Re: [PATCH 4.9 41/51] fib_rules: return 0 directly if an exactly same rule exists when NLM_F_EXCL not supplied

[Sasha Levin <sashal@kernel.org>]

On Sun, May 19, 2019 at 08:43:48AM -0700, Nathan Chancellor wrote:
>On Wed, May 15, 2019 at 12:56:16PM +0200, Greg Kroah-Hartman wrote:
>> From: Hangbin Liu <liuhangbin@gmail.com>
>>
>> [ Upstream commit e9919a24d3022f72bcadc407e73a6ef17093a849 ]
>>
>> With commit 153380ec4b9 ("fib_rules: Added NLM_F_EXCL support to
>> fib_nl_newrule") we now able to check if a rule already exists. But this
>> only works with iproute2. For other tools like libnl, NetworkManager,
>> it still could add duplicate rules with only NLM_F_CREATE flag, like
>>
>> [localhost ~ ]# ip rule
>> 0:      from all lookup local
>> 32766:  from all lookup main
>> 32767:  from all lookup default
>> 100000: from 192.168.7.5 lookup 5
>> 100000: from 192.168.7.5 lookup 5
>>
>> As it doesn't make sense to create two duplicate rules, let's just return
>> 0 if the rule exists.
>>
>> Fixes: 153380ec4b9 ("fib_rules: Added NLM_F_EXCL support to fib_nl_newrule")
>> Reported-by: Thomas Haller <thaller@redhat.com>
>> Signed-off-by: Hangbin Liu <liuhangbin@gmail.com>
>> Signed-off-by: David S. Miller <davem@davemloft.net>
>> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
>> ---
>>  net/core/fib_rules.c |    6 +++---
>>  1 file changed, 3 insertions(+), 3 deletions(-)
>>
>> --- a/net/core/fib_rules.c
>> +++ b/net/core/fib_rules.c
>> @@ -429,9 +429,9 @@ int fib_nl_newrule(struct sk_buff *skb,
>>  	if (rule->l3mdev && rule->table)
>>  		goto errout_free;
>>
>> -	if ((nlh->nlmsg_flags & NLM_F_EXCL) &&
>> -	    rule_exists(ops, frh, tb, rule)) {
>> -		err = -EEXIST;
>> +	if (rule_exists(ops, frh, tb, rule)) {
>> +		if (nlh->nlmsg_flags & NLM_F_EXCL)
>> +			err = -EEXIST;
>>  		goto errout_free;
>>  	}
>>
>>
>>
>
>Hi all,
>
>This commit is causing issues on Android devices when Wi-Fi and mobile
>data are both enabled. The device will do a soft reboot consistently.
>So far, I've had reports on the Pixel 3 XL, OnePlus 6, Pocophone, and
>Note 9 and I can reproduce on my OnePlus 6.

Is this something that happens with Linus's tree as well? or is this a
backport issue?

>Sorry for taking so long to report this, I just figured out how to
>reproduce it today and I didn't want to report it without that.

FWIW, if you see anything suspicious with -stable patches just let us
know separately from a "better" bug report for upstream, then we can at
least temporary pull it out of the stable queue while the issue is being
addressed.

--
Thanks,
Sasha