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ddcebda08b
Add kernel tag that introduced the patch on backport patch. Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>
116 lines
3.4 KiB
Diff
116 lines
3.4 KiB
Diff
From 11fd667dac315ea3f2469961f6d2869271a46cae Mon Sep 17 00:00:00 2001
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From: Vladimir Oltean <vladimir.oltean@nxp.com>
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Date: Thu, 6 Jan 2022 01:11:17 +0200
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Subject: [PATCH 6/6] net: dsa: setup master before ports
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It is said that as soon as a network interface is registered, all its
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resources should have already been prepared, so that it is available for
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sending and receiving traffic. One of the resources needed by a DSA
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slave interface is the master.
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dsa_tree_setup
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-> dsa_tree_setup_ports
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-> dsa_port_setup
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-> dsa_slave_create
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-> register_netdevice
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-> dsa_tree_setup_master
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-> dsa_master_setup
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-> sets up master->dsa_ptr, which enables reception
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Therefore, there is a short period of time after register_netdevice()
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during which the master isn't prepared to pass traffic to the DSA layer
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(master->dsa_ptr is checked by eth_type_trans). Same thing during
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unregistration, there is a time frame in which packets might be missed.
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Note that this change opens us to another race: dsa_master_find_slave()
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will get invoked potentially earlier than the slave creation, and later
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than the slave deletion. Since dp->slave starts off as a NULL pointer,
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the earlier calls aren't a problem, but the later calls are. To avoid
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use-after-free, we should zeroize dp->slave before calling
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dsa_slave_destroy().
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In practice I cannot really test real life improvements brought by this
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change, since in my systems, netdevice creation races with PHY autoneg
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which takes a few seconds to complete, and that masks quite a few races.
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Effects might be noticeable in a setup with fixed links all the way to
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an external system.
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Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
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Signed-off-by: David S. Miller <davem@davemloft.net>
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---
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net/dsa/dsa2.c | 23 +++++++++++++----------
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1 file changed, 13 insertions(+), 10 deletions(-)
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--- a/net/dsa/dsa2.c
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+++ b/net/dsa/dsa2.c
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@@ -545,6 +545,7 @@ static void dsa_port_teardown(struct dsa
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struct devlink_port *dlp = &dp->devlink_port;
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struct dsa_switch *ds = dp->ds;
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struct dsa_mac_addr *a, *tmp;
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+ struct net_device *slave;
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if (!dp->setup)
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return;
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@@ -566,9 +567,11 @@ static void dsa_port_teardown(struct dsa
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dsa_port_link_unregister_of(dp);
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break;
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case DSA_PORT_TYPE_USER:
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- if (dp->slave) {
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- dsa_slave_destroy(dp->slave);
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+ slave = dp->slave;
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+
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+ if (slave) {
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dp->slave = NULL;
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+ dsa_slave_destroy(slave);
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}
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break;
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}
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@@ -1130,17 +1133,17 @@ static int dsa_tree_setup(struct dsa_swi
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if (err)
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goto teardown_cpu_ports;
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- err = dsa_tree_setup_ports(dst);
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+ err = dsa_tree_setup_master(dst);
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if (err)
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goto teardown_switches;
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- err = dsa_tree_setup_master(dst);
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+ err = dsa_tree_setup_ports(dst);
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if (err)
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- goto teardown_ports;
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+ goto teardown_master;
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err = dsa_tree_setup_lags(dst);
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if (err)
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- goto teardown_master;
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+ goto teardown_ports;
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dst->setup = true;
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@@ -1148,10 +1151,10 @@ static int dsa_tree_setup(struct dsa_swi
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return 0;
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-teardown_master:
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- dsa_tree_teardown_master(dst);
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teardown_ports:
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dsa_tree_teardown_ports(dst);
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+teardown_master:
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+ dsa_tree_teardown_master(dst);
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teardown_switches:
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dsa_tree_teardown_switches(dst);
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teardown_cpu_ports:
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@@ -1169,10 +1172,10 @@ static void dsa_tree_teardown(struct dsa
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dsa_tree_teardown_lags(dst);
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- dsa_tree_teardown_master(dst);
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-
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dsa_tree_teardown_ports(dst);
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+ dsa_tree_teardown_master(dst);
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+
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dsa_tree_teardown_switches(dst);
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dsa_tree_teardown_cpu_ports(dst);
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