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Date:   Tue, 21 May 2019 17:18:06 +0200
From:   Simon Horman <horms@...ge.net.au>
To:     Julian Anastasov <ja@....bg>
Cc:     YueHaibing <yuehaibing@...wei.com>, davem@...emloft.net,
        wensong@...ux-vs.org, pablo@...filter.org,
        kadlec@...ckhole.kfki.hu, fw@...len.de,
        linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
        lvs-devel@...r.kernel.org, netfilter-devel@...r.kernel.org,
        coreteam@...filter.org
Subject: Re: [PATCH v2] ipvs: Fix use-after-free in ip_vs_in

On Sun, May 19, 2019 at 01:09:24PM +0300, Julian Anastasov wrote:
> 
> 	Hello,
> 
> On Fri, 17 May 2019, YueHaibing wrote:
> 
> > BUG: KASAN: use-after-free in ip_vs_in.part.29+0xe8/0xd20 [ip_vs]
> > Read of size 4 at addr ffff8881e9b26e2c by task sshd/5603
> > 
> > CPU: 0 PID: 5603 Comm: sshd Not tainted 4.19.39+ #30
> > Hardware name: Red Hat KVM, BIOS 0.5.1 01/01/2011
> > Call Trace:
> >  dump_stack+0x71/0xab
> >  print_address_description+0x6a/0x270
> >  kasan_report+0x179/0x2c0
> >  ip_vs_in.part.29+0xe8/0xd20 [ip_vs]
> >  ip_vs_in+0xd8/0x170 [ip_vs]
> >  nf_hook_slow+0x5f/0xe0
> >  __ip_local_out+0x1d5/0x250
> >  ip_local_out+0x19/0x60
> >  __tcp_transmit_skb+0xba1/0x14f0
> >  tcp_write_xmit+0x41f/0x1ed0
> >  ? _copy_from_iter_full+0xca/0x340
> >  __tcp_push_pending_frames+0x52/0x140
> >  tcp_sendmsg_locked+0x787/0x1600
> >  ? tcp_sendpage+0x60/0x60
> >  ? inet_sk_set_state+0xb0/0xb0
> >  tcp_sendmsg+0x27/0x40
> >  sock_sendmsg+0x6d/0x80
> >  sock_write_iter+0x121/0x1c0
> >  ? sock_sendmsg+0x80/0x80
> >  __vfs_write+0x23e/0x370
> >  vfs_write+0xe7/0x230
> >  ksys_write+0xa1/0x120
> >  ? __ia32_sys_read+0x50/0x50
> >  ? __audit_syscall_exit+0x3ce/0x450
> >  do_syscall_64+0x73/0x200
> >  entry_SYSCALL_64_after_hwframe+0x44/0xa9
> > RIP: 0033:0x7ff6f6147c60
> > Code: 73 01 c3 48 8b 0d 28 12 2d 00 f7 d8 64 89 01 48 83 c8 ff c3 66 0f 1f 44 00 00 83 3d 5d 73 2d 00 00 75 10 b8 01 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 31 c3 48 83
> > RSP: 002b:00007ffd772ead18 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
> > RAX: ffffffffffffffda RBX: 0000000000000034 RCX: 00007ff6f6147c60
> > RDX: 0000000000000034 RSI: 000055df30a31270 RDI: 0000000000000003
> > RBP: 000055df30a31270 R08: 0000000000000000 R09: 0000000000000000
> > R10: 00007ffd772ead70 R11: 0000000000000246 R12: 00007ffd772ead74
> > R13: 00007ffd772eae20 R14: 00007ffd772eae24 R15: 000055df2f12ddc0
> > 
> > Allocated by task 6052:
> >  kasan_kmalloc+0xa0/0xd0
> >  __kmalloc+0x10a/0x220
> >  ops_init+0x97/0x190
> >  register_pernet_operations+0x1ac/0x360
> >  register_pernet_subsys+0x24/0x40
> >  0xffffffffc0ea016d
> >  do_one_initcall+0x8b/0x253
> >  do_init_module+0xe3/0x335
> >  load_module+0x2fc0/0x3890
> >  __do_sys_finit_module+0x192/0x1c0
> >  do_syscall_64+0x73/0x200
> >  entry_SYSCALL_64_after_hwframe+0x44/0xa9
> > 
> > Freed by task 6067:
> >  __kasan_slab_free+0x130/0x180
> >  kfree+0x90/0x1a0
> >  ops_free_list.part.7+0xa6/0xc0
> >  unregister_pernet_operations+0x18b/0x1f0
> >  unregister_pernet_subsys+0x1d/0x30
> >  ip_vs_cleanup+0x1d/0xd2f [ip_vs]
> >  __x64_sys_delete_module+0x20c/0x300
> >  do_syscall_64+0x73/0x200
> >  entry_SYSCALL_64_after_hwframe+0x44/0xa9
> > 
> > The buggy address belongs to the object at ffff8881e9b26600 which belongs to the cache kmalloc-4096 of size 4096
> > The buggy address is located 2092 bytes inside of 4096-byte region [ffff8881e9b26600, ffff8881e9b27600)
> > The buggy address belongs to the page:
> > page:ffffea0007a6c800 count:1 mapcount:0 mapping:ffff888107c0e600 index:0x0 compound_mapcount: 0
> > flags: 0x17ffffc0008100(slab|head)
> > raw: 0017ffffc0008100 dead000000000100 dead000000000200 ffff888107c0e600
> > raw: 0000000000000000 0000000080070007 00000001ffffffff 0000000000000000
> > page dumped because: kasan: bad access detected
> > 
> > while unregistering ipvs module, ops_free_list calls
> > __ip_vs_cleanup, then nf_unregister_net_hooks be called to
> > do remove nf hook entries. It need a RCU period to finish,
> > however net->ipvs is set to NULL immediately, which will
> > trigger NULL pointer dereference when a packet is hooked
> > and handled by ip_vs_in where net->ipvs is dereferenced.
> > 
> > Another scene is ops_free_list call ops_free to free the
> > net_generic directly while __ip_vs_cleanup finished, then
> > calling ip_vs_in will triggers use-after-free.
> > 
> > This patch moves nf_unregister_net_hooks from __ip_vs_cleanup()
> > to __ip_vs_dev_cleanup(),  where rcu_barrier() is called by
> > unregister_pernet_device -> unregister_pernet_operations,
> > that will do the needed grace period.
> > 
> > Reported-by: Hulk Robot <hulkci@...wei.com>
> > Fixes: efe41606184e ("ipvs: convert to use pernet nf_hook api")
> > Suggested-by: Julian Anastasov <ja@....bg>
> > Signed-off-by: YueHaibing <yuehaibing@...wei.com>
> 
> 	Looks good to me, thanks!
> 
> Acked-by: Julian Anastasov <ja@....bg>
> 
> 	It should restore the order of unregistrations before
> the mentioned commit and to ensure grace period before stopping
> the traffic and unregistering ipvs_core_ops where traffic is not
> expected.

