Commit de916736 authored Aug 15, 2018 by Gustavo A. R. Silva Committed by Greg Kroah-Hartman Sep 12, 2018

misc: hmc6352: fix potential Spectre v1

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>

parent 86503bd3

drivers/misc/hmc6352.c

+2 −0

Original line number	Diff line number	Diff line
		@@ -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);

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