Messages in this thread | | | Date | Mon, 26 Apr 2021 12:08:22 -0700 (PDT) | Subject | Re: [PATCH] bonding: 3ad: Fix the conflict between bond_update_slave_arr and the state machine | From | David Miller <> |
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From: Jay Vosburgh <jay.vosburgh@canonical.com> Date: Mon, 26 Apr 2021 08:22:37 -0700
> David Miller <davem@davemloft.net> wrote: > >>From: jinyiting <jinyiting@huawei.com> >>Date: Wed, 21 Apr 2021 16:38:21 +0800 >> >>> The bond works in mode 4, and performs down/up operations on the bond >>> that is normally negotiated. The probability of bond-> slave_arr is NULL >>> >>> Test commands: >>> ifconfig bond1 down >>> ifconfig bond1 up >>> >>> The conflict occurs in the following process: >>> >>> __dev_open (CPU A) >>> --bond_open >>> --queue_delayed_work(bond->wq,&bond->ad_work,0); >>> --bond_update_slave_arr >>> --bond_3ad_get_active_agg_info >>> >>> ad_work(CPU B) >>> --bond_3ad_state_machine_handler >>> --ad_agg_selection_logic >>> >>> ad_work runs on cpu B. In the function ad_agg_selection_logic, all >>> agg->is_active will be cleared. Before the new active aggregator is >>> selected on CPU B, bond_3ad_get_active_agg_info failed on CPU A, >>> bond->slave_arr will be set to NULL. The best aggregator in >>> ad_agg_selection_logic has not changed, no need to update slave arr. >>> >>> The conflict occurred in that ad_agg_selection_logic clears >>> agg->is_active under mode_lock, but bond_open -> bond_update_slave_arr >>> is inspecting agg->is_active outside the lock. >>> >>> Also, bond_update_slave_arr is normal for potential sleep when >>> allocating memory, so replace the WARN_ON with a call to might_sleep. >>> >>> Signed-off-by: jinyiting <jinyiting@huawei.com> >>> --- >>> >>> Previous versions: >>> * https://lore.kernel.org/netdev/612b5e32-ea11-428e-0c17-e2977185f045@huawei.com/ >>> >>> drivers/net/bonding/bond_main.c | 7 ++++--- >>> 1 file changed, 4 insertions(+), 3 deletions(-) >>> >>> diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c >>> index 74cbbb2..83ef62d 100644 >>> --- a/drivers/net/bonding/bond_main.c >>> +++ b/drivers/net/bonding/bond_main.c >>> @@ -4406,7 +4404,9 @@ int bond_update_slave_arr(struct bonding *bond, struct slave *skipslave) >>> if (BOND_MODE(bond) == BOND_MODE_8023AD) { >>> struct ad_info ad_info; >>> >>> + spin_lock_bh(&bond->mode_lock); >> >>The code paths that call this function with mode_lock held will now deadlock. > > No path should be calling bond_update_slave_arr with mode_lock > already held (it expects RTNL only); did you find one? > > My concern is that there's something else that does the opposite > order, i.e., mode_lock first, then RTNL, but I haven't found an example. >
This patch is removing a lockdep assertion masking sure that mode_lock was held when this function was called. That should have been triggering all the time, right?
Thanks.
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