netdev - [PATCH 3/6] xfrm/compat: prevent potential spectre v1 gadget in xfrm_xlate32

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Message-ID: <20230208114322.266510-4-steffen.klassert@secunet.com>
Date:   Wed, 8 Feb 2023 12:43:19 +0100
From:   Steffen Klassert <steffen.klassert@...unet.com>
To:     David Miller <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>
CC:     Herbert Xu <herbert@...dor.apana.org.au>,
        Steffen Klassert <steffen.klassert@...unet.com>,
        <netdev@...r.kernel.org>
Subject: [PATCH 3/6] xfrm/compat: prevent potential spectre v1 gadget in xfrm_xlate32_attr()

From: Eric Dumazet <edumazet@...gle.com>

  int type = nla_type(nla);

  if (type > XFRMA_MAX) {
            return -EOPNOTSUPP;
  }

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

  if (nla_len(nla) < compat_policy[type].len) {

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

Fixes: 5106f4a8acff ("xfrm/compat: Add 32=>64-bit messages translator")
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
Cc: Dmitry Safonov <dima@...sta.com>
Cc: Steffen Klassert <steffen.klassert@...unet.com>
Reviewed-by: Dmitry Safonov <dima@...sta.com>
Signed-off-by: Steffen Klassert <steffen.klassert@...unet.com>
---
 net/xfrm/xfrm_compat.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/net/xfrm/xfrm_compat.c b/net/xfrm/xfrm_compat.c
index 12405aa5bce8..8cbf45a8bcdc 100644
--- a/net/xfrm/xfrm_compat.c
+++ b/net/xfrm/xfrm_compat.c
@@ -5,6 +5,7 @@
  * Based on code and translator idea by: Florian Westphal <fw@...len.de>
  */
 #include <linux/compat.h>
+#include <linux/nospec.h>
 #include <linux/xfrm.h>
 #include <net/xfrm.h>
 
@@ -437,6 +438,7 @@ static int xfrm_xlate32_attr(void *dst, const struct nlattr *nla,
 		NL_SET_ERR_MSG(extack, "Bad attribute");
 		return -EOPNOTSUPP;
 	}
+	type = array_index_nospec(type, XFRMA_MAX + 1);
 	if (nla_len(nla) < compat_policy[type].len) {
 		NL_SET_ERR_MSG(extack, "Attribute bad length");
 		return -EOPNOTSUPP;
-- 
2.34.1