diff options
| author | Florian Westphal <fw@strlen.de> | 2019-11-15 12:39:23 +0100 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2020-01-12 11:22:47 +0100 |
| commit | 290d4aad426066d895436e062dd8ddf375257150 (patch) | |
| tree | 54cc835ae17b2dd9797b6601aa5c2b795e15136a | |
| parent | 3106fb78d3579c8e9c9b3040f7f7841981919624 (diff) | |
netfilter: ctnetlink: netns exit must wait for callbacks
[ Upstream commit 18a110b022a5c02e7dc9f6109d0bd93e58ac6ebb ]
Curtis Taylor and Jon Maxwell reported and debugged a crash on 3.10
based kernel.
Crash occurs in ctnetlink_conntrack_events because net->nfnl socket is
NULL. The nfnl socket was set to NULL by netns destruction running on
another cpu.
The exiting network namespace calls the relevant destructors in the
following order:
1. ctnetlink_net_exit_batch
This nulls out the event callback pointer in struct netns.
2. nfnetlink_net_exit_batch
This nulls net->nfnl socket and frees it.
3. nf_conntrack_cleanup_net_list
This removes all remaining conntrack entries.
This is order is correct. The only explanation for the crash so ar is:
cpu1: conntrack is dying, eviction occurs:
-> nf_ct_delete()
-> nf_conntrack_event_report \
-> nf_conntrack_eventmask_report
-> notify->fcn() (== ctnetlink_conntrack_events).
cpu1: a. fetches rcu protected pointer to obtain ctnetlink event callback.
b. gets interrupted.
cpu2: runs netns exit handlers:
a runs ctnetlink destructor, event cb pointer set to NULL.
b runs nfnetlink destructor, nfnl socket is closed and set to NULL.
cpu1: c. resumes and trips over NULL net->nfnl.
Problem appears to be that ctnetlink_net_exit_batch only prevents future
callers of nf_conntrack_eventmask_report() from obtaining the callback.
It doesn't wait of other cpus that might have already obtained the
callbacks address.
I don't see anything in upstream kernels that would prevent similar
crash: We need to wait for all cpus to have exited the event callback.
Fixes: 9592a5c01e79dbc59eb56fa ("netfilter: ctnetlink: netns support")
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
| -rw-r--r-- | net/netfilter/nf_conntrack_netlink.c | 3 |
1 files changed, 3 insertions, 0 deletions
diff --git a/net/netfilter/nf_conntrack_netlink.c b/net/netfilter/nf_conntrack_netlink.c index 3a24c01cb909..f324a1124418 100644 --- a/net/netfilter/nf_conntrack_netlink.c +++ b/net/netfilter/nf_conntrack_netlink.c @@ -3390,6 +3390,9 @@ static void __net_exit ctnetlink_net_exit_batch(struct list_head *net_exit_list) list_for_each_entry(net, net_exit_list, exit_list) ctnetlink_net_exit(net); + + /* wait for other cpus until they are done with ctnl_notifiers */ + synchronize_rcu(); } static struct pernet_operations ctnetlink_net_ops = { |