From 45c8178cf69ea21b6d0356b3e541c8e111ba6458 Mon Sep 17 00:00:00 2001
From: Jeremy Cline <jcline@redhat.com>
Date: Fri, 27 Jul 2018 22:43:01 +0000
Subject: [PATCH] net: socket: fix potential spectre v1 gadget in socketcall

commit c8e8cd579bb4265651df8223730105341e61a2d1 upstream.

'call' is a user-controlled value, so sanitize the array index after the
bounds check to avoid speculating past the bounds of the 'nargs' array.

Found with the help of Smatch:

net/socket.c:2508 __do_sys_socketcall() warn: potential spectre issue
'nargs' [r] (local cap)

Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: stable@vger.kernel.org
Signed-off-by: Jeremy Cline <jcline@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 net/socket.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/net/socket.c b/net/socket.c
index 8b2bef6cfe42..d27922639a20 100644
--- a/net/socket.c
+++ b/net/socket.c
@@ -89,6 +89,7 @@
 #include <linux/magic.h>
 #include <linux/slab.h>
 #include <linux/xattr.h>
+#include <linux/nospec.h>
 
 #include <linux/uaccess.h>
 #include <asm/unistd.h>
@@ -2443,6 +2444,7 @@ SYSCALL_DEFINE2(socketcall, int, call, unsigned long __user *, args)
 
 	if (call < 1 || call > SYS_SENDMMSG)
 		return -EINVAL;
+	call = array_index_nospec(call, SYS_SENDMMSG + 1);
 
 	len = nargs[call];
 	if (len > sizeof(a))