nf_log_unregister() runs after the per-net teardown so its final RCU
grace period also drains readers that obtained the logger from a per-net
binding. However, ebt_nflog passes an explicit ULOG log type to
nf_log_packet() without holding a reference on the selected logger module,
unlike the xt_NFLOG and nft_log frontends.
An ebtables nflog rule can therefore remain callable while nfnetlink_log
is unloaded. The resulting interleaving is:
CPU 0 CPU 1
nfnetlink_log_fini()
unregister_pernet_subsys()
kfree(nfnl_log_pernet(net))
ebt_nflog_tg()
nf_log_packet()
nfulnl_log_packet()
instance_lookup_get_rcu()
The global ULOG logger is still registered at this point, so CPU 1
dereferences the per-net state after CPU 0 has freed it. KASAN reported:
BUG: KASAN: slab-use-after-free in instance_lookup_get_rcu
Read of size 8 at addr ff110001052e6210 by task poc/92
Call Trace:
instance_lookup_get_rcu+0x1ce/0x1f0 [nfnetlink_log]
nfulnl_log_packet+0x248/0x2fb0 [nfnetlink_log]
nf_log_packet+0x204/0x300
ebt_nflog_tg+0x351/0x550
ebt_do_table+0xedf/0x22b0
Allocated by task 90:
__kmalloc_noprof+0x186/0x470
ops_init+0x6d/0x420
register_pernet_operations+0x2f6/0x670
register_pernet_subsys+0x23/0x40
Freed by task 93:
kfree+0x131/0x3c0
ops_undo_list+0x3e3/0x700
unregister_pernet_operations+0x232/0x490
unregister_pernet_subsys+0x1c/0x30
nfnetlink_log_fini+0x34/0x450 [nfnetlink_log]
Acquire the ULOG logger module reference when an ebt_nflog rule is
validated and release it when the rule is destroyed. Request the NFLOG
backend for legacy callers when needed, matching xt_NFLOG. This prevents
module teardown until all ebt_nflog rules have stopped using the logger.
Fixes: c83fa19603bd ("netfilter: nf_log: don't call synchronize_rcu in
nf_log_unset")
Cc: [email protected]
Signed-off-by: Chengfeng Ye <[email protected]>
---
net/bridge/netfilter/ebt_nflog.c | 17 ++++++++++++++++-
1 file changed, 16 insertions(+), 1 deletion(-)
diff --git a/net/bridge/netfilter/ebt_nflog.c b/net/bridge/netfilter/ebt_nflog.c
index 61bf8f4465ab..426f8adc912c 100644
--- a/net/bridge/netfilter/ebt_nflog.c
+++ b/net/bridge/netfilter/ebt_nflog.c
@@ -41,11 +41,25 @@ ebt_nflog_tg(struct sk_buff *skb, const struct
xt_action_param *par)
static int ebt_nflog_tg_check(const struct xt_tgchk_param *par)
{
struct ebt_nflog_info *info = par->targinfo;
+ int ret;
if (info->flags & ~EBT_NFLOG_MASK)
return -EINVAL;
info->prefix[EBT_NFLOG_PREFIX_SIZE - 1] = '\0';
- return 0;
+
+ ret = nf_logger_find_get(par->family, NF_LOG_TYPE_ULOG);
+ if (ret != 0 && !par->nft_compat) {
+ request_module("%s", "nfnetlink_log");
+
+ ret = nf_logger_find_get(par->family, NF_LOG_TYPE_ULOG);
+ }
+
+ return ret;
+}
+
+static void ebt_nflog_tg_destroy(const struct xt_tgdtor_param *par)
+{
+ nf_logger_put(par->family, NF_LOG_TYPE_ULOG);
}
static struct xt_target ebt_nflog_tg_reg __read_mostly = {
@@ -54,6 +68,7 @@ static struct xt_target ebt_nflog_tg_reg __read_mostly = {
.family = NFPROTO_BRIDGE,
.target = ebt_nflog_tg,
.checkentry = ebt_nflog_tg_check,
+ .destroy = ebt_nflog_tg_destroy,
.targetsize = sizeof(struct ebt_nflog_info),
.me = THIS_MODULE,
};
--
2.43.0
