linux-kernel - [PATCH 2/2] vt_ioctl: change VT_RESIZEX ioctl to check for error return from vc

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Date:   Fri, 31 Jul 2020 12:33:12 -0400
From:   George Kennedy <george.kennedy@...cle.com>
To:     george.kennedy@...cle.com, gregkh@...uxfoundation.org,
        jirislaby@...nel.org, b.zolnierkie@...sung.com,
        linux-fbdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        dan.carpenter@...cle.com, dhaval.giani@...cle.com
Subject: [PATCH 2/2] vt_ioctl: change VT_RESIZEX ioctl to check for error return from vc_resize()

vc_resize() can return with an error after failure. Change VT_RESIZEX ioctl
to save struct vc_data values that are modified and restore the original
values in case of error.

Signed-off-by: George Kennedy <george.kennedy@...cle.com>
Reported-by: syzbot+38a3699c7eaf165b97a6@...kaller.appspotmail.com
---
Version of patch available for Mainline also.

 drivers/tty/vt/vt_ioctl.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/drivers/tty/vt/vt_ioctl.c b/drivers/tty/vt/vt_ioctl.c
index 91c3017..a4e520b 100644
--- a/drivers/tty/vt/vt_ioctl.c
+++ b/drivers/tty/vt/vt_ioctl.c
@@ -806,12 +806,22 @@ static int vt_resizex(struct vc_data *vc, struct vt_consize __user *cs)
 		console_lock();
 		vcp = vc_cons[i].d;
 		if (vcp) {
+			int ret;
+			int save_scan_lines = vcp->vc_scan_lines;
+			int save_font_height = vcp->vc_font.height;
+
 			if (v.v_vlin)
 				vcp->vc_scan_lines = v.v_vlin;
 			if (v.v_clin)
 				vcp->vc_font.height = v.v_clin;
 			vcp->vc_resize_user = 1;
-			vc_resize(vcp, v.v_cols, v.v_rows);
+			ret = vc_resize(vcp, v.v_cols, v.v_rows);
+			if (ret) {
+				vcp->vc_scan_lines = save_scan_lines;
+				vcp->vc_font.height = save_font_height;
+				console_unlock();
+				return ret;
+			}
 		}
 		console_unlock();
 	}
-- 
1.8.3.1