From 49b8e74438062aba379ce5d3f91b9e6e2e9c6745 Mon Sep 17 00:00:00 2001 From: Jim Foraker Date: Thu, 8 Aug 2013 17:44:22 -0700 Subject: [PATCH] IPoIB: Fix race in deleting ipoib_neigh entries In several places, this snippet is used when removing neigh entries: list_del(&neigh->list); ipoib_neigh_free(neigh); The list_del() removes neigh from the associated struct ipoib_path, while ipoib_neigh_free() removes neigh from the device's neigh entry lookup table. Both of these operations are protected by the priv->lock spinlock. The table however is also protected via RCU, and so naturally the lock is not held when doing reads. This leads to a race condition, in which a thread may successfully look up a neigh entry that has already been deleted from neigh->list. Since the previous deletion will have marked the entry with poison, a second list_del() on the object will cause a panic: #5 [ffff8802338c3c70] general_protection at ffffffff815108c5 [exception RIP: list_del+16] RIP: ffffffff81289020 RSP: ffff8802338c3d20 RFLAGS: 00010082 RAX: dead000000200200 RBX: ffff880433e60c88 RCX: 0000000000009e6c RDX: 0000000000000246 RSI: ffff8806012ca298 RDI: ffff880433e60c88 RBP: ffff8802338c3d30 R8: ffff8806012ca2e8 R9: 00000000ffffffff R10: 0000000000000001 R11: 0000000000000000 R12: ffff8804346b2020 R13: ffff88032a3e7540 R14: ffff8804346b26e0 R15: 0000000000000246 ORIG_RAX: ffffffffffffffff CS: 0010 SS: 0000 #6 [ffff8802338c3d38] ipoib_cm_tx_handler at ffffffffa066fe0a [ib_ipoib] #7 [ffff8802338c3d98] cm_process_work at ffffffffa05149a7 [ib_cm] #8 [ffff8802338c3de8] cm_work_handler at ffffffffa05161aa [ib_cm] #9 [ffff8802338c3e38] worker_thread at ffffffff81090e10 #10 [ffff8802338c3ee8] kthread at ffffffff81096c66 #11 [ffff8802338c3f48] kernel_thread at ffffffff8100c0ca We move the list_del() into ipoib_neigh_free(), so that deletion happens only once, after the entry has been successfully removed from the lookup table. This same behavior is already used in ipoib_del_neighs_by_gid() and __ipoib_reap_neigh(). Signed-off-by: Jim Foraker Reviewed-by: Or Gerlitz Reviewed-by: Jack Wang Reviewed-by: Shlomo Pongratz Signed-off-by: Roland Dreier --- drivers/infiniband/ulp/ipoib/ipoib_cm.c | 3 --- drivers/infiniband/ulp/ipoib/ipoib_main.c | 9 +++------ 2 files changed, 3 insertions(+), 9 deletions(-) diff --git a/drivers/infiniband/ulp/ipoib/ipoib_cm.c b/drivers/infiniband/ulp/ipoib/ipoib_cm.c index 3eceb61e3532..7a3175400b2a 100644 --- a/drivers/infiniband/ulp/ipoib/ipoib_cm.c +++ b/drivers/infiniband/ulp/ipoib/ipoib_cm.c @@ -817,7 +817,6 @@ void ipoib_cm_handle_tx_wc(struct net_device *dev, struct ib_wc *wc) if (neigh) { neigh->cm = NULL; - list_del(&neigh->list); ipoib_neigh_free(neigh); tx->neigh = NULL; @@ -1234,7 +1233,6 @@ static int ipoib_cm_tx_handler(struct ib_cm_id *cm_id, if (neigh) { neigh->cm = NULL; - list_del(&neigh->list); ipoib_neigh_free(neigh); tx->neigh = NULL; @@ -1325,7 +1323,6 @@ static void ipoib_cm_tx_start(struct work_struct *work) neigh = p->neigh; if (neigh) { neigh->cm = NULL; - list_del(&neigh->list); ipoib_neigh_free(neigh); } list_del(&p->list); diff --git a/drivers/infiniband/ulp/ipoib/ipoib_main.c b/drivers/infiniband/ulp/ipoib/ipoib_main.c index c6f71a88c55c..82cec1af902c 100644 --- a/drivers/infiniband/ulp/ipoib/ipoib_main.c +++ b/drivers/infiniband/ulp/ipoib/ipoib_main.c @@ -493,7 +493,6 @@ static void path_rec_completion(int status, path, neigh)); if (!ipoib_cm_get(neigh)) { - list_del(&neigh->list); ipoib_neigh_free(neigh); continue; } @@ -618,7 +617,6 @@ static void neigh_add_path(struct sk_buff *skb, u8 *daddr, if (!ipoib_cm_get(neigh)) ipoib_cm_set(neigh, ipoib_cm_create_tx(dev, path, neigh)); if (!ipoib_cm_get(neigh)) { - list_del(&neigh->list); ipoib_neigh_free(neigh); goto err_drop; } @@ -639,7 +637,7 @@ static void neigh_add_path(struct sk_buff *skb, u8 *daddr, neigh->ah = NULL; if (!path->query && path_rec_start(dev, path)) - goto err_list; + goto err_path; __skb_queue_tail(&neigh->queue, skb); } @@ -648,9 +646,6 @@ static void neigh_add_path(struct sk_buff *skb, u8 *daddr, ipoib_neigh_put(neigh); return; -err_list: - list_del(&neigh->list); - err_path: ipoib_neigh_free(neigh); err_drop: @@ -1098,6 +1093,8 @@ void ipoib_neigh_free(struct ipoib_neigh *neigh) rcu_assign_pointer(*np, rcu_dereference_protected(neigh->hnext, lockdep_is_held(&priv->lock))); + /* remove from parent list */ + list_del(&neigh->list); call_rcu(&neigh->rcu, ipoib_neigh_reclaim); return; } else {