linux-kernel - [PATCH 4.9 23/34] vt_ioctl: add array_index_nospec to VT

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Message-Id: <20220214092446.692735054@linuxfoundation.org>
Date:   Mon, 14 Feb 2022 10:25:49 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Brian Johannesmeyer <bjohannesmeyer@...il.com>,
        Jakob Koschel <jakobkoschel@...il.com>
Subject: [PATCH 4.9 23/34] vt_ioctl: add array_index_nospec to VT_ACTIVATE

From: Jakob Koschel <jakobkoschel@...il.com>

commit 28cb138f559f8c1a1395f5564f86b8bbee83631b upstream.

in vt_setactivate an almost identical code path has been patched
with array_index_nospec. In the VT_ACTIVATE path the user input
is from a system call argument instead of a usercopy.
For consistency both code paths should have the same mitigations
applied.

Kasper Acknowledgements: Jakob Koschel, Brian Johannesmeyer, Kaveh
Razavi, Herbert Bos, Cristiano Giuffrida from the VUSec group at VU
Amsterdam.

Co-developed-by: Brian Johannesmeyer <bjohannesmeyer@...il.com>
Signed-off-by: Brian Johannesmeyer <bjohannesmeyer@...il.com>
Signed-off-by: Jakob Koschel <jakobkoschel@...il.com>
Link: https://lore.kernel.org/r/20220127144406.3589293-2-jakobkoschel@gmail.com
Cc: stable <stable@...r.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 drivers/tty/vt/vt_ioctl.c |    1 +
 1 file changed, 1 insertion(+)

--- a/drivers/tty/vt/vt_ioctl.c
+++ b/drivers/tty/vt/vt_ioctl.c
@@ -694,6 +694,7 @@ int vt_ioctl(struct tty_struct *tty,
 			ret =  -ENXIO;
 		else {
 			arg--;
+			arg = array_index_nospec(arg, MAX_NR_CONSOLES);
 			console_lock();
 			ret = vc_allocate(arg);
 			console_unlock();