netdev - Re: [PATCH net 2/2] selftests: forwarding: bridge: add a state bypass with disabled VLAN filtering test

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Message-ID: <2252e81c-fe49-40aa-944e-4c94d5de563d@blackwall.org>
Date: Tue, 4 Nov 2025 21:10:09 +0200
From: Nikolay Aleksandrov <razor@...ckwall.org>
To: Petr Machata <petrm@...dia.com>
Cc: netdev@...r.kernel.org, tobias@...dekranz.com, idosch@...dia.com,
 kuba@...nel.org, davem@...emloft.net, bridge@...ts.linux.dev,
 pabeni@...hat.com, edumazet@...gle.com, horms@...nel.org
Subject: Re: [PATCH net 2/2] selftests: forwarding: bridge: add a state bypass
 with disabled VLAN filtering test

On 11/4/25 19:15, Petr Machata wrote:
> 
> Nikolay Aleksandrov <razor@...ckwall.org> writes:
> 
>> Add a test which checks that port state bypass cannot happen if we have
>> VLAN filtering disabled and MST enabled. Such bypass could lead to race
>> condition when deleting a port because learning may happen after its
>> state has been toggled to disabled while it's being deleted, leading to
>> a use after free.
>>
>> Signed-off-by: Nikolay Aleksandrov <razor@...ckwall.org>
>> ---
>>  .../net/forwarding/bridge_vlan_unaware.sh     | 35 ++++++++++++++++++-
>>  1 file changed, 34 insertions(+), 1 deletion(-)
>>
>> diff --git a/tools/testing/selftests/net/forwarding/bridge_vlan_unaware.sh b/tools/testing/selftests/net/forwarding/bridge_vlan_unaware.sh
>> index 2b5700b61ffa..20769793310e 100755
>> --- a/tools/testing/selftests/net/forwarding/bridge_vlan_unaware.sh
>> +++ b/tools/testing/selftests/net/forwarding/bridge_vlan_unaware.sh
>> @@ -1,7 +1,7 @@
>>  #!/bin/bash
>>  # SPDX-License-Identifier: GPL-2.0
>>  
>> -ALL_TESTS="ping_ipv4 ping_ipv6 learning flooding pvid_change"
>> +ALL_TESTS="ping_ipv4 ping_ipv6 learning flooding pvid_change mst_state_no_bypass"
> 
> I think you'll need to adjust this test for v2, can you please change
> the above line to the following while at it?
> 

ack

> ALL_TESTS="
> 	ping_ipv4
> 	ping_ipv6
> 	learning
> 	flooding
> 	pvid_change
> 	mst_state_no_bypass
> "
> 
>>  NUM_NETIFS=4
>>  source lib.sh
>>  
>> @@ -114,6 +114,39 @@ pvid_change()
>>  	ping_ipv6 " with bridge port $swp1 PVID deleted"
>>  }
>>  
>> +mst_state_no_bypass()
>> +{
>> +	local mac=de:ad:be:ef:13:37
>> +
>> +	# Test that port state isn't bypassed when MST is enabled and VLAN
>> +	# filtering is disabled
>> +	RET=0
>> +
>> +	# MST can be enabled only when there are no VLANs
>> +	bridge vlan del vid 1 dev $swp1
>> +	bridge vlan del vid 1 dev $swp2
> 
> Pretty sure these naked references will explode in the CI's shellcheck.
> I expect they'll have to be quoted as "$swp1".
> 

Oh haven't written selftests in awhile, I've missed the shellcheck stuff. :)

>> +	bridge vlan del vid 1 dev br0 self
>> +
>> +	ip link set br0 type bridge mst_enabled 1
>> +	check_err $? "Could not enable MST"
>> +
>> +	bridge link set dev $swp1 state disabled
> 
> Here as well. And more cases are below.
> 
> I've got this in my bash history. Might come in handy.
> 
>     cat files | while read file; do git show net-next/main:$file > file; shellcheck file > sc-old; git show HEAD:$file > file; shellcheck file > sc-new; echo $file; diff -u sc-old sc-new; done | less
>
 
Thanks for the hint. I'll add this to my patch review process as well.

Cheers,
 Nik

>> +	check_err $? "Could not set port state"
>> +
>> +	$MZ $h1 -c 1 -p 64 -a $mac -t ip -q
>> +
>> +	bridge fdb show brport $swp1 | grep -q de:ad:be:ef:13:37
>> +	check_fail $? "FDB entry found when it shouldn't be"
>> +
>> +	log_test "VLAN filtering disabled and MST enabled port state no bypass"
>> +
>> +	ip link set br0 type bridge mst_enabled 0
>> +	bridge link set dev $swp1 state forwarding
>> +	bridge vlan add vid 1 dev $swp1 pvid untagged
>> +	bridge vlan add vid 1 dev $swp2 pvid untagged
>> +	bridge vlan add vid 1 dev br0 self
>> +}
>> +
>>  trap cleanup EXIT
>>  
>>  setup_prepare
>