patch "vt_ioctl: fix array_index_nospec in vt_setactivate" added to tty-linus

This is a note to let you know that I've just added the patch titled

vt_ioctl: fix array_index_nospec in vt_setactivate

to my tty git tree which can be found at
git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty.git
in the tty-linus branch.

The patch will show up in the next release of the linux-next tree (usually sometime within the next 24 hours during the week.)

The patch will hopefully also be merged in Linus's tree for the next -rc kernel release.

If you have any questions about this process, please let me know.

From 61cc70d9e8ef5b042d4ed87994d20100ec8896d9 Mon Sep 17 00:00:00 2001
From: Jakob Koschel <[email protected]>
Date: Thu, 27 Jan 2022 15:44:04 +0100
Subject: vt_ioctl: fix array_index_nospec in vt_setactivate

array_index_nospec ensures that an out-of-bounds value is set to zero on the transient path. Decreasing the value by one afterwards causes a transient integer underflow. vsa.console should be decreased first and then sanitized with array_index_nospec.

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

---
 drivers/tty/vt/vt_ioctl.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

index 3639bb6dc372..e0714a9c9fd7 100644
@@ -599,8 +599,8 @@ static int vt_setactivate(struct vt_setactivate __user *sa)
 	if (vsa.console == 0 || vsa.console > MAX_NR_CONSOLES)
 		return -ENXIO;
 
-	vsa.console = array_index_nospec(vsa.console, MAX_NR_CONSOLES + 1);
 	vsa.console--;
+	vsa.console = array_index_nospec(vsa.console, MAX_NR_CONSOLES);
 	console_lock();
 	ret = vc_allocate(vsa.console);
 	if (ret) {

2.35.1