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[11/11] vsp1_rwpf: fix potential Spectre variant 1

Message ID 54ddd5303a6964e1295a4f5d009e683810fc3c18.1524499368.git.gustavo@embeddedor.com (mailing list archive)
State Not Applicable
Delegated to: Geert Uytterhoeven
Headers show

Commit Message

Gustavo A. R. Silva April 23, 2018, 5:52 p.m. UTC
code->index can be controlled by user-space, hence leading to
a potential exploitation of the Spectre variant 1 vulnerability.

Smatch warning:
drivers/media/platform/vsp1/vsp1_rwpf.c:47 vsp1_rwpf_enum_mbus_code() warn: potential spectre issue 'codes'

Fix this by sanitizing code->index before using it to index
codes.

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
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
---
 drivers/media/platform/vsp1/vsp1_rwpf.c | 3 +++
 1 file changed, 3 insertions(+)
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Patch

diff --git a/drivers/media/platform/vsp1/vsp1_rwpf.c b/drivers/media/platform/vsp1/vsp1_rwpf.c
index cfd8f19..6e887be 100644
--- a/drivers/media/platform/vsp1/vsp1_rwpf.c
+++ b/drivers/media/platform/vsp1/vsp1_rwpf.c
@@ -13,6 +13,8 @@ 
 
 #include <media/v4l2-subdev.h>
 
+#include <linux/nospec.h>
+
 #include "vsp1.h"
 #include "vsp1_rwpf.h"
 #include "vsp1_video.h"
@@ -44,6 +46,7 @@  static int vsp1_rwpf_enum_mbus_code(struct v4l2_subdev *subdev,
 	if (code->index >= ARRAY_SIZE(codes))
 		return -EINVAL;
 
+	code->index = array_index_nospec(code->index, ARRAY_SIZE(codes));
 	code->code = codes[code->index];
 
 	return 0;