From e049f28883126c689cf95859480d9ee4ab23b7fa Mon Sep 17 00:00:00 2001 From: "roy.qing.li@gmail.com" Date: Mon, 17 Oct 2011 22:32:42 +0000 Subject: neigh: fix rcu splat in neigh_update() when use dst_get_neighbour to get neighbour, we need rcu_read_lock to protect, since dst_get_neighbour uses rcu_dereference. The bug was reported by Ari Savolainen [ 105.612095] [ 105.612096] =================================================== [ 105.612100] [ INFO: suspicious rcu_dereference_check() usage. ] [ 105.612101] --------------------------------------------------- [ 105.612103] include/net/dst.h:91 invoked rcu_dereference_check() without protection! [ 105.612105] [ 105.612106] other info that might help us debug this: [ 105.612106] [ 105.612108] [ 105.612108] rcu_scheduler_active = 1, debug_locks = 0 [ 105.612110] 1 lock held by dnsmasq/2618: [ 105.612111] #0: (rtnl_mutex){+.+.+.}, at: [] rtnl_lock+0x17/0x20 [ 105.612120] [ 105.612121] stack backtrace: [ 105.612123] Pid: 2618, comm: dnsmasq Not tainted 3.1.0-rc1 #41 [ 105.612125] Call Trace: [ 105.612129] [] lockdep_rcu_dereference+0xbb/0xc0 [ 105.612132] [] neigh_update+0x4f9/0x5f0 [ 105.612135] [] ? neigh_lookup+0xe1/0x220 [ 105.612139] [] arp_req_set+0xb8/0x230 [ 105.612142] [] arp_ioctl+0x1bf/0x310 [ 105.612146] [] ? lock_hrtimer_base.isra.26+0x30/0x60 [ 105.612150] [] inet_ioctl+0x85/0x90 [ 105.612154] [] sock_do_ioctl+0x30/0x70 [ 105.612157] [] sock_ioctl+0x73/0x280 [ 105.612162] [] do_vfs_ioctl+0x98/0x570 [ 105.612165] [] ? fget_light+0x340/0x3a0 [ 105.612168] [] sys_ioctl+0x4f/0x80 [ 105.612172] [] system_call_fastpath+0x16/0x1b Reported-by: Ari Savolainen Signed-off-by: RongQing Acked-by: Eric Dumazet Signed-off-by: David S. Miller --- net/core/neighbour.c | 4 ++++ 1 file changed, 4 insertions(+) (limited to 'net/core') diff --git a/net/core/neighbour.c b/net/core/neighbour.c index 43449649cf7..909ecb3c2a3 100644 --- a/net/core/neighbour.c +++ b/net/core/neighbour.c @@ -1168,10 +1168,14 @@ int neigh_update(struct neighbour *neigh, const u8 *lladdr, u8 new, struct dst_entry *dst = skb_dst(skb); struct neighbour *n2, *n1 = neigh; write_unlock_bh(&neigh->lock); + + rcu_read_lock(); /* On shaper/eql skb->dst->neighbour != neigh :( */ if (dst && (n2 = dst_get_neighbour(dst)) != NULL) n1 = n2; n1->output(n1, skb); + rcu_read_unlock(); + write_lock_bh(&neigh->lock); } skb_queue_purge(&neigh->arp_queue); -- cgit v1.2.3