netdev - [PATCH 1/2] net: socket: fix potential spectre v1 gadget in socketcall

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Message-Id: <20180727224302.5503-2-jcline@redhat.com>
Date:   Fri, 27 Jul 2018 22:43:01 +0000
From:   Jeremy Cline <jcline@...hat.com>
To:     "David S . Miller" <davem@...emloft.net>
Cc:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Jeremy Cline <jcline@...hat.com>, stable@...r.kernel.org
Subject: [PATCH 1/2] net: socket: fix potential spectre v1 gadget in socketcall

'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@...hat.com>
Cc: stable@...r.kernel.org
Signed-off-by: Jeremy Cline <jcline@...hat.com>
---
 net/socket.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/net/socket.c b/net/socket.c
index 3015ddace71e..f15d5cbb3ba4 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>
@@ -2504,6 +2505,7 @@ 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))
-- 
2.17.1