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From:   Peilin Ye <yepeilin.cs@gmail.com>
To:     Mauro Carvalho Chehab <mchehab@kernel.org>
Cc:     Peilin Ye <yepeilin.cs@gmail.com>,
        Hans Verkuil <hans.verkuil@cisco.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        linux-media@vger.kernel.org,
        linux-kernel-mentees@lists.linuxfoundation.org,
        syzkaller-bugs@googlegroups.com, linux-kernel@vger.kernel.org
Subject: [Linux-kernel-mentees] [PATCH] v4l2-tpg: Fix global-out-of-bounds read in precalculate_color()
Date:   Mon, 10 Aug 2020 01:05:32 -0400
Message-Id: <20200810050532.640075-1-yepeilin.cs@gmail.com>
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Sender: linux-kernel-owner@vger.kernel.org
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precalculate_color() is reading out of `sin` since `tpg->hue` is not being
properly checked. Fix it. `cos` is safe, as long as `tpg->hue` is higher
than or equal to -192.

Fixes: 63881df94d3e ("[media] vivid: add the Test Pattern Generator")
Reported-and-tested-by: syzbot+02d9172bf4c43104cd70@syzkaller.appspotmail.com
Link: https://syzkaller.appspot.com/bug?id=db50123c788e2cc5a9d90de569c398b66293ee48
Signed-off-by: Peilin Ye <yepeilin.cs@gmail.com>
---
 drivers/media/common/v4l2-tpg/v4l2-tpg-core.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/media/common/v4l2-tpg/v4l2-tpg-core.c b/drivers/media/common/v4l2-tpg/v4l2-tpg-core.c
index 50f1e0b28b25..52205fe096f7 100644
--- a/drivers/media/common/v4l2-tpg/v4l2-tpg-core.c
+++ b/drivers/media/common/v4l2-tpg/v4l2-tpg-core.c
@@ -930,6 +930,9 @@ static void precalculate_color(struct tpg_data *tpg, int k)
 		/* Implement these operations */
 		int tmp_cb, tmp_cr;
 
+		if (tpg->hue < -128 || tpg->hue > 128)
+			return;
+
 		/* First convert to YCbCr */
 
 		color_to_ycbcr(tpg, r, g, b, &y, &cb, &cr);
-- 
2.25.1