276 lines
11 KiB
Diff
276 lines
11 KiB
Diff
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From: Linus Lüssing <linus.luessing@c0d3.blue>
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Date: Mon, 25 Jan 2021 01:38:19 +0100
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Subject: kernel: bridge: Fix a deadlock when enabling multicast snooping
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[ Upstream commit 851d0a73c90e6c8c63fef106c6c1e73df7e05d9d ]
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From: Joseph Huang <Joseph.Huang@garmin.com>
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When enabling multicast snooping, bridge module deadlocks on multicast_lock
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if 1) IPv6 is enabled, and 2) there is an existing querier on the same L2
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network.
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The deadlock was caused by the following sequence: While holding the lock,
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br_multicast_open calls br_multicast_join_snoopers, which eventually causes
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IP stack to (attempt to) send out a Listener Report (in igmp6_join_group).
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Since the destination Ethernet address is a multicast address, br_dev_xmit
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feeds the packet back to the bridge via br_multicast_rcv, which in turn
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calls br_multicast_add_group, which then deadlocks on multicast_lock.
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The fix is to move the call br_multicast_join_snoopers outside of the
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critical section. This works since br_multicast_join_snoopers only deals
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with IP and does not modify any multicast data structures of the bridge,
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so there's no need to hold the lock.
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Steps to reproduce:
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1. sysctl net.ipv6.conf.all.force_mld_version=1
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2. have another querier
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3. ip link set dev bridge type bridge mcast_snooping 0 && \
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ip link set dev bridge type bridge mcast_snooping 1 < deadlock >
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A typical call trace looks like the following:
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[ 936.251495] _raw_spin_lock+0x5c/0x68
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[ 936.255221] br_multicast_add_group+0x40/0x170 [bridge]
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[ 936.260491] br_multicast_rcv+0x7ac/0xe30 [bridge]
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[ 936.265322] br_dev_xmit+0x140/0x368 [bridge]
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[ 936.269689] dev_hard_start_xmit+0x94/0x158
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[ 936.273876] __dev_queue_xmit+0x5ac/0x7f8
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[ 936.277890] dev_queue_xmit+0x10/0x18
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[ 936.281563] neigh_resolve_output+0xec/0x198
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[ 936.285845] ip6_finish_output2+0x240/0x710
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[ 936.290039] __ip6_finish_output+0x130/0x170
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[ 936.294318] ip6_output+0x6c/0x1c8
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[ 936.297731] NF_HOOK.constprop.0+0xd8/0xe8
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[ 936.301834] igmp6_send+0x358/0x558
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[ 936.305326] igmp6_join_group.part.0+0x30/0xf0
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[ 936.309774] igmp6_group_added+0xfc/0x110
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[ 936.313787] __ipv6_dev_mc_inc+0x1a4/0x290
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[ 936.317885] ipv6_dev_mc_inc+0x10/0x18
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[ 936.321677] br_multicast_open+0xbc/0x110 [bridge]
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[ 936.326506] br_multicast_toggle+0xec/0x140 [bridge]
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Fixes: 4effd28c1245 ("bridge: join all-snoopers multicast address")
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Signed-off-by: Joseph Huang <Joseph.Huang@garmin.com>
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Acked-by: Nikolay Aleksandrov <nikolay@nvidia.com>
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Link: https://lore.kernel.org/r/20201204235628.50653-1-Joseph.Huang@garmin.com
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Signed-off-by: Jakub Kicinski <kuba@kernel.org>
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Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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[linus.luessing@c0d3.blue: backported to 4.4]
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diff --git a/target/linux/generic/backport-4.14/120-bridge-Fix-a-deadlock-when-enabling-multicast-snoopi.patch b/target/linux/generic/backport-4.14/120-bridge-Fix-a-deadlock-when-enabling-multicast-snoopi.patch
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new file mode 100644
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index 0000000000000000000000000000000000000000..e89d9e3eb2063b1f478c0217aaa3c89d14880043
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--- /dev/null
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+++ b/target/linux/generic/backport-4.14/120-bridge-Fix-a-deadlock-when-enabling-multicast-snoopi.patch
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@@ -0,0 +1,209 @@
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+From 0e125bd346d3b9d6997e525b263834f6b650cf60 Mon Sep 17 00:00:00 2001
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+From: Joseph Huang <Joseph.Huang@garmin.com>
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+Date: Fri, 4 Dec 2020 18:56:28 -0500
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+Subject: [PATCH] bridge: Fix a deadlock when enabling multicast snooping
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+
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+[ Upstream commit 851d0a73c90e6c8c63fef106c6c1e73df7e05d9d ]
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+
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+When enabling multicast snooping, bridge module deadlocks on multicast_lock
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+if 1) IPv6 is enabled, and 2) there is an existing querier on the same L2
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+network.
