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]

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@xxxxxxxxx>
> >
> > [ 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@xxxxxxxxxx>
> > Signed-off-by: Hangbin Liu <liuhangbin@xxxxxxxxx>
> > Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
> > Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
> > ---
> >  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