[PATCH] RDMA/cma: prevent rdma id destroy during cma_iw_handler

[Shin'ichiro Kawasaki]

When rdma_destroy_id() and cma_iw_handler() race, struct rdma_id_private
*id_priv can be destroyed during cma_iw_handler call. This causes "BUG:
KASAN: slab-use-after-free" at mutex_lock() in cma_iw_handler().
To prevent the destroy of id_priv, keep its reference count by calling
cma_id_get() and cma_id_put() at start and end of cma_iw_handler().

Signed-off-by: Shin'ichiro Kawasaki <shinichiro.kawasaki at wdc.com>
Cc: stable at vger.kernel.org
---
The BUG KASAN was observed with blktests at test cases nvme/030 or nvme/031,
using SIW transport [1]. To reproduce it, it is required to repeat the test
cases from 30 to 50 times on my test system.

[1] https://lore.kernel.org/linux-block/rsmmxrchy6voi5qhl4irss5sprna3f5owkqtvybxglcv2pnylm@xmrnpfu3tfpe/

 drivers/infiniband/core/cma.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/infiniband/core/cma.c b/drivers/infiniband/core/cma.c
index 93a1c48d0c32..c5267d9bb184 100644
--- a/drivers/infiniband/core/cma.c
+++ b/drivers/infiniband/core/cma.c
@@ -2477,6 +2477,7 @@ static int cma_iw_handler(struct iw_cm_id *iw_id, struct iw_cm_event *iw_event)
 	struct sockaddr *laddr = (struct sockaddr *)&iw_event->local_addr;
 	struct sockaddr *raddr = (struct sockaddr *)&iw_event->remote_addr;
 
+	cma_id_get(id_priv);
 	mutex_lock(&id_priv->handler_mutex);
 	if (READ_ONCE(id_priv->state) != RDMA_CM_CONNECT)
 		goto out;
@@ -2524,12 +2525,14 @@ static int cma_iw_handler(struct iw_cm_id *iw_id, struct iw_cm_event *iw_event)
 	if (ret) {
 		/* Destroy the CM ID by returning a non-zero value. */
 		id_priv->cm_id.iw = NULL;
+		cma_id_put(id_priv);
 		destroy_id_handler_unlock(id_priv);
 		return ret;
 	}
 
 out:
 	mutex_unlock(&id_priv->handler_mutex);
+	cma_id_put(id_priv);
 	return ret;
 }
 
-- 
2.40.1