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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org,
        syzbot+cf23983d697c26c34f60@syzkaller.appspotmail.com,
        Florian Westphal <fw@strlen.de>,
        Pablo Neira Ayuso <pablo@netfilter.org>
Subject: [PATCH 4.19 39/92] netfilter: nft_osf: add missing check for DREG attribute
Date:   Tue, 28 Jan 2020 15:08:07 +0100
Message-Id: <20200128135814.094432237@linuxfoundation.org>
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From: Florian Westphal <fw@strlen.de>

commit 7eaecf7963c1c8f62d62c6a8e7c439b0e7f2d365 upstream.

syzbot reports just another NULL deref crash because of missing test
for presence of the attribute.

Reported-by: syzbot+cf23983d697c26c34f60@syzkaller.appspotmail.com
Fixes:  b96af92d6eaf9fadd ("netfilter: nf_tables: implement Passive OS fingerprint module in nft_osf")
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 net/netfilter/nft_osf.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/net/netfilter/nft_osf.c
+++ b/net/netfilter/nft_osf.c
@@ -47,6 +47,9 @@ static int nft_osf_init(const struct nft
 	struct nft_osf *priv = nft_expr_priv(expr);
 	int err;
 
+	if (!tb[NFTA_OSF_DREG])
+		return -EINVAL;
+
 	priv->dreg = nft_parse_register(tb[NFTA_OSF_DREG]);
 	err = nft_validate_register_store(ctx, priv->dreg, NULL,
 					  NFT_DATA_VALUE, NFT_OSF_MAXGENRELEN);