lkml.org 
[lkml]   [2020]   [Dec]   [19]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    From
    Subject[PATCH 5.4 09/34] bridge: Fix a deadlock when enabling multicast snooping
    Date
    From: Joseph Huang <Joseph.Huang@garmin.com>

    [ Upstream commit 851d0a73c90e6c8c63fef106c6c1e73df7e05d9d ]

    When enabling multicast snooping, bridge module deadlocks on multicast_lock
    if 1) IPv6 is enabled, and 2) there is an existing querier on the same L2
    network.

    The deadlock was caused by the following sequence: While holding the lock,
    br_multicast_open calls br_multicast_join_snoopers, which eventually causes
    IP stack to (attempt to) send out a Listener Report (in igmp6_join_group).
    Since the destination Ethernet address is a multicast address, br_dev_xmit
    feeds the packet back to the bridge via br_multicast_rcv, which in turn
    calls br_multicast_add_group, which then deadlocks on multicast_lock.

    The fix is to move the call br_multicast_join_snoopers outside of the
    critical section. This works since br_multicast_join_snoopers only deals
    with IP and does not modify any multicast data structures of the bridge,
    so there's no need to hold the lock.

    Steps to reproduce:
    1. sysctl net.ipv6.conf.all.force_mld_version=1
    2. have another querier
    3. ip link set dev bridge type bridge mcast_snooping 0 && \
    ip link set dev bridge type bridge mcast_snooping 1 < deadlock >

    A typical call trace looks like the following:

    [ 936.251495] _raw_spin_lock+0x5c/0x68
    [ 936.255221] br_multicast_add_group+0x40/0x170 [bridge]
    [ 936.260491] br_multicast_rcv+0x7ac/0xe30 [bridge]
    [ 936.265322] br_dev_xmit+0x140/0x368 [bridge]
    [ 936.269689] dev_hard_start_xmit+0x94/0x158
    [ 936.273876] __dev_queue_xmit+0x5ac/0x7f8
    [ 936.277890] dev_queue_xmit+0x10/0x18
    [ 936.281563] neigh_resolve_output+0xec/0x198
    [ 936.285845] ip6_finish_output2+0x240/0x710
    [ 936.290039] __ip6_finish_output+0x130/0x170
    [ 936.294318] ip6_output+0x6c/0x1c8
    [ 936.297731] NF_HOOK.constprop.0+0xd8/0xe8
    [ 936.301834] igmp6_send+0x358/0x558
    [ 936.305326] igmp6_join_group.part.0+0x30/0xf0
    [ 936.309774] igmp6_group_added+0xfc/0x110
    [ 936.313787] __ipv6_dev_mc_inc+0x1a4/0x290
    [ 936.317885] ipv6_dev_mc_inc+0x10/0x18
    [ 936.321677] br_multicast_open+0xbc/0x110 [bridge]
    [ 936.326506] br_multicast_toggle+0xec/0x140 [bridge]

    Fixes: 4effd28c1245 ("bridge: join all-snoopers multicast address")
    Signed-off-by: Joseph Huang <Joseph.Huang@garmin.com>
    Acked-by: Nikolay Aleksandrov <nikolay@nvidia.com>
    Link: https://lore.kernel.org/r/20201204235628.50653-1-Joseph.Huang@garmin.com
    Signed-off-by: Jakub Kicinski <kuba@kernel.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    net/bridge/br_device.c | 6 ++++++
    net/bridge/br_multicast.c | 34 +++++++++++++++++++++++++---------
    net/bridge/br_private.h | 10 ++++++++++
    3 files changed, 41 insertions(+), 9 deletions(-)

    --- a/net/bridge/br_device.c
    +++ b/net/bridge/br_device.c
    @@ -168,6 +168,9 @@ static int br_dev_open(struct net_device
    br_stp_enable_bridge(br);
    br_multicast_open(br);

    + if (br_opt_get(br, BROPT_MULTICAST_ENABLED))
    + br_multicast_join_snoopers(br);
    +
    return 0;
    }

    @@ -188,6 +191,9 @@ static int br_dev_stop(struct net_device
    br_stp_disable_bridge(br);
    br_multicast_stop(br);

    + if (br_opt_get(br, BROPT_MULTICAST_ENABLED))
    + br_multicast_leave_snoopers(br);
    +
    netif_stop_queue(dev);

    return 0;
    --- a/net/bridge/br_multicast.c
    +++ b/net/bridge/br_multicast.c
    @@ -1848,7 +1848,7 @@ static inline void br_ip6_multicast_join
    }
    #endif

