Two parallel calls to batadv_neigh_node_new() might race for creating and adding the same neig_node. Fix this by including the check for any already existing, identical neigh_node within the spin-lock.

This fixes splats like the following:

[ 739.535069] ------------[ cut here ]------------ [ 739.535079] WARNING: CPU: 0 PID: 0 at /usr/src/batman-adv/git/batman-adv/net/batman-adv/bat_iv_ogm.c:1004 batadv_iv_ogm_process_per_outif+0xe3f/0xe60 [batman_adv]() [ 739.535092] too many matching neigh_nodes [ 739.535094] Modules linked in: dm_mod tun ip6table_filter ip6table_mangle ip6table_nat nf_nat_ipv6 ip6_tables xt_nat iptable_nat nf_nat_ipv4 nf_nat xt_TCPMSS xt_mark iptable_mangle xt_tcpudp xt_conntrack iptable_filter ip_tables x_tables ip_gre ip_tunnel gre bridge stp llc thermal_sys kvm_intel kvm crct10dif_pclmul crc32_pclmul sha256_ssse3 sha256_generic hmac drbg ansi_cprng aesni_intel aes_x86_64 lrw gf128mul glue_helper ablk_helper cryptd evdev pcspkr ip6_gre ip6_tunnel tunnel6 batman_adv(O) libcrc32c nf_conntrack_ipv6 nf_defrag_ipv6 nf_conntrack_ipv4 nf_defrag_ipv4 nf_conntrack autofs4 ext4 crc16 mbcache jbd2 xen_netfront xen_blkfront crc32c_intel [ 739.535177] CPU: 0 PID: 0 Comm: swapper/0 Tainted: G W O 4.2.0-0.bpo.1-amd64 #1 Debian 4.2.6-3~bpo8+2 [ 739.535186] 0000000000000000 ffffffffa013b050 ffffffff81554521 ffff88007d003c18 [ 739.535201] ffffffff8106fa01 0000000000000000 ffff8800047a087a ffff880079c3a000 [ 739.735602] ffff88007b82bf40 ffff88007bc2d1c0 ffffffff8106fa7a ffffffffa013aa8e [ 739.735624] Call Trace: [ 739.735639] <IRQ> [<ffffffff81554521>] ? dump_stack+0x40/0x50 [ 739.735677] [<ffffffff8106fa01>] ? warn_slowpath_common+0x81/0xb0 [ 739.735692] [<ffffffff8106fa7a>] ? warn_slowpath_fmt+0x4a/0x50 [ 739.735715] [<ffffffffa012448f>] ? batadv_iv_ogm_process_per_outif+0xe3f/0xe60 [batman_adv] [ 739.735740] [<ffffffffa0124813>] ? batadv_iv_ogm_receive+0x363/0x380 [batman_adv] [ 739.735762] [<ffffffffa0124813>] ? batadv_iv_ogm_receive+0x363/0x380 [batman_adv] [ 739.735783] [<ffffffff810b0841>] ? __raw_callee_save___pv_queued_spin_unlock+0x11/0x20 [ 739.735804] [<ffffffffa012cb39>] ? batadv_batman_skb_recv+0xc9/0x110 [batman_adv] [ 739.735825] [<ffffffff81464891>] ? __netif_receive_skb_core+0x841/0x9a0 [ 739.735838] [<ffffffff810b0841>] ? __raw_callee_save___pv_queued_spin_unlock+0x11/0x20 [ 739.735853] [<ffffffff81465681>] ? process_backlog+0xa1/0x140 [ 739.735864] [<ffffffff81464f1a>] ? net_rx_action+0x20a/0x320 [ 739.735878] [<ffffffff81073aa7>] ? __do_softirq+0x107/0x270 [ 739.735891] [<ffffffff81073d82>] ? irq_exit+0x92/0xa0 [ 739.735905] [<ffffffff8137e0d1>] ? xen_evtchn_do_upcall+0x31/0x40 [ 739.735924] [<ffffffff8155b8fe>] ? xen_do_hypervisor_callback+0x1e/0x40 [ 739.735939] <EOI> [<ffffffff810013aa>] ? xen_hypercall_sched_op+0xa/0x20 [ 739.735965] [<ffffffff810013aa>] ? xen_hypercall_sched_op+0xa/0x20 [ 739.735979] [<ffffffff8100a39c>] ? xen_safe_halt+0xc/0x20 [ 739.735991] [<ffffffff8101da6c>] ? default_idle+0x1c/0xa0 [ 739.736004] [<ffffffff810abf6b>] ? cpu_startup_entry+0x2eb/0x350 [ 739.736019] [<ffffffff81b2af5e>] ? start_kernel+0x480/0x48b [ 739.736032] [<ffffffff81b2d116>] ? xen_start_kernel+0x507/0x511 [ 739.736048] ---[ end trace c106bb901244bc8c ]---

Reported-by: Martin Weinelt martin@darmstadt.freifunk.net Signed-off-by: Linus Lüssing linus.luessing@c0d3.blue --- net/batman-adv/originator.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/net/batman-adv/originator.c b/net/batman-adv/originator.c index 070896f..59602be 100644 --- a/net/batman-adv/originator.c +++ b/net/batman-adv/originator.c @@ -637,6 +637,8 @@ batadv_neigh_node_new(struct batadv_orig_node *orig_node, struct batadv_neigh_node *neigh_node; struct batadv_hardif_neigh_node *hardif_neigh = NULL;

+ spin_lock_bh(&orig_node->neigh_list_lock); + neigh_node = batadv_neigh_node_get(orig_node, hard_iface, neigh_addr); if (neigh_node) goto out; @@ -668,9 +670,7 @@ batadv_neigh_node_new(struct batadv_orig_node *orig_node, kref_init(&neigh_node->refcount); kref_get(&neigh_node->refcount);

- spin_lock_bh(&orig_node->neigh_list_lock); hlist_add_head_rcu(&neigh_node->list, &orig_node->neigh_list); - spin_unlock_bh(&orig_node->neigh_list_lock);

/* increment unique neighbor refcount */ kref_get(&hardif_neigh->refcount); @@ -680,6 +680,8 @@ batadv_neigh_node_new(struct batadv_orig_node *orig_node, neigh_addr, orig_node->orig, hard_iface->net_dev->name);

out: + spin_unlock_bh(&orig_node->neigh_list_lock); + if (hardif_neigh) batadv_hardif_neigh_put(hardif_neigh); return neigh_node;