From f0950402e8c76e7dcb08563f1b4e8000fbc62455 Mon Sep 17 00:00:00 2001
From: Eric Dumazet <edumazet@google.com>
Date: Thu, 19 Jan 2023 11:01:50 +0000
Subject: [PATCH] netlink: prevent potential spectre v1 gadgets
Git-commit: f0950402e8c76e7dcb08563f1b4e8000fbc62455
Patch-mainline: v6.2-rc6
References: bsc#1209547 CVE-2017-5753 

Most netlink attributes are parsed and validated from
__nla_validate_parse() or validate_nla()

    u16 type = nla_type(nla);

    if (type == 0 || type > maxtype) {
        /* error or continue */
    }

@type is then used as an array index and can be used
as a Spectre v1 gadget.

array_index_nospec() can be used to prevent leaking
content of kernel memory to malicious users.

This should take care of vast majority of netlink uses,
but an audit is needed to take care of others where
validation is not yet centralized in core netlink functions.

Fixes: bfa83a9e03cf ("[NETLINK]: Type-safe netlink messages/attributes interface")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Link: https://lore.kernel.org/r/20230119110150.2678537-1-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Oliver Neukum <oneukum@suse.com>
---
 lib/nlattr.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/lib/nlattr.c b/lib/nlattr.c
index 9055e8b4d144..489e15bde5c1 100644
--- a/lib/nlattr.c
+++ b/lib/nlattr.c
@@ -10,6 +10,7 @@
 #include <linux/kernel.h>
 #include <linux/errno.h>
 #include <linux/jiffies.h>
+#include <linux/nospec.h>
 #include <linux/skbuff.h>
 #include <linux/string.h>
 #include <linux/types.h>
@@ -381,6 +382,7 @@ static int validate_nla(const struct nlattr *nla, int maxtype,
 	if (type <= 0 || type > maxtype)
 		return 0;
 
+	type = array_index_nospec(type, maxtype + 1);
 	pt = &policy[type];
 
 	BUG_ON(pt->type > NLA_TYPE_MAX);
@@ -596,6 +598,7 @@ static int __nla_validate_parse(const struct nlattr *head, int len, int maxtype,
 			}
 			continue;
 		}
+		type = array_index_nospec(type, maxtype + 1);
 		if (policy) {
 			int err = validate_nla(nla, maxtype, policy,
 					       validate, extack, depth);
-- 
2.40.0