Signed-off-by: Simon Horman <horms@...ge.net.au>

Pablo, could you consider applying this to nf?

> 
> > ---
> > v2: fix by moving nf_unregister_net_hooks from __ip_vs_cleanup() to __ip_vs_dev_cleanup()
> > ---
> >  net/netfilter/ipvs/ip_vs_core.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/net/netfilter/ipvs/ip_vs_core.c b/net/netfilter/ipvs/ip_vs_core.c
> > index 14457551bcb4..8ebf21149ec3 100644
> > --- a/net/netfilter/ipvs/ip_vs_core.c
> > +++ b/net/netfilter/ipvs/ip_vs_core.c
> > @@ -2312,7 +2312,6 @@ static void __net_exit __ip_vs_cleanup(struct net *net)
> >  {
> >  	struct netns_ipvs *ipvs = net_ipvs(net);
> >  
> > -	nf_unregister_net_hooks(net, ip_vs_ops, ARRAY_SIZE(ip_vs_ops));
> >  	ip_vs_service_net_cleanup(ipvs);	/* ip_vs_flush() with locks */
> >  	ip_vs_conn_net_cleanup(ipvs);
> >  	ip_vs_app_net_cleanup(ipvs);
> > @@ -2327,6 +2326,7 @@ static void __net_exit __ip_vs_dev_cleanup(struct net *net)
> >  {
> >  	struct netns_ipvs *ipvs = net_ipvs(net);
> >  	EnterFunction(2);
> > +	nf_unregister_net_hooks(net, ip_vs_ops, ARRAY_SIZE(ip_vs_ops));
> >  	ipvs->enable = 0;	/* Disable packet reception */
> >  	smp_wmb();
> >  	ip_vs_sync_net_cleanup(ipvs);
> > -- 
> > 2.20.1
> 
> Regards
> 
> --
> Julian Anastasov <ja@....bg>
> 

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