netdev - Re: NULL pointer dereference in rt6_get

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Message-ID: <20151014231705.GA79022@kafai-mba.local>
Date:	Wed, 14 Oct 2015 16:17:05 -0700
From:	Martin KaFai Lau <kafai@...com>
To:	Phil Sutter <phil@....cc>
CC:	<netdev@...r.kernel.org>,
	Hannes Frederic Sowa <hannes@...essinduktion.org>,
	Steffen Klassert <steffen.klassert@...unet.com>,
	Julian Anastasov <ja@....bg>
Subject: Re: NULL pointer dereference in rt6_get_cookie()

On Thu, Oct 15, 2015 at 12:34:13AM +0200, Phil Sutter wrote:
> Hi Martin,
>
> On Tue, Oct 13, 2015 at 11:14:21PM -0700, Martin KaFai Lau wrote:
> > On Tue, Oct 13, 2015 at 09:26:41PM +0200, Phil Sutter wrote:
> > > I have backed up the rt pointer at top of the function and restored it
> > > before pr_err, this is the output:
> > >
> > > | rt6i_dst:2001:4dd0:ff3b:13::/64 rt6i_gateway::: rt6i_flags:40000001 dst.flags:00000000
> > Hi Phil, Can you try the following patch and report the pr_err?
>
> Probably needless to say, but with your patch applied the Oops does not
> occur anymore. This is the log output:
Thanks for testing it.  The patch may need a bit refactoring work and
I will post it soon.

>
> | [   46.518869] IPv6: ort:ffff8800cbb5b800 rt6i_dst:[2001:4dd0:ff3b:13::]/64 rt6i_gateway:[::] rt6i_flags:40000001 dst.flags:00000020
> | [   46.518874] IPv6:  rt:ffff8800cb07a000 rt6i_dst:[2001:4dd0:ff3b:13::]/64 rt6i_gateway:[::] rt6i_flags:00000001 dst.flags:00000000
> | [   46.529171] IPv6: ort:ffff8800cbb5b800 rt6i_dst:[2001:4dd0:ff3b:13::]/64 rt6i_gateway:[::] rt6i_flags:40000001 dst.flags:00000020
> | [   46.529174] IPv6:  rt:ffff8800cb07b500 rt6i_dst:[2001:4dd0:ff3b:13::]/64 rt6i_gateway:[::] rt6i_flags:00000001 dst.flags:00000000
> | [   46.529187] IPv6: ort:ffff8800cbb5b800 rt6i_dst:[2001:4dd0:ff3b:13::]/64 rt6i_gateway:[::] rt6i_flags:40000001 dst.flags:00000020
> | [   46.529189] IPv6:  rt:ffff8800cb07ad80 rt6i_dst:[2001:4dd0:ff3b:13::]/64 rt6i_gateway:[::] rt6i_flags:00000001 dst.flags:00000000
> | [   47.532014] IPv6: ort:ffff8800cbb5b800 rt6i_dst:[2001:4dd0:ff3b:13::]/64 rt6i_gateway:[::] rt6i_flags:40000001 dst.flags:00000020
> | [   47.532021] IPv6:  rt:ffff8800cb07a000 rt6i_dst:[2001:4dd0:ff3b:13::]/64 rt6i_gateway:[::] rt6i_flags:00000001 dst.flags:00000000
> | [   47.532028] IPv6: ort:ffff8800cbb5b800 rt6i_dst:[2001:4dd0:ff3b:13::]/64 rt6i_gateway:[::] rt6i_flags:40000001 dst.flags:00000020
> | [   47.532031] IPv6:  rt:ffff8800cb07b500 rt6i_dst:[2001:4dd0:ff3b:13::]/64 rt6i_gateway:[::] rt6i_flags:00000001 dst.flags:00000000
> | [   49.536010] IPv6: ort:ffff8800cbb5b800 rt6i_dst:[2001:4dd0:ff3b:13::]/64 rt6i_gateway:[::] rt6i_flags:40000001 dst.flags:00000020
> | [   49.536014] IPv6:  rt:ffff8800cb07ad80 rt6i_dst:[2001:4dd0:ff3b:13::]/64 rt6i_gateway:[::] rt6i_flags:00000001 dst.flags:00000000
> | [   49.536021] IPv6: ort:ffff8800cbb5b800 rt6i_dst:[2001:4dd0:ff3b:13::]/64 rt6i_gateway:[::] rt6i_flags:40000001 dst.flags:00000020
> | [   49.536024] IPv6:  rt:ffff8800cb07a180 rt6i_dst:[2001:4dd0:ff3b:13::]/64 rt6i_gateway:[::] rt6i_flags:00000001 dst.flags:00000000
> | [   53.544013] IPv6: ort:ffff8800cbb5b800 rt6i_dst:[2001:4dd0:ff3b:13::]/64 rt6i_gateway:[::] rt6i_flags:40000001 dst.flags:00000020
> | [   53.544020] IPv6:  rt:ffff8800cb07a300 rt6i_dst:[2001:4dd0:ff3b:13::]/64 rt6i_gateway:[::] rt6i_flags:00000001 dst.flags:00000000
> | [   53.544028] IPv6: ort:ffff8800cbb5b800 rt6i_dst:[2001:4dd0:ff3b:13::]/64 rt6i_gateway:[::] rt6i_flags:40000001 dst.flags:00000020
> | [   53.544031] IPv6:  rt:ffff8800cb07b980 rt6i_dst:[2001:4dd0:ff3b:13::]/64 rt6i_gateway:[::] rt6i_flags:00000001 dst.flags:00000000
>
> In case the amount of log entries is surprising: my test-case is
> mounting two NFS shares over IPsec. No idea if that's relevant or not.
I also don't know why xfrm_lookup() errors out and then triggers
make_blackhole() but I believe it should not affect the fix here.

Thanks,
Martin
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