    -static void br_multicast_join_snoopers(struct net_bridge *br)
    +void br_multicast_join_snoopers(struct net_bridge *br)
    {
    br_ip4_multicast_join_snoopers(br);
    br_ip6_multicast_join_snoopers(br);
    @@ -1879,7 +1879,7 @@ static inline void br_ip6_multicast_leav
    }
    #endif

    -static void br_multicast_leave_snoopers(struct net_bridge *br)
    +void br_multicast_leave_snoopers(struct net_bridge *br)
    {
    br_ip4_multicast_leave_snoopers(br);
    br_ip6_multicast_leave_snoopers(br);
    @@ -1898,9 +1898,6 @@ static void __br_multicast_open(struct n

    void br_multicast_open(struct net_bridge *br)
    {
    - if (br_opt_get(br, BROPT_MULTICAST_ENABLED))
    - br_multicast_join_snoopers(br);
    -
    __br_multicast_open(br, &br->ip4_own_query);
    #if IS_ENABLED(CONFIG_IPV6)
    __br_multicast_open(br, &br->ip6_own_query);
    @@ -1916,9 +1913,6 @@ void br_multicast_stop(struct net_bridge
    del_timer_sync(&br->ip6_other_query.timer);
    del_timer_sync(&br->ip6_own_query.timer);
    #endif
    -
    - if (br_opt_get(br, BROPT_MULTICAST_ENABLED))
    - br_multicast_leave_snoopers(br);
    }

    void br_multicast_dev_del(struct net_bridge *br)
    @@ -2049,6 +2043,7 @@ static void br_multicast_start_querier(s
    int br_multicast_toggle(struct net_bridge *br, unsigned long val)
    {
    struct net_bridge_port *port;
    + bool change_snoopers = false;

    spin_lock_bh(&br->multicast_lock);
    if (!!br_opt_get(br, BROPT_MULTICAST_ENABLED) == !!val)
    @@ -2057,7 +2052,7 @@ int br_multicast_toggle(struct net_bridg
    br_mc_disabled_update(br->dev, val);
    br_opt_toggle(br, BROPT_MULTICAST_ENABLED, !!val);
    if (!br_opt_get(br, BROPT_MULTICAST_ENABLED)) {
    - br_multicast_leave_snoopers(br);
    + change_snoopers = true;
    goto unlock;
    }

    @@ -2068,9 +2063,30 @@ int br_multicast_toggle(struct net_bridg
    list_for_each_entry(port, &br->port_list, list)
    __br_multicast_enable_port(port);

    + change_snoopers = true;
    +
    unlock:
    spin_unlock_bh(&br->multicast_lock);

    + /* br_multicast_join_snoopers has the potential to cause
    + * an MLD Report/Leave to be delivered to br_multicast_rcv,
    + * which would in turn call br_multicast_add_group, which would
    + * attempt to acquire multicast_lock. This function should be
    + * called after the lock has been released to avoid deadlocks on
    + * multicast_lock.
    + *
    + * br_multicast_leave_snoopers does not have the problem since
    + * br_multicast_rcv first checks BROPT_MULTICAST_ENABLED, and
    + * returns without calling br_multicast_ipv4/6_rcv if it's not
    + * enabled. Moved both functions out just for symmetry.
    + */
    + if (change_snoopers) {
    + if (br_opt_get(br, BROPT_MULTICAST_ENABLED))
    + br_multicast_join_snoopers(br);
    + else
    + br_multicast_leave_snoopers(br);
    + }
    +
    return 0;
    }

    --- a/net/bridge/br_private.h
    +++ b/net/bridge/br_private.h
    @@ -665,6 +665,8 @@ void br_multicast_del_port(struct net_br
    void br_multicast_enable_port(struct net_bridge_port *port);
    void br_multicast_disable_port(struct net_bridge_port *port);
    void br_multicast_init(struct net_bridge *br);
    +void br_multicast_join_snoopers(struct net_bridge *br);
    +void br_multicast_leave_snoopers(struct net_bridge *br);
    void br_multicast_open(struct net_bridge *br);
    void br_multicast_stop(struct net_bridge *br);
    void br_multicast_dev_del(struct net_bridge *br);
    @@ -792,6 +794,14 @@ static inline void br_multicast_init(str
    {
    }

    +static inline void br_multicast_join_snoopers(struct net_bridge *br)
    +{
    +}
    +
    +static inline void br_multicast_leave_snoopers(struct net_bridge *br)
    +{
    +}
    +
    static inline void br_multicast_open(struct net_bridge *br)
    {
    }

    \
     
     \ /
      Last update: 2020-12-19 14:05    [W:4.032 / U:0.084 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site