Re: [PATCH] nf_queue: Make the queue_handler pernet

[Pablo Neira Ayuso <pablo@netfilter.org>]

On Fri, May 13, 2016 at 09:18:52PM -0500, Eric W. Biederman wrote:
> 
> Florian Weber reported:
> > Under full load (unshare() in loop -> OOM conditions) we can
> > get kernel panic:
> >
> > BUG: unable to handle kernel NULL pointer dereference at 0000000000000008
> > IP: [<ffffffff81476c85>] nfqnl_nf_hook_drop+0x35/0x70
> > [..]
> > task: ffff88012dfa3840 ti: ffff88012dffc000 task.ti: ffff88012dffc000
> > RIP: 0010:[<ffffffff81476c85>]  [<ffffffff81476c85>] nfqnl_nf_hook_drop+0x35/0x70
> > RSP: 0000:ffff88012dfffd80  EFLAGS: 00010206
> > RAX: 0000000000000008 RBX: ffffffff81add0c0 RCX: ffff88013fd80000
> > [..]
> > Call Trace:
> >  [<ffffffff81474d98>] nf_queue_nf_hook_drop+0x18/0x20
> >  [<ffffffff814738eb>] nf_unregister_net_hook+0xdb/0x150
> >  [<ffffffff8147398f>] netfilter_net_exit+0x2f/0x60
> >  [<ffffffff8141b088>] ops_exit_list.isra.4+0x38/0x60
> >  [<ffffffff8141b652>] setup_net+0xc2/0x120
> >  [<ffffffff8141bd09>] copy_net_ns+0x79/0x120
> >  [<ffffffff8106965b>] create_new_namespaces+0x11b/0x1e0
> >  [<ffffffff810698a7>] unshare_nsproxy_namespaces+0x57/0xa0
> >  [<ffffffff8104baa2>] SyS_unshare+0x1b2/0x340
> >  [<ffffffff81608276>] entry_SYSCALL_64_fastpath+0x1e/0xa8
> > Code: 65 00 48 89 e5 41 56 41 55 41 54 53 83 e8 01 48 8b 97 70 12 00 00 48 98 49 89 f4 4c 8b 74 c2 18 4d 8d 6e 08 49 81 c6 88 00 00 00 <49> 8b 5d 00 48 85 db 74 1a 48 89 df 4c 89 e2 48 c7 c6 90 68 47
> >
> 
> The simple fix for this requires a new pernet variable for struct
> nf_queue that indicates when it is safe to use the dynamically
> allocated nf_queue state.
> 
> As we need a variable anyway make nf_register_queue_handler and
> nf_unregister_queue_handler pernet.  This allows the existing logic of
> when it is safe to use the state from the nfnetlink_queue module to be
> reused with no changes except for making it per net.
> 
> The syncrhonize_rcu from nf_unregister_queue_handler is moved to a new
> function nfnl_queue_net_exit_batch so that the worst case of having a
> syncrhonize_rcu in the pernet exit path is not experienced in batch
> mode.

Applied, thanks.