From de916736aaaadddbd6061472969f667b14204aa9 Mon Sep 17 00:00:00 2001
From: "Gustavo A. R. Silva" <gustavo@embeddedor.com>
Date: Wed, 15 Aug 2018 10:50:41 -0500
Subject: [PATCH] misc: hmc6352: fix potential Spectre v1
Git-commit: de916736aaaadddbd6061472969f667b14204aa9
Patch-mainline: v4.19-rc4
References: bsc#1051510

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

This issue was detected with the help of Smatch:

drivers/misc/hmc6352.c:54 compass_store() warn: potential spectre issue
'map' [r]

Fix this by sanitizing val before using it to index map

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://marc.info/?l=linux-kernel&m=152449131114778&w=2

Cc: stable@vger.kernel.org
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 drivers/misc/hmc6352.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/misc/hmc6352.c b/drivers/misc/hmc6352.c
index eeb7eef62174..38f90e179927 100644
--- a/drivers/misc/hmc6352.c
+++ b/drivers/misc/hmc6352.c
@@ -27,6 +27,7 @@
 #include <linux/err.h>
 #include <linux/delay.h>
 #include <linux/sysfs.h>
+#include <linux/nospec.h>
 
 static DEFINE_MUTEX(compass_mutex);
 
@@ -50,6 +51,7 @@ static int compass_store(struct device *dev, const char *buf, size_t count,
 		return ret;
 	if (val >= strlen(map))
 		return -EINVAL;
+	val = array_index_nospec(val, strlen(map));
 	mutex_lock(&compass_mutex);
 	ret = compass_command(c, map[val]);
 	mutex_unlock(&compass_mutex);
-- 
2.16.4