linux-kernel - [PATCH] media: v4l2-jpeg: correct the skip count in jpeg_parse_app14

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Date:   Fri, 16 Dec 2022 16:30:33 +0800
From:   Ming Qian <ming.qian@....com>
To:     mchehab@...nel.org, mirela.rabulea@....nxp.com,
        hverkuil-cisco@...all.nl
Cc:     shawnguo@...nel.org, s.hauer@...gutronix.de, kernel@...gutronix.de,
        festevam@...il.com, xiahong.bao@....com, linux-imx@....com,
        linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
        devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: [PATCH] media: v4l2-jpeg: correct the skip count in jpeg_parse_app14_data

The curr pointer has advanced 14 bytes in jpeg_parse_app14_data.
1. jpeg_get_word_be(stream), it goes forward 2 bytes.
2. jpeg_skip(stream, 11), it goes forward 11 bytes.
3. jpeg_get_byte(stream), it goes forward 1 bytes.

so the remain bytes of this segment should be (lp - 2 - 11 - 1),
but not (lp - 2 - 11).

if driver skip 1 extra bytes, the following parsing may go wrong.

Fixes: b8035f7988a8 ("media: Add parsing for APP14 data segment in jpeg helpers")
Signed-off-by: Ming Qian <ming.qian@....com>
---
 drivers/media/v4l2-core/v4l2-jpeg.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/media/v4l2-core/v4l2-jpeg.c b/drivers/media/v4l2-core/v4l2-jpeg.c
index c2513b775f6a..75c2af763d55 100644
--- a/drivers/media/v4l2-core/v4l2-jpeg.c
+++ b/drivers/media/v4l2-core/v4l2-jpeg.c
@@ -474,7 +474,7 @@ static int jpeg_parse_app14_data(struct jpeg_stream *stream,
 	*tf = ret;
 
 	/* skip the rest of the segment, this ensures at least it is complete */
-	skip = lp - 2 - 11;
+	skip = lp - 2 - 11 - 1;
 	return jpeg_skip(stream, skip);
 }
 
-- 
2.38.1