linux-kernel - [PATCH] video: hgafb: correctly handle card detect failure during probe

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Date:   Mon, 17 May 2021 00:57:14 +0530
From:   Anirudh Rayabharam <mail@...rudhrb.com>
To:     Ferenc Bakonyi <fero@...ma.obuda.kando.hu>,
        Igor Matheus Andrade Torrente <igormtorrente@...il.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     linux-kernel-mentees@...ts.linuxfoundation.org,
        Anirudh Rayabharam <mail@...rudhrb.com>,
        kernel test robot <oliver.sang@...el.com>,
        stable <stable@...r.kernel.org>,
        linux-nvidia@...ts.surfsouth.com, dri-devel@...ts.freedesktop.org,
        linux-fbdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] video: hgafb: correctly handle card detect failure during probe

The return value of hga_card_detect() is not properly handled causing
the probe to succeed even though hga_card_detect() failed. Since probe
succeeds, hgafb_open() can be called which will end up operating on an
unmapped hga_vram. This results in an out-of-bounds access as reported
by kernel test robot [1].

To fix this, correctly detect failure of hga_card_detect() by checking
for a non-zero error code.

[1]: https://lore.kernel.org/lkml/20210516150019.GB25903@xsang-OptiPlex-9020/

Reported-by: kernel test robot <oliver.sang@...el.com>
Fixes: dc13cac4862c ("video: hgafb: fix potential NULL pointer dereference")
Cc: stable <stable@...r.kernel.org>
Signed-off-by: Anirudh Rayabharam <mail@...rudhrb.com>
---
 drivers/video/fbdev/hgafb.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/video/fbdev/hgafb.c b/drivers/video/fbdev/hgafb.c
index cc8e62ae93f6..bd3d07aa4f0e 100644
--- a/drivers/video/fbdev/hgafb.c
+++ b/drivers/video/fbdev/hgafb.c
@@ -558,7 +558,7 @@ static int hgafb_probe(struct platform_device *pdev)
 	int ret;
 
 	ret = hga_card_detect();
-	if (!ret)
+	if (ret)
 		return ret;
 
 	printk(KERN_INFO "hgafb: %s with %ldK of memory detected.\n",
-- 
2.26.2