linux-kernel - [PATCH 2/5] vt: fix unchecked __put

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Date:   Sat,  3 Jun 2017 09:35:06 +0200
From:   Adam Borowski <kilobyte@...band.pl>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jslaby@...e.com>, linux-kernel@...r.kernel.org
Cc:     Adam Borowski <kilobyte@...band.pl>, stable@...r.kernel.org,
        #@...ar.angband.pl, v3.7-@...ar.angband.pl
Subject: [PATCH 2/5] vt: fix unchecked __put_user() in tioclinux ioctls

Only read access is checked before this call.

Actually, at the moment this is not an issue, as every in-tree arch does
the same manual checks for VERIFY_READ vs VERIFY_WRITE, relying on the MMU
to tell them apart, but this wasn't the case in the past and may happen
again on some odd arch in the future.

If anyone cares about 3.7 and earlier, this is a security hole (untested)
on real 80386 CPUs.

Signed-off-by: Adam Borowski <kilobyte@...band.pl>
CC: stable@...r.kernel.org # v3.7-
---
 drivers/tty/vt/vt.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/tty/vt/vt.c b/drivers/tty/vt/vt.c
index 9309c7da660a..2ebaba16f785 100644
--- a/drivers/tty/vt/vt.c
+++ b/drivers/tty/vt/vt.c
@@ -2709,13 +2709,13 @@ int tioclinux(struct tty_struct *tty, unsigned long arg)
 	 * related to the kernel should not use this.
 	 */
 			data = vt_get_shift_state();
-			ret = __put_user(data, p);
+			ret = put_user(data, p);
 			break;
 		case TIOCL_GETMOUSEREPORTING:
 			console_lock();	/* May be overkill */
 			data = mouse_reporting();
 			console_unlock();
-			ret = __put_user(data, p);
+			ret = put_user(data, p);
 			break;
 		case TIOCL_SETVESABLANK:
 			console_lock();
@@ -2724,7 +2724,7 @@ int tioclinux(struct tty_struct *tty, unsigned long arg)
 			break;
 		case TIOCL_GETKMSGREDIRECT:
 			data = vt_get_kmsg_redirect();
-			ret = __put_user(data, p);
+			ret = put_user(data, p);
 			break;
 		case TIOCL_SETKMSGREDIRECT:
 			if (!capable(CAP_SYS_ADMIN)) {
-- 
2.11.0