From 1f17e2f2c8a8be3430813119fa7b633398f6185b Mon Sep 17 00:00:00 2001 From: David Ahern Date: Thu, 26 Jan 2017 13:54:08 -0800 Subject: [PATCH] net: ipv6: ignore null_entry on route dumps lkp-robot reported a BUG: [ 10.151226] BUG: unable to handle kernel NULL pointer dereference at 00000198 [ 10.152525] IP: rt6_fill_node+0x164/0x4b8 [ 10.153307] *pdpt = 0000000012ee5001 *pde = 0000000000000000 [ 10.153309] [ 10.154492] Oops: 0000 [#1] [ 10.154987] CPU: 0 PID: 909 Comm: netifd Not tainted 4.10.0-rc4-00722-g41e8c70ee162-dirty #10 [ 10.156482] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.7.5-20140531_083030-gandalf 04/01/2014 [ 10.158254] task: d0deb000 task.stack: d0e0c000 [ 10.159059] EIP: rt6_fill_node+0x164/0x4b8 [ 10.159780] EFLAGS: 00010296 CPU: 0 [ 10.160404] EAX: 00000000 EBX: d10c2358 ECX: c1f7c6cc EDX: c1f6ff44 [ 10.161469] ESI: 00000000 EDI: c2059900 EBP: d0e0dc4c ESP: d0e0dbe4 [ 10.162534] DS: 007b ES: 007b FS: 0000 GS: 0033 SS: 0068 [ 10.163482] CR0: 80050033 CR2: 00000198 CR3: 10d94660 CR4: 000006b0 [ 10.164535] Call Trace: [ 10.164993] ? paravirt_sched_clock+0x9/0xd [ 10.165727] ? sched_clock+0x9/0xc [ 10.166329] ? sched_clock_cpu+0x19/0xe9 [ 10.166991] ? lock_release+0x13e/0x36c [ 10.167652] rt6_dump_route+0x4c/0x56 [ 10.168276] fib6_dump_node+0x1d/0x3d [ 10.168913] fib6_walk_continue+0xab/0x167 [ 10.169611] fib6_walk+0x2a/0x40 [ 10.170182] inet6_dump_fib+0xfb/0x1e0 [ 10.170855] netlink_dump+0xcd/0x21f This happens when the loopback device is set down and a ipv6 fib route dump is requested. ip6_null_entry is the root of all ipv6 fib tables making it integrated into the table and hence passed to the ipv6 route dump code. The null_entry route uses the loopback device for dst.dev but may not have rt6i_idev set because of the order in which initializations are done -- ip6_route_net_init is run before addrconf_init has initialized the loopback device. Fixing the initialization order is a much bigger problem with no obvious solution thus far. The BUG is triggered when the loopback is set down and the netif_running check added by a1a22c1206 fails. The fill_node descends to checking rt->rt6i_idev for ignore_routes_with_linkdown and since rt6i_idev is NULL it faults. The null_entry route should not be processed in a dump request. Catch and ignore. This check is done in rt6_dump_route as it is the highest place in the callchain with knowledge of both the route and the network namespace. Fixes: a1a22c1206("net: ipv6: Keep nexthop of multipath route on admin down") Signed-off-by: David Ahern Signed-off-by: David S. Miller --- net/ipv6/route.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/net/ipv6/route.c b/net/ipv6/route.c index 74bb1190800e..5046d2b24004 100644 --- a/net/ipv6/route.c +++ b/net/ipv6/route.c @@ -3320,6 +3320,10 @@ nla_put_failure: int rt6_dump_route(struct rt6_info *rt, void *p_arg) { struct rt6_rtnl_dump_arg *arg = (struct rt6_rtnl_dump_arg *) p_arg; + struct net *net = arg->net; + + if (rt == net->ipv6.ip6_null_entry) + return 0; if (nlmsg_len(arg->cb->nlh) >= sizeof(struct rtmsg)) { struct rtmsg *rtm = nlmsg_data(arg->cb->nlh); @@ -3332,7 +3336,7 @@ int rt6_dump_route(struct rt6_info *rt, void *p_arg) } } - return rt6_fill_node(arg->net, + return rt6_fill_node(net, arg->skb, rt, NULL, NULL, 0, RTM_NEWROUTE, NETLINK_CB(arg->cb->skb).portid, arg->cb->nlh->nlmsg_seq, NLM_F_MULTI); -- 2.20.1