From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, "Gustavo A. R. Silva" , Alan Cox Subject: [PATCH 4.14 50/64] tty: vt_ioctl: fix potential Spectre v1 Date: Thu, 27 Sep 2018 11:04:07 +0200 Message-Id: <20180927090256.998011927@linuxfoundation.org> In-Reply-To: <20180927090249.801943776@linuxfoundation.org> References: <20180927090249.801943776@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: 4.14-stable review patch. If anyone has any objections, please let me know. ------------------ From: Gustavo A. R. Silva commit e97267cb4d1ee01ca0929638ec0fcbb0904f903d upstream. 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(+) --- 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);