linux-kernel - [PATCH] agp: check for index out of range before accessing maxes

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Message-Id: <20180906111930.18743-1-colin.king@canonical.com>
Date:   Thu,  6 Sep 2018 12:19:30 +0100
From:   Colin King <colin.king@...onical.com>
To:     David Airlie <airlied@...ux.ie>, Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     kernel-janitors@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] agp: check for index out of range before accessing maxes_table[index]

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

Currently maxes_table[index] is accessed before index is checked to
be out of range.  Fix this by performing the out of range check on
index first.  Also don't check against a hard-coded maximum value
but use the array size instead.

Detected by static analysis with cppcheck:
"Array index 'index' is used before limits check"

Signed-off-by: Colin Ian King <colin.king@...onical.com>
---
 drivers/char/agp/backend.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/char/agp/backend.c b/drivers/char/agp/backend.c
index 38ffb281df97..4e07f01833a2 100644
--- a/drivers/char/agp/backend.c
+++ b/drivers/char/agp/backend.c
@@ -121,7 +121,8 @@ static int agp_find_max(void)
 #endif
 	index = 1;
 
-	while ((memory > maxes_table[index].mem) && (index < 8))
+	while ((index < ARRAY_SIZE(maxes_table) - 1) &&
+	       (memory > maxes_table[index].mem))
 		index++;
 
 	result = maxes_table[index - 1].agp +
-- 
2.17.1