <rasmus.villemoes@prevas.dk>

commit 20776b465c0c249f5e5b5b4fe077cd24ef1cda86 upstream.

It's not true that switchdev_port_obj_notify() only inspects the
->handled field of "struct switchdev_notifier_port_obj_info" if
call_switchdev_blocking_notifiers() returns 0 - there's a WARN_ON()
triggering for a non-zero return combined with ->handled not being
true. But the real problem here is that -EOPNOTSUPP is not being
properly handled.

The wrapper functions switchdev_handle_port_obj_add() et al change a
return value of -EOPNOTSUPP to 0, and the treatment of ->handled in
switchdev_port_obj_notify() seems to be designed to change that back
to -EOPNOTSUPP in case nobody actually acted on the notifier (i.e.,
everybody returned -EOPNOTSUPP).

Currently, as soon as some device down the stack passes the check_cb()
check, ->handled gets set to true, which means that
switchdev_port_obj_notify() cannot actually ever return -EOPNOTSUPP.

This, for example, means that the detection of hardware offload
support in the MRP code is broken: switchdev_port_obj_add() used by
br_mrp_switchdev_send_ring_test() always returns 0, so since the MRP
code thinks the generation of MRP test frames has been offloaded, no
such frames are actually put on the wire. Similarly,
br_mrp_switchdev_set_ring_role() also always returns 0, causing
mrp->ring_role_offloaded to be set to 1.

To fix this, continue to set ->handled true if any callback returns
success or any error distinct from -EOPNOTSUPP. But if all the
callbacks return -EOPNOTSUPP, make sure that ->handled stays false, so
the logic in switchdev_port_obj_notify() can propagate that
information.

Fixes: 9a9f26e8f7ea ("bridge: mrp: Connect MRP API with the switchdev API")
Fixes: f30f0601eb93 ("switchdev: Add helpers to aid traversal through lower devices")
Reviewed-by: Petr Machata <petrm@nvidia.com>
Signed-off-by: Rasmus Villemoes <rasmus.villemoes@prevas.dk>
Link: https://lore.kernel.org/r/20210125124116.102928-1-rasmus.villemoes@prevas.dk
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/switchdev/switchdev.c | 23 +++++++++++++----------
1 file changed, 13 insertions(+), 10 deletions(-)

--- a/net/switchdev/switchdev.c
+++ b/net/switchdev/switchdev.c
@@ -460,10 +460,11 @@ static int __switchdev_handle_port_obj_a
extack = switchdev_notifier_info_to_extack(&port_obj_info->info);

if (check_cb(dev)) {
- /* This flag is only checked if the return value is success. */
- port_obj_info->handled = true;
- return add_cb(dev, port_obj_info->obj, port_obj_info->trans,
- extack);
+ err = add_cb(dev, port_obj_info->obj, port_obj_info->trans,
+ extack);
+ if (err != -EOPNOTSUPP)
+ port_obj_info->handled = true;
+ return err;
}

/* Switch ports might be stacked under e.g. a LAG. Ignore the
@@ -515,9 +516,10 @@ static int __switchdev_handle_port_obj_d
int err = -EOPNOTSUPP;

if (check_cb(dev)) {
- /* This flag is only checked if the return value is success. */
- port_obj_info->handled = true;
- return del_cb(dev, port_obj_info->obj);
+ err = del_cb(dev, port_obj_info->obj);
+ if (err != -EOPNOTSUPP)
+ port_obj_info->handled = true;
+ return err;
}

/* Switch ports might be stacked under e.g. a LAG. Ignore the
@@ -568,9 +570,10 @@ static int __switchdev_handle_port_attr_
int err = -EOPNOTSUPP;

if (check_cb(dev)) {
- port_attr_info->handled = true;
- return set_cb(dev, port_attr_info->attr,
- port_attr_info->trans);
+ err = set_cb(dev, port_attr_info->attr, port_attr_info->trans);
+ if (err != -EOPNOTSUPP)
+ port_attr_info->handled = true;
+ return err;
}

/* Switch ports might be stacked under e.g. a LAG. Ignore the

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