linux-kernel - [PATCH 4.19 56/56] drivers: video: fbcon: fix NULL dereference in fbcon

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Message-Id: <20210405085024.311723488@linuxfoundation.org>
Date:   Mon,  5 Apr 2021 10:54:27 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        syzbot+b67aaae8d3a927f68d20@...kaller.appspotmail.com,
        Du Cheng <ducheng2@...il.com>
Subject: [PATCH 4.19 56/56] drivers: video: fbcon: fix NULL dereference in fbcon_cursor()

From: Du Cheng <ducheng2@...il.com>

commit 01faae5193d6190b7b3aa93dae43f514e866d652 upstream.

add null-check on function pointer before dereference on ops->cursor

Reported-by: syzbot+b67aaae8d3a927f68d20@...kaller.appspotmail.com
Cc: stable <stable@...r.kernel.org>
Signed-off-by: Du Cheng <ducheng2@...il.com>
Link: https://lore.kernel.org/r/20210312081421.452405-1-ducheng2@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 drivers/video/fbdev/core/fbcon.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/drivers/video/fbdev/core/fbcon.c
+++ b/drivers/video/fbdev/core/fbcon.c
@@ -1306,6 +1306,9 @@ static void fbcon_cursor(struct vc_data
 
 	ops->cursor_flash = (mode == CM_ERASE) ? 0 : 1;
 
+	if (!ops->cursor)
+		return;
+
 	ops->cursor(vc, info, mode, get_color(vc, info, c, 1),
 		    get_color(vc, info, c, 0));
 }