[PATCH 3.4 001/146] ipv6: add check for blackhole or prohibited entry in rt6_redire

lizf
2015-09-15T10:00:39Z

From: Weilong Chen <chenweilong@huawei.com>

3.4.109-rc1 review patch. If anyone has any objections, please let me know.

------------------

There's a check for ip6_null_entry, but it's not enough if the config
CONFIG_IPV6_MULTIPLE_TABLES is selected. Blackhole or prohibited entries
should also be ignored.

This path is for kernel before v3.6, as there's a commit b94f1c0
use icmpv6_notify() instead of rt6_redirect() and rt6_redirect has
been deleted.

The oops as follow:
[exception RIP: do_raw_write_lock+12]
RIP: ffffffff8122c42c RSP: ffff880666e45820 RFLAGS: 00010282
RAX: ffff8801207bffd8 RBX: 0000000000000018 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffff880666e45898 RDI: 0000000000000018
RBP: ffff880666e45830 R8: 000000000000001e R9: 0000000006000000
R10: ffff88011796b8a0 R11: 0000000000000004 R12: ffff88010391ed00
R13: 0000000000000000 R14: ffff880666e45898 R15: ffff88011796b890
ORIG_RAX: ffffffffffffffff CS: 0010 SS: 0018
[ffff880666e45838] _raw_write_lock_bh at ffffffff81450b39
[ffff880666e45858] __ip6_ins_rt at ffffffff813ed8c1
[ffff880666e45888] ip6_ins_rt at ffffffff813eef58
[ffff880666e458b8] rt6_redirect at ffffffff813f0b84
[ffff880666e45958] ndisc_rcv at ffffffff813f95d8
[ffff880666e45a08] icmpv6_rcv at ffffffff814000e8
[ffff880666e45ae8] ip6_input_finish at ffffffff813e43bb
[ffff880666e45b38] ip6_input at ffffffff813e4b08
[ffff880666e45b68] ipv6_rcv at ffffffff813e4969
[ffff880666e45bc8] __netif_receive_skb at ffffffff8135158a
[ffff880666e45c38] dev_gro_receive at ffffffff81351cb0
[ffff880666e45c78] napi_gro_receive at ffffffff81351fc5
[ffff880666e45cb8] tg3_rx at ffffffffa0bfb354 [tg]
[ffff880666e45d88] tg3_poll_work at ffffffffa0c07857 [tg]
[ffff880666e45e18] tg3_poll_msix at ffffffffa0c07d1b [tg]
[ffff880666e45e68] net_rx_action at ffffffff81352219
[ffff880666e45ec8] __do_softirq at ffffffff8103e5a1
[ffff880666e45f38] call_softirq at ffffffff81459c4c
[ffff880666e45f50] do_softirq at ffffffff8100413d
[ffff880666e45f80] do_IRQ at ffffffff81003cce
This happened when ip6_route_redirect found a rt which was set
blackhole, the rt had a NULL rt6i_table argument which is accessed by
__ip6_ins_rt() when trying to lock rt6i_table->tb6_lock caused a BUG:
"BUG: unable to handle kernel NULL pointer"

Signed-off-by: Weilong Chen <chenweilong@huawei.com>
---
net/ipv6/route.c | 11 +++++++++++
1 file changed, 11 insertions(+)

diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index 4cfba3d..23b3304 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -1661,6 +1661,17 @@ void rt6_redirect(const struct in6_addr *dest, const struct in6_addr *src,
goto out;
}

+#ifdef CONFIG_IPV6_MULTIPLE_TABLES
+ if (rt == net->ipv6.ip6_blk_hole_entry ||
+ rt == net->ipv6.ip6_prohibit_entry) {
+ if (net_ratelimit())
+ printk(KERN_DEBUG "rt6_redirect: source isn't a valid" \
+ " nexthop for redirect target " \
+ "(blackhole or prohibited)\n");
+ goto out;
+ }
+#endif
+
/*
* We have finally decided to accept it.
*/
--
1.9.1