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From:   Ben Hutchings <ben@decadent.org.uk>
To:     linux-kernel@vger.kernel.org, stable@vger.kernel.org
CC:     akpm@linux-foundation.org, "Andrzej Hajda" <a.hajda@samsung.com>,
        "Dan Carpenter" <dan.carpenter@oracle.com>,
        "Thierry Reding" <treding@nvidia.com>
Date:   Sun, 09 Dec 2018 21:50:33 +0000
Message-ID: <lsq.1544392233.428540732@decadent.org.uk>
Subject: [PATCH 3.16 035/328] drm/panel: type promotion bug in
 s6e8aa0_read_mtp_id()
In-Reply-To: <lsq.1544392232.713909046@decadent.org.uk>
Sender: linux-kernel-owner@vger.kernel.org
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3.16.62-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Dan Carpenter <dan.carpenter@oracle.com>

commit cd0e0ca69109d025b1a1b6609f70682db62138b0 upstream.

The ARRAY_SIZE() macro is type size_t.  If s6e8aa0_dcs_read() returns a
negative error code, then "ret < ARRAY_SIZE(id)" is false because the
negative error code is type promoted to a high positive value.

Fixes: 02051ca06371 ("drm/panel: add S6E8AA0 driver")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Andrzej Hajda <a.hajda@samsung.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180704093807.s3lqsb2v6dg2k43d@kili.mountain
[bwh: Backported to 3.16: adjust filename]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
 drivers/gpu/drm/panel/panel-s6e8aa0.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/gpu/drm/panel/panel-s6e8aa0.c
+++ b/drivers/gpu/drm/panel/panel-s6e8aa0.c
@@ -832,7 +832,7 @@ static void s6e8aa0_read_mtp_id(struct s
 	int ret, i;
 
 	ret = s6e8aa0_dcs_read(ctx, 0xd1, id, ARRAY_SIZE(id));
-	if (ret < ARRAY_SIZE(id) || id[0] == 0x00) {
+	if (ret < 0 || ret < ARRAY_SIZE(id) || id[0] == 0x00) {
 		dev_err(ctx->dev, "read id failed\n");
 		ctx->error = -EIO;
 		return;