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Message-Id: <20241016030909.64932-1-clementwei90@163.com>
Date: Wed, 16 Oct 2024 11:09:09 +0800
From: Rongguang Wei <clementwei90@....com>
To: netfilter-devel@...r.kernel.org,
pablo@...filter.org,
kadlec@...filter.org
Cc: coreteam@...filter.org,
linux-kernel@...r.kernel.org,
Rongguang Wei <weirongguang@...inos.cn>
Subject: [PATCH v1] netfilter: x_tables: fix ordering of get and update table private
From: Rongguang Wei <weirongguang@...inos.cn>
Meet a kernel panic in ipt_do_table:
PANIC: "Unable to handle kernel paging request at virtual address 00706f746b736564"
and the stack is:
PC: ffff5e1dbecf0750 [ipt_do_table+1432]
LR: ffff5e1dbecf04e4 [ipt_do_table+812]
SP: ffff8021f7643370 PSTATE: 20400009
X29: ffff8021f7643390 X28: ffff802900c3990c X27: ffffa0405245a000
X26: ffff80400ad645a8 X25: ffffa0201c4d8000 X24: ffff5e1dbed00228
X23: ffff80400ad64738 X22: 0000000000000000 X21: ffff80400ad64000
X20: ffff802114980ae8 X19: ffff8021f7643570 X18: 00000007ea9ec175
X17: 0000fffde7b52460 X16: ffff5e1e181e8f20 X15: 0000fffd9a0ae078
X14: 610d273b56961dbc X13: 0a08010100007ecb X12: f5011880fd874f59
X11: ffff5e1dbed10600 X10: ffffa0405245a000 X9: 569b063f004015d5
X8: ffff80400ad64738 X7: 0000000000010002 X6: 0000000000000000
X5: 0000000000000000 X4: 0000000000000000 X3: 0000000000000000
X2: 0000000000000000 X1: 2e706f746b736564 X0: ffff80400ad65850
[ffff8021f7643390] ipt_do_table at ffff5e1dbecf074c [ip_tables]
[ffff8021f76434d0] iptable_filter_hook at ffff5e1dbfe700a4 [iptable_filter]
[ffff8021f76434f0] nf_hook_slow at ffff5e1e18c31c2c
[ffff8021f7643530] ip_forward at ffff5e1e18c41924
[ffff8021f76435a0] ip_rcv_finish at ffff5e1e18c3fddc
[ffff8021f76435d0] ip_rcv at ffff5e1e18c40214
[ffff8021f7643630] __netif_receive_skb_one_core at ffff5e1e18bbbed4
[ffff8021f7643670] __netif_receive_skb at ffff5e1e18bbbf3c
[ffff8021f7643690] process_backlog at ffff5e1e18bbd52c
[ffff8021f76436f0] __napi_poll at ffff5e1e18bbc464
[ffff8021f7643730] net_rx_action at ffff5e1e18bbc9a8
The panic happend in ipt_do_table function:
private = READ_ONCE(table->private);
jumpstack = (struct ipt_entry **)private->jumpstack[cpu];
[...]
jumpstack[stackid++] = e; // panic here
In vmcore, the cpu is 4, I read the private->jumpstack[cpu] is 007365325f6b6365,
this address between user and kernel address ranges which caused kernel panic.
Also the kmem shows that the private->jumpstack address is free.
It looks like we get a UAF address here.
But in xt_replace_table function:
private = table->private;
[...]
smp_wmb();
table->private = newtable_info;
smp_mb();
It seems no chance to get a free private member in ipt_do_table.
May have a ordering error which looks impossible:
smp_wmb();
table->private = newtable_info;
private = table->private;
smp_mb();
we get table->private after we set new table->private. After that, the
private was free in xt_free_table_info and also used in ipt_do_table.
Here use READ_ONCE to ensure we get private before we set the new one.
Signed-off-by: Rongguang Wei <weirongguang@...inos.cn>
---
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..1ce7a4f268d6 100644
--- a/net/netfilter/x_tables.c
+++ b/net/netfilter/x_tables.c
@@ -1399,7 +1399,7 @@ xt_replace_table(struct xt_table *table,
/* Do the substitution. */
local_bh_disable();
- private = table->private;
+ private = READ_ONCE(table->private);
/* Check inside lock: is the old number correct? */
if (num_counters != private->number) {
--
2.25.1
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