netfilter: nfnl_cthelper: reject del request if helper obj is in use
We can still delete the ct helper even if it is in use, this will cause
a use-after-free error. In more detail, I mean:
# nfct helper add ssdp inet udp
# iptables -t raw -A OUTPUT -p udp -j CT --helper ssdp
# nfct helper delete ssdp //--> oops, succeed!
BUG: unable to handle kernel paging request at 000026ca
IP: 0x26ca
[...]
Call Trace:
? ipv4_helper+0x62/0x80 [nf_conntrack_ipv4]
nf_hook_slow+0x21/0xb0
ip_output+0xe9/0x100
? ip_fragment.constprop.54+0xc0/0xc0
ip_local_out+0x33/0x40
ip_send_skb+0x16/0x80
udp_send_skb+0x84/0x240
udp_sendmsg+0x35d/0xa50
So add reference count to fix this issue, if ct helper is used by
others, reject the delete request.
Apply this patch:
# nfct helper delete ssdp
nfct v1.4.3: netlink error: Device or resource busy
Signed-off-by: Liping Zhang <zlpnobody@gmail.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
3 files changed