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From:   Mark Salyzyn <salyzyn@android.com>
To:     linux-kernel@vger.kernel.org
Cc:     kernel-team@android.com, Mark Salyzyn <salyzyn@android.com>,
        netdev@vger.kernel.org, "David S. Miller" <davem@davemloft.net>,
        Jakub Kicinski <kuba@kernel.org>, Thomas Graf <tgraf@suug.ch>
Subject: [PATCH] netlink: add buffer boundary checking
Date:   Thu, 23 Jul 2020 11:21:32 -0700
Message-Id: <20200723182136.2550163-1-salyzyn@android.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

Many of the nla_get_* inlines fail to check attribute's length before
copying the content resulting in possible out-of-boundary accesses.
Adjust the inlines to perform nla_len checking, for the most part
using the nla_memcpy function to faciliate since these are not
necessarily performance critical and do not need a likely fast path.

Signed-off-by: Mark Salyzyn <salyzyn@android.com>
Cc: netdev@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: kernel-team@android.com
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: Thomas Graf <tgraf@suug.ch>
Fixes: bfa83a9e03cf ("[NETLINK]: Type-safe netlink messages/attributes interface")
---
 include/net/netlink.h | 66 +++++++++++++++++++++++++++++++++++--------
 1 file changed, 54 insertions(+), 12 deletions(-)

diff --git a/include/net/netlink.h b/include/net/netlink.h
index c0411f14fb53..11c0f153be7c 100644
--- a/include/net/netlink.h
+++ b/include/net/netlink.h
@@ -1538,7 +1538,11 @@ static inline int nla_put_bitfield32(struct sk_buff *skb, int attrtype,
  */
 static inline u32 nla_get_u32(const struct nlattr *nla)
 {
-	return *(u32 *) nla_data(nla);
+	u32 tmp;
+
+	nla_memcpy(&tmp, nla, sizeof(tmp));
+
+	return tmp;
 }
 
 /**
@@ -1547,7 +1551,11 @@ static inline u32 nla_get_u32(const struct nlattr *nla)
  */
 static inline __be32 nla_get_be32(const struct nlattr *nla)
 {
-	return *(__be32 *) nla_data(nla);
+	__be32 tmp;
+
+	nla_memcpy(&tmp, nla, sizeof(tmp));
+
+	return tmp;
 }
 
 /**
@@ -1556,7 +1564,11 @@ static inline __be32 nla_get_be32(const struct nlattr *nla)
  */
 static inline __le32 nla_get_le32(const struct nlattr *nla)
 {
-	return *(__le32 *) nla_data(nla);
+	__le32 tmp;
+
+	nla_memcpy(&tmp, nla, sizeof(tmp));
+
+	return tmp;
 }
 
 /**
@@ -1565,7 +1577,11 @@ static inline __le32 nla_get_le32(const struct nlattr *nla)
  */
 static inline u16 nla_get_u16(const struct nlattr *nla)
 {
-	return *(u16 *) nla_data(nla);
+	u16 tmp;
+
+	nla_memcpy(&tmp, nla, sizeof(tmp));
+
+	return tmp;
 }
 
 /**
@@ -1574,7 +1590,11 @@ static inline u16 nla_get_u16(const struct nlattr *nla)
  */
 static inline __be16 nla_get_be16(const struct nlattr *nla)
 {
-	return *(__be16 *) nla_data(nla);
+	__be16 tmp;
+
+	nla_memcpy(&tmp, nla, sizeof(tmp));
+
+	return tmp;
 }
 
 /**
@@ -1583,7 +1603,11 @@ static inline __be16 nla_get_be16(const struct nlattr *nla)
  */
 static inline __le16 nla_get_le16(const struct nlattr *nla)
 {
-	return *(__le16 *) nla_data(nla);
+	__le16 tmp;
+
+	nla_memcpy(&tmp, nla, sizeof(tmp));
+
+	return tmp;
 }
 
 /**
@@ -1592,7 +1616,7 @@ static inline __le16 nla_get_le16(const struct nlattr *nla)
  */
 static inline u8 nla_get_u8(const struct nlattr *nla)
 {
-	return *(u8 *) nla_data(nla);
+	return (nla_len(nla) >= sizeof(u8)) ? *(u8 *) nla_data(nla) : 0;
 }
 
 /**
@@ -1627,7 +1651,11 @@ static inline __be64 nla_get_be64(const struct nlattr *nla)
  */
 static inline __le64 nla_get_le64(const struct nlattr *nla)
 {
-	return *(__le64 *) nla_data(nla);
+	__le64 tmp;
+
+	nla_memcpy(&tmp, nla, sizeof(tmp));
+
+	return tmp;
 }
 
 /**
@@ -1636,7 +1664,11 @@ static inline __le64 nla_get_le64(const struct nlattr *nla)
  */
 static inline s32 nla_get_s32(const struct nlattr *nla)
 {
-	return *(s32 *) nla_data(nla);
+	s32 tmp;
+
+	nla_memcpy(&tmp, nla, sizeof(tmp));
+
+	return tmp;
 }
 
 /**
@@ -1645,7 +1677,11 @@ static inline s32 nla_get_s32(const struct nlattr *nla)
  */
 static inline s16 nla_get_s16(const struct nlattr *nla)
 {
-	return *(s16 *) nla_data(nla);
+	s16 tmp;
+
+	nla_memcpy(&tmp, nla, sizeof(tmp));
+
+	return tmp;
 }
 
 /**
@@ -1654,7 +1690,7 @@ static inline s16 nla_get_s16(const struct nlattr *nla)
  */
 static inline s8 nla_get_s8(const struct nlattr *nla)
 {
-	return *(s8 *) nla_data(nla);
+	return (nla_len(nla) >= sizeof(s8)) ? *(s8 *) nla_data(nla) : 0;
 }
 
 /**
@@ -1698,7 +1734,11 @@ static inline unsigned long nla_get_msecs(const struct nlattr *nla)
  */
 static inline __be32 nla_get_in_addr(const struct nlattr *nla)
 {
-	return *(__be32 *) nla_data(nla);
+	__be32 tmp;
+
+	nla_memcpy(&tmp, nla, sizeof(tmp));
+
+	return tmp;
 }
 
 /**
@@ -1710,6 +1750,7 @@ static inline struct in6_addr nla_get_in6_addr(const struct nlattr *nla)
 	struct in6_addr tmp;
 
 	nla_memcpy(&tmp, nla, sizeof(tmp));
+
 	return tmp;
 }
 
@@ -1722,6 +1763,7 @@ static inline struct nla_bitfield32 nla_get_bitfield32(const struct nlattr *nla)
 	struct nla_bitfield32 tmp;
 
 	nla_memcpy(&tmp, nla, sizeof(tmp));
+
 	return tmp;
 }
 
-- 
2.28.0.rc0.105.gf9edc3c819-goog