ip6table_nat module unload has refcnt warning for UAF. call trace is:
WARNING: CPU: 1 PID: 379 at kernel/module/main.c:853 module_put+0x6f/0x80
Modules linked in: ip6table_nat(-)
CPU: 1 UID: 0 PID: 379 Comm: ip6tables Not tainted 6.12.0-rc4-00047-gc2ee9f594da8-dirty #205
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996),
BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014
RIP: 0010:module_put+0x6f/0x80
Call Trace:
<TASK>
get_info+0x128/0x180
do_ip6t_get_ctl+0x6a/0x430
nf_getsockopt+0x46/0x80
ipv6_getsockopt+0xb9/0x100
rawv6_getsockopt+0x42/0x190
do_sock_getsockopt+0xaa/0x180
__sys_getsockopt+0x70/0xc0
__x64_sys_getsockopt+0x20/0x30
do_syscall_64+0xa2/0x1a0
entry_SYSCALL_64_after_hwframe+0x77/0x7f
Concurrent execution of module unload and get_info() trigered the warning.
The root cause is as follows:
cpu0 cpu1
module_exit
//mod->state = MODULE_STATE_GOING
ip6table_nat_exit
xt_unregister_template
kfree(t)
//removed from templ_list
getinfo()
t = xt_find_table_lock
list_for_each_entry(tmpl, &xt_templates[af]...)
if (strcmp(tmpl->name, name))
continue; //table not found
try_module_get
list_for_each_entry(t, &xt_net->tables[af]...)
return t; //not get refcnt
module_put(t->me) //uaf
unregister_pernet_subsys
//remove table from xt_net list
While xt_table module was going away and has been removed from
xt_templates list, we couldnt get refcnt of xt_table->me. Check
module in xt_net->tables list re-traversal to fix it.
Fixes: fdacd57c79b7 ("netfilter: x_tables: never register tables by default")
Signed-off-by: Dong Chenchen <dongchenchen2@xxxxxxxxxx>
---
net/netfilter/x_tables.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/net/netfilter/x_tables.c b/net/netfilter/x_tables.c
index da5d929c7c85..709840612f0d 100644
--- a/net/netfilter/x_tables.c
+++ b/net/netfilter/x_tables.c
@@ -1269,7 +1269,7 @@ struct xt_table *xt_find_table_lock(struct net *net, u_int8_t af,
/* and once again: */
list_for_each_entry(t, &xt_net->tables[af], list)
- if (strcmp(t->name, name) == 0)
+ if (strcmp(t->name, name) == 0 && owner == t->me)
return t;
module_put(owner);
--
2.25.1
