netdev - [PATCH net] netlink: prevent potential spectre v1 gadgets

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Message-ID: <20230119110150.2678537-1-edumazet@google.com>
Date:   Thu, 19 Jan 2023 11:01:50 +0000
From:   Eric Dumazet <edumazet@...gle.com>
To:     "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>
Cc:     netdev@...r.kernel.org, eric.dumazet@...il.com,
        Eric Dumazet <edumazet@...gle.com>
Subject: [PATCH net] netlink: prevent potential spectre v1 gadgets

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@...gle.com>
---
 lib/nlattr.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/lib/nlattr.c b/lib/nlattr.c
index 9055e8b4d144e4c9fc0de6f6d8bbab0d7620932e..489e15bde5c1d248ba4914da2aa4839f1084f5b7 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);
-- 
2.39.1.405.gd4c25cc71f-goog