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Subject[PATCH v2] ipvs: Fix use-after-free in ip_vs_in
Date
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>
---
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

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