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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,
        Ilja Van Sprundel <ivansprundel@ioactive.com>,
        Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>,
        "David S. Miller" <davem@davemloft.net>,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH 4.9 156/245] sctp: add size validation when walking chunks
Date:   Mon, 19 Jul 2021 16:51:38 +0200
Message-Id: <20210719144945.448079004@linuxfoundation.org>
In-Reply-To: <20210719144940.288257948@linuxfoundation.org>
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From: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>

[ Upstream commit 50619dbf8db77e98d821d615af4f634d08e22698 ]

The first chunk in a packet is ensured to be present at the beginning of
sctp_rcv(), as a packet needs to have at least 1 chunk. But the second
one, may not be completely available and ch->length can be over
uninitialized memory.

Fix here is by only trying to walk on the next chunk if there is enough to
hold at least the header, and then proceed with the ch->length validation
that is already there.

Reported-by: Ilja Van Sprundel <ivansprundel@ioactive.com>
Signed-off-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 net/sctp/input.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/sctp/input.c b/net/sctp/input.c
index 12d821ea8a1f..8f4574c4aa6c 100644
--- a/net/sctp/input.c
+++ b/net/sctp/input.c
@@ -1165,7 +1165,7 @@ static struct sctp_association *__sctp_rcv_walk_lookup(struct net *net,
 
 		ch = (sctp_chunkhdr_t *) ch_end;
 		chunk_num++;
-	} while (ch_end < skb_tail_pointer(skb));
+	} while (ch_end + sizeof(*ch) < skb_tail_pointer(skb));
 
 	return asoc;
 }
-- 
2.30.2