netdev - [PATCH net 2/4] sctp: add size validation when walking chunks

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Message-Id: <1f204ae1a2b2dfe6ea49fd9fdd583a4d02a70542.1624904195.git.marcelo.leitner@gmail.com>
Date:   Mon, 28 Jun 2021 16:13:42 -0300
From:   Marcelo Ricardo Leitner <marcelo.leitner@...il.com>
To:     netdev@...r.kernel.org
Cc:     linux-sctp@...r.kernel.org,
        Ilja Van Sprundel <ivansprundel@...ctive.com>,
        Neil Horman <nhorman@...driver.com>,
        Vlad Yasevich <vyasevich@...il.com>,
        Xin Long <lucien.xin@...il.com>
Subject: [PATCH net 2/4] sctp: add size validation when walking chunks

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@...ctive.com>
Signed-off-by: Marcelo Ricardo Leitner <marcelo.leitner@...il.com>
---
 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 8924e2e142c8234dac233e56e923110e266c9834..f72bff93745c44be0dbfa29e754f2872a7d874c2 100644
--- a/net/sctp/input.c
+++ b/net/sctp/input.c
@@ -1247,7 +1247,7 @@ static struct sctp_association *__sctp_rcv_walk_lookup(struct net *net,
 
 		ch = (struct sctp_chunkhdr *)ch_end;
 		chunk_num++;
-	} while (ch_end < skb_tail_pointer(skb));
+	} while (ch_end + sizeof(*ch) < skb_tail_pointer(skb));
 
 	return asoc;
 }
-- 
2.31.1