From: Jakob Koschel Date: Thu, 27 Jan 2022 14:44:04 +0000 (+0100) Subject: vt_ioctl: fix array_index_nospec in vt_setactivate X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=61cc70d9e8ef5b042d4ed87994d20100ec8896d9;p=linux.git 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. Co-developed-by: Brian Johannesmeyer Signed-off-by: Brian Johannesmeyer Signed-off-by: Jakob Koschel Link: https://lore.kernel.org/r/20220127144406.3589293-1-jakobkoschel@gmail.com Cc: stable Signed-off-by: Greg Kroah-Hartman --- diff --git a/drivers/tty/vt/vt_ioctl.c b/drivers/tty/vt/vt_ioctl.c index 3639bb6dc372e..e0714a9c9fd73 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) {