From e97267cb4d1ee01ca0929638ec0fcbb0904f903d Mon Sep 17 00:00:00 2001 From: "Gustavo A. R. Silva" Date: Thu, 16 Aug 2018 15:30:38 -0500 Subject: [PATCH] tty: vt_ioctl: fix potential Spectre v1 vsa.console is indirectly controlled by user-space, hence leading to a potential exploitation of the Spectre variant 1 vulnerability. This issue was detected with the help of Smatch: drivers/tty/vt/vt_ioctl.c:711 vt_ioctl() warn: potential spectre issue 'vc_cons' [r] Fix this by sanitizing vsa.console before using it to index vc_cons Notice that given that speculation windows are large, the policy is to kill the speculation on the first load and not worry if it can be completed with a dependent load/store [1]. [1] https://marc.info/?l=linux-kernel&m=152449131114778&w=2 Cc: stable@vger.kernel.org Signed-off-by: Gustavo A. R. Silva Reviewed-by: Alan Cox Signed-off-by: Greg Kroah-Hartman --- drivers/tty/vt/vt_ioctl.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/drivers/tty/vt/vt_ioctl.c b/drivers/tty/vt/vt_ioctl.c index a78ad10a119b..73cdc0d633dd 100644 --- a/drivers/tty/vt/vt_ioctl.c +++ b/drivers/tty/vt/vt_ioctl.c @@ -32,6 +32,8 @@ #include #include +#include + #include #include #include @@ -700,6 +702,8 @@ int vt_ioctl(struct tty_struct *tty, if (vsa.console == 0 || vsa.console > MAX_NR_CONSOLES) ret = -ENXIO; else { + vsa.console = array_index_nospec(vsa.console, + MAX_NR_CONSOLES + 1); vsa.console--; console_lock(); ret = vc_allocate(vsa.console);