Re: [PATCH net] net: nsid cannot be allocated for a dead netns

Andrei reports the following kmemleak error:
unreferenced object 0xffff91badb543950 (size 2096):
  comm "kworker/u4:0", pid 6, jiffies 4295152553 (age 28.418s)
  hex dump (first 32 bytes):
    00 00 00 00 00 00 00 00 00 cb 5f df ba 91 ff ff  .........._.....
    00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
  backtrace:
    [<ffffffffb1865bea>] kmemleak_alloc+0x4a/0xa0
    [<ffffffffb1243b38>] kmem_cache_alloc+0x128/0x280
    [<ffffffffb142f5ab>] idr_layer_alloc+0x2b/0x90
    [<ffffffffb142f9cd>] idr_get_empty_slot+0x34d/0x370
    [<ffffffffb142fa4e>] idr_alloc+0x5e/0x110
    [<ffffffffb170ac3d>] __peernet2id_alloc+0x6d/0x90
    [<ffffffffb170bda5>] peernet2id_alloc+0x55/0xb0
    [<ffffffffb1731216>] rtnl_fill_ifinfo+0xaa6/0x10a0
    [<ffffffffb1733073>] rtmsg_ifinfo_build_skb+0x73/0xd0
    [<ffffffffb17125d5>] rollback_registered_many+0x295/0x390
    [<ffffffffb1712765>] unregister_netdevice_many+0x25/0x80
    [<ffffffffb17138a5>] default_device_exit_batch+0x145/0x170
    [<ffffffffb170ae52>] ops_exit_list.isra.4+0x52/0x60
    [<ffffffffb170c17f>] cleanup_net+0x1bf/0x2a0
    [<ffffffffb10b616f>] process_one_work+0x1ff/0x660
    [<ffffffffb10b661e>] worker_thread+0x4e/0x480

There is no reason to try to allocate an nsid for a netns which is dying.

Reported-by: Andrei Vagin <redacted>
Signed-off-by: Nicolas Dichtel <redacted>
---

Thank you for the report. Can you test this patch?

Regards,
Nicolas

 net/core/net_namespace.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/net/core/net_namespace.c b/net/core/net_namespace.c
index f61c0e02a413..f1340ed0d8df 100644
--- a/net/core/net_namespace.c
+++ b/net/core/net_namespace.c

@@ -159,6 +159,9 @@ static int alloc_netid(struct net *net, struct net *peer, int reqid)
 		max = reqid + 1;
 	}

+	if (!atomic_read(&net->count) || !&atomic_read(peer->count))