[PATCH AUTOSEL 5.5 016/121] RDMA/cm: Fix ordering of xa_alloc_cyclic() in ib_create_cm_id()

Sasha Levin
2020-04-11T23:40:23Z

From: Jason Gunthorpe <jgg@mellanox.com>

[ Upstream commit e8dc4e885c459343970b25acd9320fe9ee5492e7 ]

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@kernel.org
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/infiniband/core/cm.c | 27 +++++++++++----------------
1 file changed, 11 insertions(+), 16 deletions(-)

diff --git a/drivers/infiniband/core/cm.c b/drivers/infiniband/core/cm.c
index 4decc1d4cc997..1c7984bae7ab2 100644
--- a/drivers/infiniband/core/cm.c
+++ b/drivers/infiniband/core/cm.c
@@ -571,18 +571,6 @@ static int cm_init_av_by_path(struct sa_path_rec *path,
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);
@@ -836,6 +824,7 @@ struct ib_cm_id *ib_create_cm_id(struct ib_device *device,
void *context)
{
struct cm_id_private *cm_id_priv;
+ u32 id;
int ret;

cm_id_priv = kzalloc(sizeof *cm_id_priv, GFP_KERNEL);
@@ -847,9 +836,6 @@ struct ib_cm_id *ib_create_cm_id(struct ib_device *device,
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);
@@ -858,11 +844,20 @@ struct ib_cm_id *ib_create_cm_id(struct ib_device *device,
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);

--
2.20.1