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+
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+The deadlock was caused by the following sequence: While holding the lock,
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+br_multicast_open calls br_multicast_join_snoopers, which eventually causes
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+IP stack to (attempt to) send out a Listener Report (in igmp6_join_group).
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+Since the destination Ethernet address is a multicast address, br_dev_xmit
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+feeds the packet back to the bridge via br_multicast_rcv, which in turn
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+calls br_multicast_add_group, which then deadlocks on multicast_lock.
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+
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+The fix is to move the call br_multicast_join_snoopers outside of the
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+critical section. This works since br_multicast_join_snoopers only deals
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+with IP and does not modify any multicast data structures of the bridge,
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+so there's no need to hold the lock.
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+
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+Steps to reproduce:
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+1. sysctl net.ipv6.conf.all.force_mld_version=1
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+2. have another querier
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+3. ip link set dev bridge type bridge mcast_snooping 0 && \
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+ ip link set dev bridge type bridge mcast_snooping 1 < deadlock >
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+
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+A typical call trace looks like the following:
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+
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+[ 936.251495] _raw_spin_lock+0x5c/0x68
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+[ 936.255221] br_multicast_add_group+0x40/0x170 [bridge]
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+[ 936.260491] br_multicast_rcv+0x7ac/0xe30 [bridge]
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+[ 936.265322] br_dev_xmit+0x140/0x368 [bridge]
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+[ 936.269689] dev_hard_start_xmit+0x94/0x158
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+[ 936.273876] __dev_queue_xmit+0x5ac/0x7f8
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+[ 936.277890] dev_queue_xmit+0x10/0x18
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+[ 936.281563] neigh_resolve_output+0xec/0x198
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+[ 936.285845] ip6_finish_output2+0x240/0x710
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+[ 936.290039] __ip6_finish_output+0x130/0x170
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+[ 936.294318] ip6_output+0x6c/0x1c8
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+[ 936.297731] NF_HOOK.constprop.0+0xd8/0xe8
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+[ 936.301834] igmp6_send+0x358/0x558
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+[ 936.305326] igmp6_join_group.part.0+0x30/0xf0
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+[ 936.309774] igmp6_group_added+0xfc/0x110
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+[ 936.313787] __ipv6_dev_mc_inc+0x1a4/0x290
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+[ 936.317885] ipv6_dev_mc_inc+0x10/0x18
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+[ 936.321677] br_multicast_open+0xbc/0x110 [bridge]
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+[ 936.326506] br_multicast_toggle+0xec/0x140 [bridge]
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+
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+Fixes: 4effd28c1245 ("bridge: join all-snoopers multicast address")
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+Signed-off-by: Joseph Huang <Joseph.Huang@garmin.com>
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+Acked-by: Nikolay Aleksandrov <nikolay@nvidia.com>
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+Link: https://lore.kernel.org/r/20201204235628.50653-1-Joseph.Huang@garmin.com
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+Signed-off-by: Jakub Kicinski <kuba@kernel.org>
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+Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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+[linus.luessing@c0d3.blue: backported to 4.4]
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+---
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+ net/bridge/br_device.c | 6 ++++++
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+ net/bridge/br_multicast.c | 34 +++++++++++++++++++++++++---------
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+ net/bridge/br_private.h | 10 ++++++++++
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+ 3 files changed, 41 insertions(+), 9 deletions(-)
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+
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+diff --git a/net/bridge/br_device.c b/net/bridge/br_device.c
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+index b7cc322acdc8..4bd8a7ba002a 100644
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+--- a/net/bridge/br_device.c
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++++ b/net/bridge/br_device.c
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+@@ -140,6 +140,9 @@ static int br_dev_open(struct net_device *dev)
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+ br_stp_enable_bridge(br);
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+ br_multicast_open(br);
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+
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++ if (!br->multicast_disabled)
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++ br_multicast_join_snoopers(br);
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++
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+ return 0;
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+ }
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+
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+@@ -160,6 +163,9 @@ static int br_dev_stop(struct net_device *dev)
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+ br_stp_disable_bridge(br);
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+ br_multicast_stop(br);
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+
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++ if (!br->multicast_disabled)
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++ br_multicast_leave_snoopers(br);
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++
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+ netif_stop_queue(dev);
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+
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+ return 0;
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+diff --git a/net/bridge/br_multicast.c b/net/bridge/br_multicast.c
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+index 6d8d1cf2ddc6..1b1d06549583 100644
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+--- a/net/bridge/br_multicast.c
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++++ b/net/bridge/br_multicast.c
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+@@ -2314,7 +2314,7 @@ static inline void br_ip6_multicast_join_snoopers(struct net_bridge *br)
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+ }
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+ #endif
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+
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+-static void br_multicast_join_snoopers(struct net_bridge *br)
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++void br_multicast_join_snoopers(struct net_bridge *br)
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+ {
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+ br_ip4_multicast_join_snoopers(br);
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+ br_ip6_multicast_join_snoopers(br);
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+@@ -2345,7 +2345,7 @@ static inline void br_ip6_multicast_leave_snoopers(struct net_bridge *br)
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+ }
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+ #endif
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+
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+-static void br_multicast_leave_snoopers(struct net_bridge *br)
