can: dev: Move device back to init netns on owning netns delete

When a non-initial netns is destroyed, the usual policy is to delete
all virtual network interfaces contained, but move physical interfaces
back to the initial netns. This keeps the physical interface visible
on the system.

CAN devices are somewhat special, as they define rtnl_link_ops even
if they are physical devices. If a CAN interface is moved into a
non-initial netns, destroying that netns lets the interface vanish
instead of moving it back to the initial netns. default_device_exit()
skips CAN interfaces due to having rtnl_link_ops set. Reproducer:

  ip netns add foo
  ip link set can0 netns foo
  ip netns delete foo

WARNING: CPU: 1 PID: 84 at net/core/dev.c:11030 ops_exit_list+0x38/0x60
CPU: 1 PID: 84 Comm: kworker/u4:2 Not tainted 5.10.19 #1
Workqueue: netns cleanup_net
[<c010e700>] (unwind_backtrace) from [<c010a1d8>] (show_stack+0x10/0x14)
[<c010a1d8>] (show_stack) from [<c086dc10>] (dump_stack+0x94/0xa8)
[<c086dc10>] (dump_stack) from [<c086b938>] (__warn+0xb8/0x114)
[<c086b938>] (__warn) from [<c086ba10>] (warn_slowpath_fmt+0x7c/0xac)
[<c086ba10>] (warn_slowpath_fmt) from [<c0629f20>] (ops_exit_list+0x38/0x60)
[<c0629f20>] (ops_exit_list) from [<c062a5c4>] (cleanup_net+0x230/0x380)
[<c062a5c4>] (cleanup_net) from [<c0142c20>] (process_one_work+0x1d8/0x438)
[<c0142c20>] (process_one_work) from [<c0142ee4>] (worker_thread+0x64/0x5a8)
[<c0142ee4>] (worker_thread) from [<c0148a98>] (kthread+0x148/0x14c)
[<c0148a98>] (kthread) from [<c0100148>] (ret_from_fork+0x14/0x2c)

To properly restore physical CAN devices to the initial netns on owning
netns exit, introduce a flag on rtnl_link_ops that can be set by drivers.
For CAN devices setting this flag, default_device_exit() considers them
non-virtual, applying the usual namespace move.

The issue was introduced in the commit mentioned below, as at that time
CAN devices did not have a dellink() operation.

Fixes: e008b5fc8dc7 ("net: Simplfy default_device_exit and improve batching.")
Link: https://lore.kernel.org/r/20210302122423.872326-1-martin@strongswan.org
Signed-off-by: Martin Willi <martin@strongswan.org>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

diff --git a/drivers/net/can/dev/netlink.c b/drivers/net/can/dev/netlink.c
index 867f6be31230b7723ab9b9c1aa42e2a6a2d40b2b..f5d79e6e548387254f51ab58d187e04c9d28141a 100644 (file)
--- a/drivers/net/can/dev/netlink.c
+++ b/drivers/net/can/dev/netlink.c
@@ -355,6 +355,7 @@ static void can_dellink(struct net_device *dev, struct list_head *head)
 
 struct rtnl_link_ops can_link_ops __read_mostly = {
        .kind           = "can",
+       .netns_refund   = true,
        .maxtype        = IFLA_CAN_MAX,
        .policy         = can_policy,
        .setup          = can_setup,

diff --git a/include/net/rtnetlink.h b/include/net/rtnetlink.h
index e2091bb2b3a8e72715d83f5b1c36304a026b4330..4da61c950e931a424d60c6af5b7400e80d6bb904 100644 (file)
--- a/include/net/rtnetlink.h
+++ b/include/net/rtnetlink.h
@@ -33,6 +33,7 @@ static inline int rtnl_msg_family(const struct nlmsghdr *nlh)
  *
  *     @list: Used internally
  *     @kind: Identifier
+ *     @netns_refund: Physical device, move to init_net on netns exit
  *     @maxtype: Highest device specific netlink attribute number
  *     @policy: Netlink policy for device specific attribute validation
  *     @validate: Optional validation function for netlink/changelink parameters
@@ -64,6 +65,7 @@ struct rtnl_link_ops {
        size_t                  priv_size;
        void                    (*setup)(struct net_device *dev);
 
+       bool                    netns_refund;
        unsigned int            maxtype;
        const struct nla_policy *policy;
        int                     (*validate)(struct nlattr *tb[],

diff --git a/net/core/dev.c b/net/core/dev.c
index 6c5967e801328a00ffb434a430a865ddcf8c02db..a142a207fc1d5663f9a75094d328a1db3c1b25c9 100644 (file)
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -11346,7 +11346,7 @@ static void __net_exit default_device_exit(struct net *net)
                        continue;
 
                /* Leave virtual devices for the generic cleanup */
-               if (dev->rtnl_link_ops)
+               if (dev->rtnl_link_ops && !dev->rtnl_link_ops->netns_refund)
                        continue;
 
                /* Push remaining network devices to init_net */