From: Florian Westphal <fw@strlen.de>
To: Hyunwoo Kim <imv4bel@gmail.com>
Cc: pablo@netfilter.org, phil@nwl.cc, davem@davemloft.net,
edumazet@google.com, kuba@kernel.org, pabeni@redhat.com,
horms@kernel.org, netfilter-devel@vger.kernel.org,
coreteam@netfilter.org, netdev@vger.kernel.org
Subject: Re: [PATCH net] netfilter: ctnetlink: validate CTA_EXPECT_NAT_DIR to prevent OOB access
Date: Sat, 7 Mar 2026 19:01:07 +0100 [thread overview]
Message-ID: <aaxn41hrKcVo7e9M@strlen.de> (raw)
In-Reply-To: <aaxew8enOWT853XV@v4bel>
Hyunwoo Kim <imv4bel@gmail.com> wrote:
> ctnetlink_parse_expect_nat() assigns the user-supplied
> CTA_EXPECT_NAT_DIR value directly to exp->dir without validating that it
> is within the valid range (0 to IP_CT_DIR_MAX-1). When
> nf_nat_sip_expected() later uses exp->dir as an index into
> ct->master->tuplehash[], an out-of-bounds array access occurs.
>
> For example, with exp->dir = 100, the access at
> ct->master->tuplehash[100] reads 5600 bytes past the start of a
> 320-byte nf_conn object, causing a slab-out-of-bounds read confirmed by
> UBSAN.
>
> Validate exp->dir against IP_CT_DIR_MAX before accepting it.
I would prefer a fix for exp_nat_nla_policy so netlink policy validation
can handle this for us.
[CTA_EXPECT_NAT_DIR] = NLA_POLICY_MAX(NLA_BE32, IPCT_DIR_MAX),
.. should do it. Might make sense to check all other attrs while at it.
next prev parent reply other threads:[~2026-03-07 18:01 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-03-07 17:22 [PATCH net] netfilter: ctnetlink: validate CTA_EXPECT_NAT_DIR to prevent OOB access Hyunwoo Kim
2026-03-07 18:01 ` Florian Westphal [this message]
2026-03-08 10:42 ` Pablo Neira Ayuso
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