generic: 5.15: qca8k: add kernel version tag on backport patch

[openwrt/staging/svanheule.git] / target / linux / generic / backport-5.15 / 765-v5.17-06-net-next-net-dsa-setup-master-before-ports.patch

diff --git a/target/linux/generic/backport-5.15/765-v5.17-06-net-next-net-dsa-setup-master-before-ports.patch b/target/linux/generic/backport-5.15/765-v5.17-06-net-next-net-dsa-setup-master-before-ports.patch
new file mode 100644 (file)
index 0000000..93cad0c
--- /dev/null
+++ b/target/linux/generic/backport-5.15/765-v5.17-06-net-next-net-dsa-setup-master-before-ports.patch
@@ -0,0 +1,115 @@
+From 11fd667dac315ea3f2469961f6d2869271a46cae Mon Sep 17 00:00:00 2001
+From: Vladimir Oltean <vladimir.oltean@nxp.com>
+Date: Thu, 6 Jan 2022 01:11:17 +0200
+Subject: [PATCH 6/6] net: dsa: setup master before ports
+
+It is said that as soon as a network interface is registered, all its
+resources should have already been prepared, so that it is available for
+sending and receiving traffic. One of the resources needed by a DSA
+slave interface is the master.
+
+dsa_tree_setup
+-> dsa_tree_setup_ports
+   -> dsa_port_setup
+      -> dsa_slave_create
+         -> register_netdevice
+-> dsa_tree_setup_master
+   -> dsa_master_setup
+      -> sets up master->dsa_ptr, which enables reception
+
+Therefore, there is a short period of time after register_netdevice()
+during which the master isn't prepared to pass traffic to the DSA layer
+(master->dsa_ptr is checked by eth_type_trans). Same thing during
+unregistration, there is a time frame in which packets might be missed.
+
+Note that this change opens us to another race: dsa_master_find_slave()
+will get invoked potentially earlier than the slave creation, and later
+than the slave deletion. Since dp->slave starts off as a NULL pointer,
+the earlier calls aren't a problem, but the later calls are. To avoid
+use-after-free, we should zeroize dp->slave before calling
+dsa_slave_destroy().
+
+In practice I cannot really test real life improvements brought by this
+change, since in my systems, netdevice creation races with PHY autoneg
+which takes a few seconds to complete, and that masks quite a few races.
+Effects might be noticeable in a setup with fixed links all the way to
+an external system.
+
+Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
+Signed-off-by: David S. Miller <davem@davemloft.net>
+---
+ net/dsa/dsa2.c | 23 +++++++++++++----------
+ 1 file changed, 13 insertions(+), 10 deletions(-)
+
+--- a/net/dsa/dsa2.c
++++ b/net/dsa/dsa2.c
+@@ -545,6 +545,7 @@ static void dsa_port_teardown(struct dsa
+       struct devlink_port *dlp = &dp->devlink_port;
+       struct dsa_switch *ds = dp->ds;
+       struct dsa_mac_addr *a, *tmp;
++      struct net_device *slave;
+ 
+       if (!dp->setup)
+               return;
+@@ -566,9 +567,11 @@ static void dsa_port_teardown(struct dsa
+               dsa_port_link_unregister_of(dp);
+               break;
+       case DSA_PORT_TYPE_USER:
+-              if (dp->slave) {
+-                      dsa_slave_destroy(dp->slave);
++              slave = dp->slave;
++
++              if (slave) {
+                       dp->slave = NULL;
++                      dsa_slave_destroy(slave);
+               }
+               break;
+       }
+@@ -1130,17 +1133,17 @@ static int dsa_tree_setup(struct dsa_swi
+       if (err)
+               goto teardown_cpu_ports;
+ 
+-      err = dsa_tree_setup_ports(dst);
++      err = dsa_tree_setup_master(dst);
+       if (err)
+               goto teardown_switches;
+ 
+-      err = dsa_tree_setup_master(dst);
++      err = dsa_tree_setup_ports(dst);
+       if (err)
+-              goto teardown_ports;
++              goto teardown_master;
+ 
+       err = dsa_tree_setup_lags(dst);
+       if (err)
+-              goto teardown_master;
++              goto teardown_ports;
+ 
+       dst->setup = true;
+ 
+@@ -1148,10 +1151,10 @@ static int dsa_tree_setup(struct dsa_swi
+ 
+       return 0;
+ 
+-teardown_master:
+-      dsa_tree_teardown_master(dst);
+ teardown_ports:
+       dsa_tree_teardown_ports(dst);
++teardown_master:
++      dsa_tree_teardown_master(dst);
+ teardown_switches:
+       dsa_tree_teardown_switches(dst);
+ teardown_cpu_ports:
+@@ -1169,10 +1172,10 @@ static void dsa_tree_teardown(struct dsa
+ 
+       dsa_tree_teardown_lags(dst);
+ 
+-      dsa_tree_teardown_master(dst);
+-
+       dsa_tree_teardown_ports(dst);
+ 
++      dsa_tree_teardown_master(dst);
++
+       dsa_tree_teardown_switches(dst);
+ 
+       dsa_tree_teardown_cpu_ports(dst);