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 <dsa@cumulusnetworks.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
1f17e2f2c8