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++void br_multicast_leave_snoopers(struct net_bridge *br)
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+ {
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+ br_ip4_multicast_leave_snoopers(br);
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+ br_ip6_multicast_leave_snoopers(br);
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+@@ -2364,9 +2364,6 @@ static void __br_multicast_open(struct net_bridge *br,
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+
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+ void br_multicast_open(struct net_bridge *br)
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+ {
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+- if (!br->multicast_disabled)
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+- br_multicast_join_snoopers(br);
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+-
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+ __br_multicast_open(br, &br->ip4_own_query);
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+ #if IS_ENABLED(CONFIG_IPV6)
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+ __br_multicast_open(br, &br->ip6_own_query);
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+@@ -2382,9 +2379,6 @@ void br_multicast_stop(struct net_bridge *br)
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+ del_timer_sync(&br->ip6_other_query.timer);
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+ del_timer_sync(&br->ip6_own_query.timer);
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+ #endif
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+-
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+- if (!br->multicast_disabled)
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+- br_multicast_leave_snoopers(br);
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+ }
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+
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+ void br_multicast_dev_del(struct net_bridge *br)
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+@@ -2540,6 +2534,7 @@ int br_multicast_toggle(struct net_bridge *br, unsigned long val)
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+ {
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+ struct net_bridge_mdb_htable *mdb;
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+ struct net_bridge_port *port;
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++ bool change_snoopers = false;
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+ int err = 0;
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+
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+ spin_lock_bh(&br->multicast_lock);
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+@@ -2549,7 +2544,7 @@ int br_multicast_toggle(struct net_bridge *br, unsigned long val)
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+ br_mc_disabled_update(br->dev, !val);
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+ br->multicast_disabled = !val;
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+ if (br->multicast_disabled) {
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+- br_multicast_leave_snoopers(br);
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++ change_snoopers = true;
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+ goto unlock;
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+ }
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+
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+@@ -2575,9 +2570,30 @@ int br_multicast_toggle(struct net_bridge *br, unsigned long val)
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+ list_for_each_entry(port, &br->port_list, list)
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+ __br_multicast_enable_port(port);
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+
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++ change_snoopers = true;
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++
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+ unlock:
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+ spin_unlock_bh(&br->multicast_lock);
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+
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++ /* br_multicast_join_snoopers has the potential to cause
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++ * an MLD Report/Leave to be delivered to br_multicast_rcv,
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++ * which would in turn call br_multicast_add_group, which would
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++ * attempt to acquire multicast_lock. This function should be
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++ * called after the lock has been released to avoid deadlocks on
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++ * multicast_lock.
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++ *
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++ * br_multicast_leave_snoopers does not have the problem since
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++ * br_multicast_rcv first checks BROPT_MULTICAST_ENABLED, and
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++ * returns without calling br_multicast_ipv4/6_rcv if it's not
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++ * enabled. Moved both functions out just for symmetry.
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++ */
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++ if (change_snoopers) {
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++ if (!br->multicast_disabled)
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++ br_multicast_join_snoopers(br);
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++ else
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++ br_multicast_leave_snoopers(br);
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++ }
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++
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+ return err;
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+ }
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+
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+diff --git a/net/bridge/br_private.h b/net/bridge/br_private.h
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+index bbf7513c1d16..cb701c31199d 100644
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+--- a/net/bridge/br_private.h
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++++ b/net/bridge/br_private.h
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+@@ -611,6 +611,8 @@ void br_multicast_del_port(struct net_bridge_port *port);
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+ void br_multicast_enable_port(struct net_bridge_port *port);
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+ void br_multicast_disable_port(struct net_bridge_port *port);
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+ void br_multicast_init(struct net_bridge *br);
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++void br_multicast_join_snoopers(struct net_bridge *br);
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++void br_multicast_leave_snoopers(struct net_bridge *br);
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+ void br_multicast_open(struct net_bridge *br);
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+ void br_multicast_stop(struct net_bridge *br);
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+ void br_multicast_dev_del(struct net_bridge *br);
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+@@ -736,6 +738,14 @@ static inline void br_multicast_init(struct net_bridge *br)
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+ {
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+ }
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+
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++static inline void br_multicast_join_snoopers(struct net_bridge *br)
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++{
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++}
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++
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++static inline void br_multicast_leave_snoopers(struct net_bridge *br)
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++{
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++}
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++
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+ static inline void br_multicast_open(struct net_bridge *br)
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+ {
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+ }
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+--
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+2.29.2
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+
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