linux-kernel - [PATCH 4.9 27/32] net: socket: fix potential spectre v1 gadget in socketcall

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Message-Id: <20180804082651.284127864@linuxfoundation.org>
Date:   Sat,  4 Aug 2018 11:01:17 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Josh Poimboeuf <jpoimboe@...hat.com>,
        Jeremy Cline <jcline@...hat.com>,
        "David S. Miller" <davem@...emloft.net>
Subject: [PATCH 4.9 27/32] net: socket: fix potential spectre v1 gadget in socketcall

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Jeremy Cline <jcline@...hat.com>

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@...hat.com>
Cc: stable@...r.kernel.org
Signed-off-by: Jeremy Cline <jcline@...hat.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 net/socket.c |    2 ++
 1 file changed, 2 insertions(+)

--- 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 <asm/uaccess.h>
 #include <asm/unistd.h>
@@ -2338,6 +2339,7 @@ SYSCALL_DEFINE2(socketcall, int, call, u
 
 	if (call < 1 || call > SYS_SENDMMSG)
 		return -EINVAL;
+	call = array_index_nospec(call, SYS_SENDMMSG + 1);
 
 	len = nargs[call];
 	if (len > sizeof(a))