Eric W. Biederman 21b5944350 net: Fix double free and memory corruption in get_net_ns_by_id() ... (I can trivially verify that that idr_remove in cleanup_net happens after the network namespace count has dropped to zero --EWB) Function get_net_ns_by_id() does not check for net::count after it has found a peer in netns_ids idr. It may dereference a peer, after its count has already been finaly decremented. This leads to double free and memory corruption: put_net(peer) rtnl_lock() atomic_dec_and_test(&peer->count) [count=0] ... __put_net(peer) get_net_ns_by_id(net, id) spin_lock(&cleanup_list_lock) list_add(&net->cleanup_list, &cleanup_list) spin_unlock(&cleanup_list_lock) queue_work() peer = idr_find(&net->netns_ids, id) | get_net(peer) [count=1] | ... | (use after final put) v ... cleanup_net() ... spin_lock(&cleanup_list_lock) ... list_replace_init(&cleanup_list, ..) ... spin_unlock(&cleanup_list_lock) ... ... ... ... put_net(peer) ... atomic_dec_and_test(&peer->count) [count=0] ... spin_lock(&cleanup_list_lock) ... list_add(&net->cleanup_list, &cleanup_list) ... spin_unlock(&cleanup_list_lock) ... queue_work() ... rtnl_unlock() rtnl_lock() ... for_each_net(tmp) { ... id = __peernet2id(tmp, peer) ... spin_lock_irq(&tmp->nsid_lock) ... idr_remove(&tmp->netns_ids, id) ... ... ... net_drop_ns() ... net_free(peer) ... } ... | v cleanup_net() ... (Second free of peer) Also, put_net() on the right cpu may reorder with left's cpu list_replace_init(&cleanup_list, ..), and then cleanup_list will be corrupted. Since cleanup_net() is executed in worker thread, while put_net(peer) can happen everywhere, there should be enough time for concurrent get_net_ns_by_id() to pick the peer up, and the race does not seem to be unlikely. The patch fixes the problem in standard way. (Also, there is possible problem in peernet2id_alloc(), which requires check for net::count under nsid_lock and maybe_get_net(peer), but in current stable kernel it's used under rtnl_lock() and it has to be safe. Openswitch begun to use peernet2id_alloc(), and possibly it should be fixed too. While this is not in stable kernel yet, so I'll send a separate message to netdev@ later). Cc: Nicolas Dichtel <nicolas.dichtel@6wind.com> Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com> Fixes: 0c7aecd4bd "netns: add rtnl cmd to add and get peer netns ids" Reviewed-by: Andrey Ryabinin <aryabinin@virtuozzo.com> Reviewed-by: "Eric W. Biederman" <ebiederm@xmission.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com> Reviewed-by: Eric Dumazet <edumazet@google.com> Acked-by: Nicolas Dichtel <nicolas.dichtel@6wind.com> Signed-off-by: David S. Miller <davem@davemloft.net>		2017-12-20 12:42:22 -05:00
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datagram.c
dev.c
dev_addr_lists.c
dev_ioctl.c
devlink.c
drop_monitor.c
dst.c
dst_cache.c
ethtool.c
fib_notifier.c
fib_rules.c
filter.c
flow_dissector.c
gen_estimator.c
gen_stats.c
gro_cells.c
hwbm.c
link_watch.c
lwt_bpf.c
lwtunnel.c
Makefile
neighbour.c
net-procfs.c
net-sysfs.c
net-sysfs.h
net-traces.c
net_namespace.c
netclassid_cgroup.c
netevent.c
netpoll.c
netprio_cgroup.c
pktgen.c
ptp_classifier.c
request_sock.c
rtnetlink.c
scm.c
secure_seq.c
skbuff.c
sock.c
sock_diag.c
sock_reuseport.c
stream.c
sysctl_net_core.c
timestamping.c
tso.c
utils.c