[PATCH] net: sock_diag: Fix spectre v1 gadget in __sock_diag_cmd()

[Jeremy Cline]

req->sdiag_family is a user-controlled value that's used as an array
index. Sanitize it after the bounds check to avoid speculative
out-of-bounds array access.

This also protects the sock_is_registered() call, so this removes the
sanitize call there.

Fixes: e978de7a6d38 ("net: socket: Fix potential spectre v1 gadget in sock_is_registered")
Cc: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
Cc: konrad.wilk@xxxxxxxxxx
Cc: jamie.iles@xxxxxxxxxx
Cc: liran.alon@xxxxxxxxxx
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Jeremy Cline <jcline@xxxxxxxxxx>
---

Since commit e978de7a6d38 didn't apply cleanly to v4.14, this won't
either since it reverts that change. To apply cleanly there, the change
to sock_is_registered() needs to be dropped.

 net/core/sock_diag.c | 2 ++
 net/socket.c         | 3 +--
 2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/net/core/sock_diag.c b/net/core/sock_diag.c
index c37b5be7c5e4..3312a5849a97 100644
--- a/net/core/sock_diag.c
+++ b/net/core/sock_diag.c
@@ -10,6 +10,7 @@
 #include <linux/kernel.h>
 #include <linux/tcp.h>
 #include <linux/workqueue.h>
+#include <linux/nospec.h>
 
 #include <linux/inet_diag.h>
 #include <linux/sock_diag.h>
@@ -218,6 +219,7 @@ static int __sock_diag_cmd(struct sk_buff *skb, struct nlmsghdr *nlh)
 
 	if (req->sdiag_family >= AF_MAX)
 		return -EINVAL;
+	req->sdiag_family = array_index_nospec(req->sdiag_family, AF_MAX);
 
 	if (sock_diag_handlers[req->sdiag_family] == NULL)
 		sock_load_diag_module(req->sdiag_family, 0);
diff --git a/net/socket.c b/net/socket.c
index 53c907169818..391a0da49ffe 100644
--- a/net/socket.c
+++ b/net/socket.c
@@ -2679,8 +2679,7 @@ EXPORT_SYMBOL(sock_unregister);
 
 bool sock_is_registered(int family)
 {
-	return family < NPROTO &&
-		rcu_access_pointer(net_families[array_index_nospec(family, NPROTO)]);
+	return family < NPROTO && rcu_access_pointer(net_families[family]);
 }
 
 static int __init sock_init(void)
-- 
2.17.1