linux-kernel - [PATCH 2/2] vt_ioctl: add array_index_nospec to VT

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Date:   Thu, 27 Jan 2022 15:44:05 +0100
From:   Jakob Koschel <jakobkoschel@...il.com>
To:     linux-kernel@...r.kernel.org
Cc:     Brian Johannesmeyer <bjohannesmeyer@...il.com>,
        Cristiano Giuffrida <c.giuffrida@...nl>,
        "Gustavo A. R. Silva" <gustavo@...eddedor.com>,
        "Bos, H.J." <h.j.bos@...nl>, Thomas Gleixner <tglx@...utronix.de>,
        Jakob Koschel <jakobkoschel@...il.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jirislaby@...nel.org>,
        "Maciej W. Rozycki" <macro@...am.me.uk>,
        "Ahmed S. Darwish" <a.darwish@...utronix.de>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Subject: [PATCH 2/2] vt_ioctl: add array_index_nospec to VT_ACTIVATE

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>
---
 drivers/tty/vt/vt_ioctl.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/tty/vt/vt_ioctl.c b/drivers/tty/vt/vt_ioctl.c
index e0714a9c9fd7..58013698635f 100644
--- a/drivers/tty/vt/vt_ioctl.c
+++ b/drivers/tty/vt/vt_ioctl.c
@@ -845,6 +845,7 @@ int vt_ioctl(struct tty_struct *tty,
 			return -ENXIO;

 		arg--;
+		arg = array_index_nospec(arg, MAX_NR_CONSOLES);
 		console_lock();
 		ret = vc_allocate(arg);
 		console_unlock();
--
2.25.1