From: Martin Willi martin@strongswan.org
commit 3a5ca857079ea022e0b1b17fc154f7ad7dbc150f upstream.
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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/net/can/dev.c | 1 + include/net/rtnetlink.h | 2 ++ net/core/dev.c | 2 +- 3 files changed, 4 insertions(+), 1 deletion(-)
--- a/drivers/net/can/dev.c +++ b/drivers/net/can/dev.c @@ -1226,6 +1226,7 @@ static void can_dellink(struct net_devic
static struct rtnl_link_ops can_link_ops __read_mostly = { .kind = "can", + .netns_refund = true, .maxtype = IFLA_CAN_MAX, .policy = can_policy, .setup = can_setup, --- a/include/net/rtnetlink.h +++ b/include/net/rtnetlink.h @@ -33,6 +33,7 @@ static inline int rtnl_msg_family(const * * @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[], --- a/net/core/dev.c +++ b/net/core/dev.c @@ -10121,7 +10121,7 @@ static void __net_exit default_device_ex 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 */