From: "Gustavo A. R. Silva" <gustavo@embeddedor.com>
To: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Jiri Slaby <jslaby@suse.com>
Cc: linux-kernel@vger.kernel.org,
"Gustavo A. R. Silva" <gustavo@embeddedor.com>
Subject: [PATCH] tty: vt_ioctl: fix potential Spectre v1
Date: Thu, 16 Aug 2018 15:30:38 -0500 [thread overview]
Message-ID: <20180816203038.GA14399@embeddedor.com> (raw)
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 <gustavo@embeddedor.com>
---
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 a78ad10..73cdc0d 100644
--- a/drivers/tty/vt/vt_ioctl.c
+++ b/drivers/tty/vt/vt_ioctl.c
@@ -32,6 +32,8 @@
#include <asm/io.h>
#include <linux/uaccess.h>
+#include <linux/nospec.h>
+
#include <linux/kbd_kern.h>
#include <linux/vt_kern.h>
#include <linux/kbd_diacr.h>
@@ -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);
--
2.7.4
next reply other threads:[~2018-08-16 20:30 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-08-16 20:30 Gustavo A. R. Silva [this message]
2018-08-17 11:07 ` [PATCH] tty: vt_ioctl: fix potential Spectre v1 Alan Cox
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