target/linux/generic/backport-5.15/765-v5.17-04-net-next-net-dsa-hold-rtnl_mutex-when-calling-dsa_master_-set.patch

   1 From c146f9bc195a9dc3ad7fd000a14540e7c9df952d Mon Sep 17 00:00:00 2001
   2 From: Vladimir Oltean <vladimir.oltean@nxp.com>
   3 Date: Thu, 6 Jan 2022 01:11:15 +0200
   4 Subject: [PATCH 4/6] net: dsa: hold rtnl_mutex when calling
   5  dsa_master_{setup,teardown}
   6
   7 DSA needs to simulate master tracking events when a binding is first
   8 with a DSA master established and torn down, in order to give drivers
   9 the simplifying guarantee that ->master_state_change calls are made
  10 only when the master's readiness state to pass traffic changes.
  11 master_state_change() provide a operational bool that DSA driver can use
  12 to understand if DSA master is operational or not.
  13 To avoid races, we need to block the reception of
  14 NETDEV_UP/NETDEV_CHANGE/NETDEV_GOING_DOWN events in the netdev notifier
  15 chain while we are changing the master's dev->dsa_ptr (this changes what
  16 netdev_uses_dsa(dev) reports).
  17
  18 The dsa_master_setup() and dsa_master_teardown() functions optionally
  19 require the rtnl_mutex to be held, if the tagger needs the master to be
  20 promiscuous, these functions call dev_set_promiscuity(). Move the
  21 rtnl_lock() from that function and make it top-level.
  22
  23 Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
  24 Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
  25 Signed-off-by: David S. Miller <davem@davemloft.net>
  26 ---
  27  net/dsa/dsa2.c   | 8 ++++++++
  28  net/dsa/master.c | 4 ++--
  29  2 files changed, 10 insertions(+), 2 deletions(-)
  30
  31 --- a/net/dsa/dsa2.c
  32 +++ b/net/dsa/dsa2.c
  33 @@ -1034,6 +1034,8 @@ static int dsa_tree_setup_master(struct
  34         struct dsa_port *dp;
  35         int err;
  36
  37 +       rtnl_lock();
  38 +
  39         list_for_each_entry(dp, &dst->ports, list) {
  40                 if (dsa_port_is_cpu(dp)) {
  41                         err = dsa_master_setup(dp->master, dp);
  42 @@ -1042,6 +1044,8 @@ static int dsa_tree_setup_master(struct
  43                 }
  44         }
  45
  46 +       rtnl_unlock();
  47 +
  48         return 0;
  49  }
  50
  51 @@ -1049,9 +1053,13 @@ static void dsa_tree_teardown_master(str
  52  {
  53         struct dsa_port *dp;
  54
  55 +       rtnl_lock();
  56 +
  57         list_for_each_entry(dp, &dst->ports, list)
  58                 if (dsa_port_is_cpu(dp))
  59                         dsa_master_teardown(dp->master);
  60 +
  61 +       rtnl_unlock();
  62  }
  63
  64  static int dsa_tree_setup_lags(struct dsa_switch_tree *dst)
  65 --- a/net/dsa/master.c
  66 +++ b/net/dsa/master.c
  67 @@ -266,9 +266,9 @@ static void dsa_master_set_promiscuity(s
  68         if (!ops->promisc_on_master)
  69                 return;
  70
  71 -       rtnl_lock();
  72 +       ASSERT_RTNL();
  73 +
  74         dev_set_promiscuity(dev, inc);
  75 -       rtnl_unlock();
  76  }
  77
  78  static ssize_t tagging_show(struct device *d, struct device_attribute *attr,