linux-kernel - [PATCH] fbcon: Fix a NULL pointer dereference issue in fbcon

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Message-Id: <20240916011027.303875-1-qianqiang.liu@163.com>
Date: Mon, 16 Sep 2024 09:10:28 +0800
From: Qianqiang Liu <qianqiang.liu@....com>
To: aniel@...ll.ch,
	deller@....de,
	gregkh@...uxfoundation.org,
	linux-kernel@...r.kernel.org
Cc: linux-fbdev@...r.kernel.org,
	dri-devel@...ts.freedesktop.org,
	Qianqiang Liu <qianqiang.liu@....com>,
	stable@...r.kernel.org,
	syzbot+3d613ae53c031502687a@...kaller.appspotmail.com
Subject: [PATCH] fbcon: Fix a NULL pointer dereference issue in fbcon_putcs

syzbot has found a NULL pointer dereference bug in fbcon [1].

This issue is caused by ops->putcs being a NULL pointer.
We need to check the pointer before using it.

[1] https://syzkaller.appspot.com/bug?extid=3d613ae53c031502687a

Cc: stable@...r.kernel.org
Reported-and-tested-by: syzbot+3d613ae53c031502687a@...kaller.appspotmail.com
Signed-off-by: Qianqiang Liu <qianqiang.liu@....com>
---
 drivers/video/fbdev/core/fbcon.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/video/fbdev/core/fbcon.c b/drivers/video/fbdev/core/fbcon.c
index 3f7333dca508..96c1262cc981 100644
--- a/drivers/video/fbdev/core/fbcon.c
+++ b/drivers/video/fbdev/core/fbcon.c
@@ -1284,7 +1284,7 @@ static void fbcon_putcs(struct vc_data *vc, const u16 *s, unsigned int count,
 	struct fbcon_display *p = &fb_display[vc->vc_num];
 	struct fbcon_ops *ops = info->fbcon_par;
 
-	if (!fbcon_is_inactive(vc, info))
+	if (!fbcon_is_inactive(vc, info) && ops->putcs)
 		ops->putcs(vc, info, s, count, real_y(p, ypos), xpos,
 			   get_color(vc, info, scr_readw(s), 1),
 			   get_color(vc, info, scr_readw(s), 0));
-- 
2.39.2