linux-kernel - [PATCH 05/11] omap_vout: fix potential Spectre variant 1

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Date:   Mon, 23 Apr 2018 12:41:59 -0500
From:   "Gustavo A. R. Silva" <gustavo@...eddedor.com>
To:     Mauro Carvalho Chehab <mchehab@...nel.org>,
        linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
        "Gustavo A. R. Silva" <gustavo@...eddedor.com>,
        Dan Carpenter <dan.carpenter@...cle.com>
Subject: [PATCH 05/11] omap_vout: fix potential Spectre variant 1

index can be controlled by user-space, hence leading to a
potential exploitation of the Spectre variant 1 vulnerability.

Smatch warning:
drivers/media/platform/omap/omap_vout.c:1062 vidioc_enum_fmt_vid_out() warn: potential spectre issue 'omap_formats'

Fix this by sanitizing index before using it to index
omap_formats.

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@...r.kernel.org
Reported-by: Dan Carpenter <dan.carpenter@...cle.com>
Signed-off-by: Gustavo A. R. Silva <gustavo@...eddedor.com>
---
 drivers/media/platform/omap/omap_vout.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/media/platform/omap/omap_vout.c b/drivers/media/platform/omap/omap_vout.c
index 5700b78..1a7ec39 100644
--- a/drivers/media/platform/omap/omap_vout.c
+++ b/drivers/media/platform/omap/omap_vout.c
@@ -51,6 +51,8 @@
 #include "omap_voutdef.h"
 #include "omap_vout_vrfb.h"
 
+#include <linux/nospec.h>
+
 MODULE_AUTHOR("Texas Instruments");
 MODULE_DESCRIPTION("OMAP Video for Linux Video out driver");
 MODULE_LICENSE("GPL");
@@ -1059,6 +1061,7 @@ static int vidioc_enum_fmt_vid_out(struct file *file, void *fh,
 	if (index >= NUM_OUTPUT_FORMATS)
 		return -EINVAL;
 
+	index = array_index_nospec(index, NUM_OUTPUT_FORMATS);
 	fmt->flags = omap_formats[index].flags;
 	strlcpy(fmt->description, omap_formats[index].description,
 			sizeof(fmt->description));
-- 
2.7.4