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Date: Tue, 20 Apr 2021 11:22:41 +0800 From: jin yiting <jinyiting@...wei.com> To: Jay Vosburgh <jay.vosburgh@...onical.com> CC: <vfalico@...il.com>, <andy@...yhouse.net>, <davem@...emloft.net>, <kuba@...nel.org>, <netdev@...r.kernel.org>, <security@...nel.org>, <linux-kernel@...r.kernel.org>, <xuhanbing@...wei.com>, <wangxiaogang3@...wei.com> Subject: Re: [PATCH] bonding: 3ad: update slave arr after initialize 在 2021/4/16 12:28, Jay Vosburgh 写道: > jinyiting <jinyiting@...wei.com> wrote: > >> From: jin yiting <jinyiting@...wei.com> >> >> 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. >> >> Signed-off-by: jin yiting <jinyiting@...wei.com> >> --- >> drivers/net/bonding/bond_3ad.c | 6 ++++++ >> 1 file changed, 6 insertions(+) >> >> diff --git a/drivers/net/bonding/bond_3ad.c b/drivers/net/bonding/bond_3ad.c >> index 6908822..d100079 100644 >> --- a/drivers/net/bonding/bond_3ad.c >> +++ b/drivers/net/bonding/bond_3ad.c >> @@ -2327,6 +2327,12 @@ void bond_3ad_state_machine_handler(struct work_struct *work) >> >> aggregator = __get_first_agg(port); >> ad_agg_selection_logic(aggregator, &update_slave_arr); >> + if (!update_slave_arr) { >> + struct aggregator *active = __get_active_agg(aggregator); >> + >> + if (active && active->is_active) >> + update_slave_arr = true; >> + } >> } >> bond_3ad_set_carrier(bond); >> } > > The described issue is a race condition (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). I don't see how the above change will reliably manage this; > the real issue looks to be that bond_update_slave_arr is committing > changes to the array (via bond_reset_slave_arr) based on a racy > inspection of the active aggregator state while it is in flux. > > Also, the description of the issue says "The best aggregator in > ad_agg_selection_logic has not changed, no need to update slave arr," > but the change above does the opposite, and will set update_slave_arr > when the aggregator has not changed (update_slave_arr remains false at > return of ad_agg_selection_logic). > > I believe I understand the described problem, but I don't see > how the patch fixes it. I suspect (but haven't tested) that the proper > fix is to acquire mode_lock in bond_update_slave_arr while calling > bond_3ad_get_active_agg_info to avoid conflict with the state machine. > > -J > > --- > -Jay Vosburgh, jay.vosburgh@...onical.com > . > Thank you for your reply. The last patch does have redundant update slave arr.Thank you for your correction. As you said, holding mode_lock in bond_update_slave_arr while calling bond_3ad_get_active_agg_info can avoid conflictwith the state machine. I have tested this patch, with ifdown/ifup operations for bond or slaves. But bond_update_slave_arr is expected to hold RTNL only and NO other lock. And it have WARN_ON(lockdep_is_held(&bond->mode_lock)); in bond_update_slave_arr. I'm not sure that holding mode_lock in bond_update_slave_arr while calling bond_3ad_get_active_agg_info is a correct action. diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c index 74cbbb2..db988e5 100644 --- a/drivers/net/bonding/bond_main.c +++ b/drivers/net/bonding/bond_main.c @@ -4406,7 +4406,9 @@ 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); if (bond_3ad_get_active_agg_info(bond, &ad_info)) { + spin_unlock_bh(&bond->mode_lock); pr_debug("bond_3ad_get_active_agg_info failed\n"); /* No active aggragator means it's not safe to use * the previous array. @@ -4414,6 +4416,7 @@ int bond_update_slave_arr(struct bonding *bond, struct slave *skipslave) bond_reset_slave_arr(bond); goto out; } + spin_unlock_bh(&bond->mode_lock); agg_id = ad_info.aggregator_id; } bond_for_each_slave(bond, slave, iter) {
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