linux-kernel - [PATCH AUTOSEL 4.19 24/32] IB/core: Add mitigation for Spectre V1

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Date:   Tue,  6 Aug 2019 17:35:12 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     "Luck, Tony" <tony.luck@...el.com>,
        Doug Ledford <dledford@...hat.com>,
        Sasha Levin <sashal@...nel.org>, linux-rdma@...r.kernel.org
Subject: [PATCH AUTOSEL 4.19 24/32] IB/core: Add mitigation for Spectre V1

From: "Luck, Tony" <tony.luck@...el.com>

[ Upstream commit 61f259821dd3306e49b7d42a3f90fb5a4ff3351b ]

Some processors may mispredict an array bounds check and
speculatively access memory that they should not. With
a user supplied array index we like to play things safe
by masking the value with the array size before it is
used as an index.

Signed-off-by: Tony Luck <tony.luck@...el.com>
Link: https://lore.kernel.org/r/20190731043957.GA1600@agluck-desk2.amr.corp.intel.com
Signed-off-by: Doug Ledford <dledford@...hat.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/infiniband/core/user_mad.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/infiniband/core/user_mad.c b/drivers/infiniband/core/user_mad.c
index c34a6852d691f..a18f3f8ad77fe 100644
--- a/drivers/infiniband/core/user_mad.c
+++ b/drivers/infiniband/core/user_mad.c
@@ -49,6 +49,7 @@
 #include <linux/sched.h>
 #include <linux/semaphore.h>
 #include <linux/slab.h>
+#include <linux/nospec.h>
 
 #include <linux/uaccess.h>
 
@@ -868,11 +869,14 @@ static int ib_umad_unreg_agent(struct ib_umad_file *file, u32 __user *arg)
 
 	if (get_user(id, arg))
 		return -EFAULT;
+	if (id >= IB_UMAD_MAX_AGENTS)
+		return -EINVAL;
 
 	mutex_lock(&file->port->file_mutex);
 	mutex_lock(&file->mutex);
 
-	if (id >= IB_UMAD_MAX_AGENTS || !__get_agent(file, id)) {
+	id = array_index_nospec(id, IB_UMAD_MAX_AGENTS);
+	if (!__get_agent(file, id)) {
 		ret = -EINVAL;
 		goto out;
 	}
-- 
2.20.1