FAILED: patch "[PATCH] IB/hfi1, qib: Ensure RCU is locked when accessing list" failed to apply to 4.9-stable tree

FAILED: patch "[PATCH] IB/hfi1, qib: Ensure RCU is locked when accessing list" failed to apply to 4.9-stable tree

[gregkh]

The patch below does not apply to the 4.9-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 817a68a6584aa08e323c64283fec5ded7be84759 Mon Sep 17 00:00:00 2001
From: Dennis Dalessandro <dennis.dalessandro@intel.com>
Date: Tue, 25 Feb 2020 14:54:45 -0500
Subject: [PATCH] IB/hfi1, qib: Ensure RCU is locked when accessing list

The packet handling function, specifically the iteration of the qp list
for mad packet processing misses locking RCU before running through the
list. Not only is this incorrect, but the list_for_each_entry_rcu() call
can not be called with a conditional check for lock dependency. Remedy
this by invoking the rcu lock and unlock around the critical section.

This brings MAD packet processing in line with what is done for non-MAD
packets.

Fixes: 7724105686e7 ("IB/hfi1: add driver files")
Link: https://lore.kernel.org/r/20200225195445.140896.41873.stgit@awfm-01.aw.intel.com
Reviewed-by: Mike Marciniszyn <mike.marciniszyn@intel.com>
Signed-off-by: Dennis Dalessandro <dennis.dalessandro@intel.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>

diff --git a/drivers/infiniband/hw/hfi1/verbs.c b/drivers/infiniband/hw/hfi1/verbs.c
index 089e201d7550..2f6323ad9c59 100644
--- a/drivers/infiniband/hw/hfi1/verbs.c
+++ b/drivers/infiniband/hw/hfi1/verbs.c
@@ -515,10 +515,11 @@ static inline void hfi1_handle_packet(struct hfi1_packet *packet,
 				       opa_get_lid(packet->dlid, 9B));
 		if (!mcast)
 			goto drop;
+		rcu_read_lock();
 		list_for_each_entry_rcu(p, &mcast->qp_list, list) {
 			packet->qp = p->qp;
 			if (hfi1_do_pkey_check(packet))
-				goto drop;
+				goto unlock_drop;
 			spin_lock_irqsave(&packet->qp->r_lock, flags);
 			packet_handler = qp_ok(packet);
 			if (likely(packet_handler))
@@ -527,6 +528,7 @@ static inline void hfi1_handle_packet(struct hfi1_packet *packet,
 				ibp->rvp.n_pkt_drops++;
 			spin_unlock_irqrestore(&packet->qp->r_lock, flags);
 		}
+		rcu_read_unlock();
 		/*
 		 * Notify rvt_multicast_detach() if it is waiting for us
 		 * to finish.
diff --git a/drivers/infiniband/hw/qib/qib_verbs.c b/drivers/infiniband/hw/qib/qib_verbs.c
index 33778d451b82..5ef93f8f17a1 100644
--- a/drivers/infiniband/hw/qib/qib_verbs.c
+++ b/drivers/infiniband/hw/qib/qib_verbs.c
@@ -329,8 +329,10 @@ void qib_ib_rcv(struct qib_ctxtdata *rcd, void *rhdr, void *data, u32 tlen)
 		if (mcast == NULL)
 			goto drop;
 		this_cpu_inc(ibp->pmastats->n_multicast_rcv);
+		rcu_read_lock();
 		list_for_each_entry_rcu(p, &mcast->qp_list, list)
 			qib_qp_rcv(rcd, hdr, 1, data, tlen, p->qp);
+		rcu_read_unlock();
 		/*
 		 * Notify rvt_multicast_detach() if it is waiting for us
 		 * to finish.