This is a note to let you know that I've just added the patch titled RDMA/cm: Fix ordering of xa_alloc_cyclic() in ib_create_cm_id() to the 5.6-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: rdma-cm-fix-ordering-of-xa_alloc_cyclic-in-ib_create_cm_id.patch and it can be found in the queue-5.6 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From e8dc4e885c459343970b25acd9320fe9ee5492e7 Mon Sep 17 00:00:00 2001 From: Jason Gunthorpe <jgg@xxxxxxxx> Date: Tue, 10 Mar 2020 11:25:31 +0200 Subject: RDMA/cm: Fix ordering of xa_alloc_cyclic() in ib_create_cm_id() From: Jason Gunthorpe <jgg@xxxxxxxxxxxx> commit e8dc4e885c459343970b25acd9320fe9ee5492e7 upstream. xa_alloc_cyclic() is a SMP release to be paired with some later acquire during xa_load() as part of cm_acquire_id(). As such, xa_alloc_cyclic() must be done after the cm_id is fully initialized, in particular, it absolutely must be after the refcount_set(), otherwise the refcount_inc() in cm_acquire_id() may not see the set. As there are several cases where a reader will be able to use the id.local_id after cm_acquire_id in the IB_CM_IDLE state there needs to be an unfortunate split into a NULL allocate and a finalizing xa_store. Fixes: a977049dacde ("[PATCH] IB: Add the kernel CM implementation") Link: https://lore.kernel.org/r/20200310092545.251365-2-leon@xxxxxxxxxx Signed-off-by: Leon Romanovsky <leonro@xxxxxxxxxxxx> Signed-off-by: Jason Gunthorpe <jgg@xxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- drivers/infiniband/core/cm.c | 27 +++++++++++---------------- 1 file changed, 11 insertions(+), 16 deletions(-) --- a/drivers/infiniband/core/cm.c +++ b/drivers/infiniband/core/cm.c @@ -572,18 +572,6 @@ static int cm_init_av_by_path(struct sa_ return 0; } -static int cm_alloc_id(struct cm_id_private *cm_id_priv) -{ - int err; - u32 id; - - err = xa_alloc_cyclic_irq(&cm.local_id_table, &id, cm_id_priv, - xa_limit_32b, &cm.local_id_next, GFP_KERNEL); - - cm_id_priv->id.local_id = (__force __be32)id ^ cm.random_id_operand; - return err; -} - static u32 cm_local_id(__be32 local_id) { return (__force u32) (local_id ^ cm.random_id_operand); @@ -825,6 +813,7 @@ struct ib_cm_id *ib_create_cm_id(struct void *context) { struct cm_id_private *cm_id_priv; + u32 id; int ret; cm_id_priv = kzalloc(sizeof *cm_id_priv, GFP_KERNEL); @@ -836,9 +825,6 @@ struct ib_cm_id *ib_create_cm_id(struct cm_id_priv->id.cm_handler = cm_handler; cm_id_priv->id.context = context; cm_id_priv->id.remote_cm_qpn = 1; - ret = cm_alloc_id(cm_id_priv); - if (ret) - goto error; spin_lock_init(&cm_id_priv->lock); init_completion(&cm_id_priv->comp); @@ -847,11 +833,20 @@ struct ib_cm_id *ib_create_cm_id(struct INIT_LIST_HEAD(&cm_id_priv->altr_list); atomic_set(&cm_id_priv->work_count, -1); refcount_set(&cm_id_priv->refcount, 1); + + ret = xa_alloc_cyclic_irq(&cm.local_id_table, &id, NULL, xa_limit_32b, + &cm.local_id_next, GFP_KERNEL); + if (ret) + goto error; + cm_id_priv->id.local_id = (__force __be32)id ^ cm.random_id_operand; + xa_store_irq(&cm.local_id_table, cm_local_id(cm_id_priv->id.local_id), + cm_id_priv, GFP_KERNEL); + return &cm_id_priv->id; error: kfree(cm_id_priv); - return ERR_PTR(-ENOMEM); + return ERR_PTR(ret); } EXPORT_SYMBOL(ib_create_cm_id); Patches currently in stable-queue which might be from jgg@xxxxxxxx are queue-5.6/rdma-cm-fix-ordering-of-xa_alloc_cyclic-in-ib_create_cm_id.patch queue-5.6/rdma-siw-fix-potential-siw_mem-refcnt-leak-in-siw_fastreg_mr.patch queue-5.6/rdma-uverbs-fix-a-race-with-disassociate-and-exit_mmap.patch