From 61cc70d9e8ef5b042d4ed87994d20100ec8896d9 Mon Sep 17 00:00:00 2001
From: Jakob Koschel <jakobkoschel@gmail.com>
Date: Thu, 27 Jan 2022 15:44:04 +0100
Subject: [PATCH] vt_ioctl: fix array_index_nospec in vt_setactivate
Git-commit: 61cc70d9e8ef5b042d4ed87994d20100ec8896d9
Patch-mainline: v5.17-rc4
References: git-fixes
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.
Co-developed-by: Brian Johannesmeyer <bjohannesmeyer@gmail.com>
Signed-off-by: Brian Johannesmeyer <bjohannesmeyer@gmail.com>
Signed-off-by: Jakob Koschel <jakobkoschel@gmail.com>
Link: https://lore.kernel.org/r/20220127144406.3589293-1-jakobkoschel@gmail.com
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Acked-by: Takashi Iwai <tiwai@suse.de>
---
drivers/tty/vt/vt_ioctl.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/tty/vt/vt_ioctl.c b/drivers/tty/vt/vt_ioctl.c
index 3639bb6dc372..e0714a9c9fd7 100644
--- a/drivers/tty/vt/vt_ioctl.c
+++ b/drivers/tty/vt/vt_ioctl.c
@@ -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) {
--
2.31.1