[PATCH] ipvs: Fix use-after-free in ip_vs_in

[YueHaibing]

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.part.29+0xe8/0xd20 [ip_vs]
 ? tcp_in_window+0xfe0/0xfe0 [nf_conntrack]
 ? ip_vs_in_icmp+0xcc0/0xcc0 [ip_vs]
 ? ipt_do_table+0x4f1/0xad0 [ip_tables]
 ? ip_vs_out+0x126/0x8f0 [ip_vs]
 ? common_interrupt+0xa/0xf
 ip_vs_in+0xd8/0x170 [ip_vs]
 ? ip_vs_in.part.29+0xd20/0xd20 [ip_vs]
 ? nf_nat_ipv4_fn+0x21/0xc0 [nf_nat_ipv4]
 ? nf_nat_packet+0x4b/0x90 [nf_nat]
 ? nf_nat_ipv4_local_fn+0xf9/0x160 [nf_nat_ipv4]
 ? ip_vs_remote_request4+0x50/0x50 [ip_vs]
 nf_hook_slow+0x5f/0xe0
 ? sock_write_iter+0x121/0x1c0
 __ip_local_out+0x1d5/0x250
 ? ip_finish_output+0x430/0x430
 ? ip_forward_options+0x2d0/0x2d0
 ? ip_copy_addrs+0x2d/0x40
 ? __ip_queue_xmit+0x2ca/0x730
 ip_local_out+0x19/0x60
 __tcp_transmit_skb+0xba1/0x14f0
 ? __tcp_select_window+0x330/0x330
 ? pvclock_clocksource_read+0xd1/0x180
 ? kvm_sched_clock_read+0xd/0x20
 ? sched_clock+0x5/0x10
 ? sched_clock_cpu+0x18/0x100
 tcp_write_xmit+0x41f/0x1ed0
 ? _copy_from_iter_full+0xca/0x340
 __tcp_push_pending_frames+0x52/0x140
 tcp_sendmsg_locked+0x787/0x1600
 ? __wake_up_common_lock+0x80/0x130
 ? tcp_sendpage+0x60/0x60
 ? remove_wait_queue+0x84/0xb0
 ? mutex_unlock+0x1d/0x40
 ? n_tty_read+0x4f7/0xd20
 ? check_stack_object+0x21/0x60
 ? inet_sk_set_state+0xb0/0xb0
 tcp_sendmsg+0x27/0x40
 sock_sendmsg+0x6d/0x80
 sock_write_iter+0x121/0x1c0
 ? sock_sendmsg+0x80/0x80
 ? ldsem_up_read+0x13/0x40
 ? iov_iter_init+0x77/0xb0
 __vfs_write+0x23e/0x370
 ? kernel_read+0xa0/0xa0
 ? do_vfs_ioctl+0x134/0x900
 ? __set_current_blocked+0x7e/0x90
 ? __audit_syscall_entry+0x18e/0x1f0
 ? ktime_get_coarse_real_ts64+0x51/0x70
 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

Memory state around the buggy address:
 ffff8881e9b26d00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8881e9b26d80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff8881e9b26e00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                  ^
 ffff8881e9b26e80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8881e9b26f00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb

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.

Reported-by: Hulk Robot <hulkci@xxxxxxxxxx>
Fixes: efe41606184e ("ipvs: convert to use pernet nf_hook api")
Signed-off-by: YueHaibing <yuehaibing@xxxxxxxxxx>
---
 net/netfilter/ipvs/ip_vs_core.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/net/netfilter/ipvs/ip_vs_core.c b/net/netfilter/ipvs/ip_vs_core.c
index 1445755..33205db 100644
--- a/net/netfilter/ipvs/ip_vs_core.c
+++ b/net/netfilter/ipvs/ip_vs_core.c
@@ -2320,6 +2320,7 @@ static void __net_exit __ip_vs_cleanup(struct net *net)
 	ip_vs_control_net_cleanup(ipvs);
 	ip_vs_estimator_net_cleanup(ipvs);
 	IP_VS_DBG(2, "ipvs netns %d released\n", ipvs->gen);
+	synchronize_net();
 	net->ipvs = NULL;
 }
 
-- 
2.7.4