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 <d...@cumulusnetworks.com>
---
v2
- updated commit message; no code change
Dave: per last email you suggested putting this in fib6_dump_node, but
fib6_dump_node does not have knowledge of the network namespace
because of the way the fib_walker works. I could put
struct rt6_rtnl_dump_arg *arg = (struct rt6_rtnl_dump_arg *) w->args;
into fib6_dump_node to get the net pointer from it but did not
want to duplicate the typecast.
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 4b1f0f98a0e9..47499ed429da 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -3320,6 +3320,10 @@ static int rt6_fill_node(struct net *net,
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);
--
2.1.4
