linux-kernel - [PATCH] IB/hfi1: Fix Spectre v1 vulnerability

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Date:   Wed, 31 Jul 2019 12:54:28 -0500
From:   "Gustavo A. R. Silva" <gustavo@...eddedor.com>
To:     Mike Marciniszyn <mike.marciniszyn@...el.com>,
        Dennis Dalessandro <dennis.dalessandro@...el.com>,
        Doug Ledford <dledford@...hat.com>,
        Jason Gunthorpe <jgg@...pe.ca>, Ira Weiny <ira.weiny@...el.com>
Cc:     linux-rdma@...r.kernel.org, linux-kernel@...r.kernel.org,
        "Gustavo A. R. Silva" <gustavo@...eddedor.com>
Subject: [PATCH] IB/hfi1: Fix Spectre v1 vulnerability

sl is controlled by user-space, hence leading to a potential
exploitation of the Spectre variant 1 vulnerability.

Fix this by sanitizing sl before using it to index ibp->sl_to_sc.

Notice that given that speculation windows are large, the policy is
to kill the speculation on the first load and not worry if it can be
completed with a dependent load/store [1].

[1] https://lore.kernel.org/lkml/20180423164740.GY17484@dhcp22.suse.cz/

Cc: stable@...r.kernel.org
Signed-off-by: Gustavo A. R. Silva <gustavo@...eddedor.com>
---
 drivers/infiniband/hw/hfi1/verbs.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/infiniband/hw/hfi1/verbs.c b/drivers/infiniband/hw/hfi1/verbs.c
index f4ca436118ab..9f53f63b1453 100644
--- a/drivers/infiniband/hw/hfi1/verbs.c
+++ b/drivers/infiniband/hw/hfi1/verbs.c
@@ -54,6 +54,7 @@
 #include <linux/mm.h>
 #include <linux/vmalloc.h>
 #include <rdma/opa_addr.h>
+#include <linux/nospec.h>
 
 #include "hfi.h"
 #include "common.h"
@@ -1537,6 +1538,7 @@ static int hfi1_check_ah(struct ib_device *ibdev, struct rdma_ah_attr *ah_attr)
 	sl = rdma_ah_get_sl(ah_attr);
 	if (sl >= ARRAY_SIZE(ibp->sl_to_sc))
 		return -EINVAL;
+	sl = array_index_nospec(sl, ARRAY_SIZE(ibp->sl_to_sc));
 
 	sc5 = ibp->sl_to_sc[sl];
 	if (sc_to_vlt(dd, sc5) > num_vls && sc_to_vlt(dd, sc5) != 0xf)
-- 
2.22.0