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SubjectRe: [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@huawei.com>
> > Fixes: efe41606184e ("ipvs: convert to use pernet nf_hook api")
> > Suggested-by: Julian Anastasov <ja@ssi.bg>
> > Signed-off-by: YueHaibing <yuehaibing@huawei.com>
>
> Looks good to me, thanks!
>
> Acked-by: Julian Anastasov <ja@ssi.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@verge.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@ssi.bg>
>

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