From: jin yiting <[email protected]>
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 <[email protected]>
---
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);
}
--
1.7.12.4
jinyiting <[email protected]> wrote:
>From: jin yiting <[email protected]>
>
>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 <[email protected]>
>---
> 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, [email protected]
在 2021/4/16 12:28, Jay Vosburgh 写道:
> jinyiting <[email protected]> wrote:
>
>> From: jin yiting <[email protected]>
>>
>> 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 <[email protected]>
>> ---
>> 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, [email protected]
> .
>
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) {
jin yiting <[email protected]> wrote:
[...]
>> 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, [email protected]
>> .
>>
>
> 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.
That WARN_ON came up in discussion recently, and my opinion is
that it's incorrect, and is trying to insure bond_update_slave_arr is
safe for a potential sleep when allocating memory.
https://lore.kernel.org/netdev/[email protected]/
The original authors haven't replied, so I would suggest you
remove the WARN_ON and the surrounding CONFIG_LOCKDEP ifdefs as part of
your patch and replace it with a call to might_sleep.
The other callers of bond_3ad_get_active_agg_info are generally
obtaining the state in order to report it to user space, so I think it's
safe to leave those calls not holding the mode_lock. The race is still
there, but the data returned to user space is a snapshot and so may
reflect an incomplete state during a transition. Further, having the
inspection functions acquire the mode_lock permits user space to spam
the lock with little effort.
-J
>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) {
---
-Jay Vosburgh, [email protected]
?? 2021/4/20 13:04, Jay Vosburgh д??:
> jin yiting <[email protected]> wrote:
> [...]
>>> 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, [email protected]
>>> .
>>>
>>
>> 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.
>
> That WARN_ON came up in discussion recently, and my opinion is
> that it's incorrect, and is trying to insure bond_update_slave_arr is
> safe for a potential sleep when allocating memory.
>
> https://lore.kernel.org/netdev/[email protected]/
>
> The original authors haven't replied, so I would suggest you
> remove the WARN_ON and the surrounding CONFIG_LOCKDEP ifdefs as part of
> your patch and replace it with a call to might_sleep.
>
> The other callers of bond_3ad_get_active_agg_info are generally
> obtaining the state in order to report it to user space, so I think it's
> safe to leave those calls not holding the mode_lock. The race is still
> there, but the data returned to user space is a snapshot and so may
> reflect an incomplete state during a transition. Further, having the
> inspection functions acquire the mode_lock permits user space to spam
> the lock with little effort.
>
> -J
>
>> 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) {
>
> ---
> -Jay Vosburgh, [email protected]
> .
>
I have remove the WARN_ON and the surrounding CONFIG_LOCKDEP ifdefs in
the new patch and replace it with a call to might_sleep.
And I will send a new patch again.
Thank you for your guidance.
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
@@ -4391,9 +4391,7 @@ int bond_update_slave_arr(struct bonding *bond,
struct slave *skipslave)
int agg_id = 0;
int ret = 0;
-#ifdef CONFIG_LOCKDEP
- WARN_ON(lockdep_is_held(&bond->mode_lock));
-#endif
+ might_sleep();
usable_slaves = kzalloc(struct_size(usable_slaves, arr,
bond->slave_cnt), GFP_KERNEL);
@@ -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);
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 +4414,7 @@ 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) {
--