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From:   Ben Hutchings <ben@decadent.org.uk>
To:     linux-kernel@vger.kernel.org, stable@vger.kernel.org
CC:     akpm@linux-foundation.org, Denis Kirjanov <kda@linux-powerpc.org>,
        "Pablo Neira Ayuso" <pablo@netfilter.org>
Date:   Fri, 24 Apr 2020 00:04:58 +0100
Message-ID: <lsq.1587683028.38144236@decadent.org.uk>
Subject: [PATCH 3.16 071/245] netfilter: nf_tables: missing sanitization
 in data from userspace
In-Reply-To: <lsq.1587683027.831233700@decadent.org.uk>
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3.16.83-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Pablo Neira Ayuso <pablo@netfilter.org>

commit 71df14b0ce094be46d105b5a3ededd83b8e779a0 upstream.

Do not assume userspace always sends us NFT_DATA_VALUE for bitwise and
cmp expressions. Although NFT_DATA_VERDICT does not make any sense, it
is still possible to handcraft a netlink message using this incorrect
data type.

Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
 net/netfilter/nft_bitwise.c | 19 ++++++++++++++-----
 net/netfilter/nft_cmp.c     | 12 ++++++++++--
 2 files changed, 24 insertions(+), 7 deletions(-)

--- a/net/netfilter/nft_bitwise.c
+++ b/net/netfilter/nft_bitwise.c
@@ -86,16 +86,25 @@ static int nft_bitwise_init(const struct
 	err = nft_data_init(NULL, &priv->mask, &d1, tb[NFTA_BITWISE_MASK]);
 	if (err < 0)
 		return err;
-	if (d1.len != priv->len)
-		return -EINVAL;
+	if (d1.len != priv->len) {
+		err = -EINVAL;
+		goto err1;
+	}
 
 	err = nft_data_init(NULL, &priv->xor, &d2, tb[NFTA_BITWISE_XOR]);
 	if (err < 0)
-		return err;
-	if (d2.len != priv->len)
-		return -EINVAL;
+		goto err1;
+	if (d2.len != priv->len) {
+		err = -EINVAL;
+		goto err2;
+	}
 
 	return 0;
+err2:
+	nft_data_uninit(&priv->xor, d2.type);
+err1:
+	nft_data_uninit(&priv->mask, d1.type);
+	return err;
 }
 
 static int nft_bitwise_dump(struct sk_buff *skb, const struct nft_expr *expr)
--- a/net/netfilter/nft_cmp.c
+++ b/net/netfilter/nft_cmp.c
@@ -201,10 +201,18 @@ nft_cmp_select_ops(const struct nft_ctx
 	if (err < 0)
 		return ERR_PTR(err);
 
+	if (desc.type != NFT_DATA_VALUE) {
+		err = -EINVAL;
+		goto err1;
+	}
+
 	if (desc.len <= sizeof(u32) && op == NFT_CMP_EQ)
 		return &nft_cmp_fast_ops;
-	else
-		return &nft_cmp_ops;
+
+	return &nft_cmp_ops;
+err1:
+	nft_data_uninit(&data, desc.type);
+	return ERR_PTR(-EINVAL);
 }
 
 static struct nft_expr_type nft_cmp_type __read_mostly = {