linux-kernel - [PATCH 5.4 070/104] netfilter: nft_osf: add missing check for DREG attribute

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Message-Id: <20200128135827.019998828@linuxfoundation.org>
Date:   Tue, 28 Jan 2020 15:00:31 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        syzbot+cf23983d697c26c34f60@...kaller.appspotmail.com,
        Florian Westphal <fw@...len.de>,
        Pablo Neira Ayuso <pablo@...filter.org>
Subject: [PATCH 5.4 070/104] netfilter: nft_osf: add missing check for DREG attribute

From: Florian Westphal <fw@...len.de>

commit 7eaecf7963c1c8f62d62c6a8e7c439b0e7f2d365 upstream.

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

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

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

--- a/net/netfilter/nft_osf.c
+++ b/net/netfilter/nft_osf.c
@@ -61,6 +61,9 @@ static int nft_osf_init(const struct nft
 	int err;
 	u8 ttl;
 
+	if (!tb[NFTA_OSF_DREG])
+		return -EINVAL;
+
 	if (tb[NFTA_OSF_TTL]) {
 		ttl = nla_get_u8(tb[NFTA_OSF_TTL]);
 		if (ttl > 2)