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From:   Ben Hutchings <ben@decadent.org.uk>
To:     linux-kernel@vger.kernel.org, stable@vger.kernel.org
CC:     akpm@linux-foundation.org, "Josh Poimboeuf" <jpoimboe@redhat.com>,
        "David S. Miller" <davem@davemloft.net>,
        "Jeremy Cline" <jcline@redhat.com>
Date:   Sun, 11 Nov 2018 19:49:05 +0000
Message-ID: <lsq.1541965745.632796283@decadent.org.uk>
Subject: [PATCH 3.16 300/366] net: socket: fix potential spectre v1 gadget
 in socketcall
In-Reply-To: <lsq.1541965744.387173642@decadent.org.uk>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

3.16.61-rc1 review patch.  If anyone has any objections, please let me know.

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

From: Jeremy Cline <jcline@redhat.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@redhat.com>
Signed-off-by: Jeremy Cline <jcline@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
 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>
@@ -2494,6 +2495,7 @@ 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))