Messages in this thread | | | Subject | Re: NULL pointer dereference in selinux_ip_postroute_compat | From | Eric Dumazet <> | Date | Wed, 08 Aug 2012 21:29:40 +0200 |
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On Wed, 2012-08-08 at 12:14 -0700, John Stultz wrote: > On 08/07/2012 03:37 PM, John Stultz wrote: > > On 08/07/2012 03:17 PM, Serge E. Hallyn wrote: > >> Quoting Paul Moore (paul@paul-moore.com): > >>> On Tue, Aug 7, 2012 at 5:58 PM, John Stultz <john.stultz@linaro.org> > >>> wrote: > >>>> On 08/07/2012 02:50 PM, Paul Moore wrote: > >>>>> On Tue, Aug 7, 2012 at 2:12 PM, John Stultz <john.stultz@linaro.org> > >>>>> wrote: > >>>>>> Hi, > >>>>>> With my kvm environment using 3.6-rc1+, I'm seeing NULL > >>>>>> pointer > >>>>>> dereferences in selinux_ip_postroute_compat(). It looks like the > >>>>>> sksec > >>>>>> value > >>>>>> is null and we die in the following line: > >>>>>> > >>>>>> if (selinux_xfrm_postroute_last(sksec->sid, skb, &ad, proto)) > >>>>>> > >>>>>> This triggers every time I shutdown the machine, but has also > >>>>>> triggered > >>>>>> randomly after a few hours. > [snip] > >> The problem seems to be that selinux_nf_ip_init() was called, which > >> registers the selinux_ipv4_ops (and ipv6). Those should not get > >> registered > >> if selinux ends up not being loaded (as in, if apparmor is loaded > >> first), > >> since as you've found here the selinux lsm hooks won't be called to set > >> call selinux_sk_alloc_security(). > > This sounds about right: > > root@testvm:~# dmesg | grep SELinux > > [ 0.004578] SELinux: Initializing. > > [ 0.005704] SELinux: Starting in permissive mode > > [ 2.235034] SELinux: Registering netfilter hooks > > > >> I assume what's happening is that > >> CONFIG_SECURITY_SELINUX_BOOTPARAM_VALUE was > >> set to 1, but selinux ended up being set to disabled after the > >> __initcall(selinux_nf_ip_init) ran? Weird. > > This looks right as well: > > > > # zcat config.gz | grep SELINUX > > CONFIG_SECURITY_SELINUX=y > > CONFIG_SECURITY_SELINUX_BOOTPARAM=y > > CONFIG_SECURITY_SELINUX_BOOTPARAM_VALUE=1 > > CONFIG_SECURITY_SELINUX_DISABLE=y > > CONFIG_SECURITY_SELINUX_DEVELOP=y > > CONFIG_SECURITY_SELINUX_AVC_STATS=y > > CONFIG_SECURITY_SELINUX_CHECKREQPROT_VALUE=1 > > # CONFIG_SECURITY_SELINUX_POLICYDB_VERSION_MAX is not set > > CONFIG_DEFAULT_SECURITY_SELINUX=y > > > > > > Since the problem isn't completely obvious, I'm starting a bisection > > to narrow this down some more. > > So I bisected this down and it seems to be the following commit: > > commit be9f4a44e7d41cee50ddb5f038fc2391cbbb4046 > Author: Eric Dumazet <edumazet@google.com> > Date: Thu Jul 19 07:34:03 2012 +0000 > > ipv4: tcp: remove per net tcp_sock > > > It doesn't revert totally cleanly, but after fixing up the rejections > and booting with this patch removed on top of Linus' head the oops on > shutdown goes away.
Thanks for doing this.
So sk_security is NULL and selinux crashes on it.
I guess I need to call security_sk_alloc().
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