netdev - [PATCH net 4/4] netfilter: nfnetlink_osf: fix possible bogus match in nf_osf

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Message-Id: <20220908095757.1755-5-fw@strlen.de>
Date:   Thu,  8 Sep 2022 11:57:57 +0200
From:   Florian Westphal <fw@...len.de>
To:     <netdev@...r.kernel.org>
Cc:     Jakub Kicinski <kuba@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Paolo Abeni <pabeni@...hat.com>,
        <netfilter-devel@...r.kernel.org>,
        Pablo Neira Ayuso <pablo@...filter.org>,
        Florian Westphal <fw@...len.de>
Subject: [PATCH net 4/4] netfilter: nfnetlink_osf: fix possible bogus match in nf_osf_find()

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

nf_osf_find() incorrectly returns true on mismatch, this leads to
copying uninitialized memory area in nft_osf which can be used to leak
stale kernel stack data to userspace.

Fixes: 22c7652cdaa8 ("netfilter: nft_osf: Add version option support")
Signed-off-by: Pablo Neira Ayuso <pablo@...filter.org>
Signed-off-by: Florian Westphal <fw@...len.de>
---
 net/netfilter/nfnetlink_osf.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/net/netfilter/nfnetlink_osf.c b/net/netfilter/nfnetlink_osf.c
index 0fa2e2030427..ee6840bd5933 100644
--- a/net/netfilter/nfnetlink_osf.c
+++ b/net/netfilter/nfnetlink_osf.c
@@ -269,6 +269,7 @@ bool nf_osf_find(const struct sk_buff *skb,
 	struct nf_osf_hdr_ctx ctx;
 	const struct tcphdr *tcp;
 	struct tcphdr _tcph;
+	bool found = false;
 
 	memset(&ctx, 0, sizeof(ctx));
 
@@ -283,10 +284,11 @@ bool nf_osf_find(const struct sk_buff *skb,
 
 		data->genre = f->genre;
 		data->version = f->version;
+		found = true;
 		break;
 	}
 
-	return true;
+	return found;
 }
 EXPORT_SYMBOL_GPL(nf_osf_find);
 
-- 
2.35.1