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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Hans Verkuil <hverkuil-cisco@xs4all.nl>,
        syzbot+ccf0a61ed12f2a7313ee@syzkaller.appspotmail.com,
        Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Subject: [PATCH 4.14 088/101] media: v4l2-tpg: array index could become negative
Date:   Mon,  7 Jan 2019 13:33:16 +0100
Message-Id: <20190107105337.702427111@linuxfoundation.org>
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References: <20190107105330.372621917@linuxfoundation.org>
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4.14-stable review patch.  If anyone has any objections, please let me know.

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

From: Hans Verkuil <hverkuil-cisco@xs4all.nl>

commit e5f71a27fa12c1a1b02ad478a568e76260f1815e upstream.

text[s] is a signed char, so using that as index into the font8x16 array
can result in negative indices. Cast it to u8 to be safe.

Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Reported-by: syzbot+ccf0a61ed12f2a7313ee@syzkaller.appspotmail.com
Cc: <stable@vger.kernel.org>      # for v4.7 and up
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/media/common/v4l2-tpg/v4l2-tpg-core.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/media/common/v4l2-tpg/v4l2-tpg-core.c
+++ b/drivers/media/common/v4l2-tpg/v4l2-tpg-core.c
@@ -1733,7 +1733,7 @@ typedef struct { u16 __; u8 _; } __packe
 		unsigned s;	\
 	\
 		for (s = 0; s < len; s++) {	\
-			u8 chr = font8x16[text[s] * 16 + line];	\
+			u8 chr = font8x16[(u8)text[s] * 16 + line];	\
 	\
 			if (hdiv == 2 && tpg->hflip) { \
 				pos[3] = (chr & (0x01 << 6) ? fg : bg);	\