linux-kernel - [PATCH] backlight: sky81452: unsure while loop does not allow negative array indexing

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Message-Id: <20200226195739.6462-1-colin.king@canonical.com>
Date:   Wed, 26 Feb 2020 19:57:39 +0000
From:   Colin King <colin.king@...onical.com>
To:     Lee Jones <lee.jones@...aro.org>,
        Daniel Thompson <daniel.thompson@...aro.org>,
        Jingoo Han <jingoohan1@...il.com>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
        Gyungoh Yoo <jack.yoo@...worksinc.com>,
        Bryan Wu <cooloney@...il.com>, dri-devel@...ts.freedesktop.org,
        linux-fbdev@...r.kernel.org
Cc:     kernel-janitors@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] backlight: sky81452: unsure while loop does not allow negative array indexing

From: Colin Ian King <colin.king@...onical.com>

In the unlikely event that num_entry is zero, the while loop
pre-decrements num_entry to cause negative array indexing into the
array sources. Fix this by iterating only if num_entry >= 0.

Addresses-Coverity: ("Out-of-bounds read")
Fixes: f705806c9f35 ("backlight: Add support Skyworks SKY81452 backlight driver")
Signed-off-by: Colin Ian King <colin.king@...onical.com>
---
 drivers/video/backlight/sky81452-backlight.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/video/backlight/sky81452-backlight.c b/drivers/video/backlight/sky81452-backlight.c
index 2355f00f5773..f456930ce78e 100644
--- a/drivers/video/backlight/sky81452-backlight.c
+++ b/drivers/video/backlight/sky81452-backlight.c
@@ -200,7 +200,7 @@ static struct sky81452_bl_platform_data *sky81452_bl_parse_dt(
 		}
 
 		pdata->enable = 0;
-		while (--num_entry)
+		while (--num_entry >= 0)
 			pdata->enable |= (1 << sources[num_entry]);
 	}
 
-- 
2.25.0