linux-kernel - [PATCH] crypto: chtls - use after free in chtls_pt

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Message-ID: <20180601075852.fn5hongkasesi2ep@kili.mountain>
Date:   Fri, 1 Jun 2018 10:59:25 +0300
From:   Dan Carpenter <dan.carpenter@...cle.com>
To:     Harsh Jain <harsh@...lsio.com>, Atul Gupta <atul.gupta@...lsio.com>
Cc:     Herbert Xu <herbert@...dor.apana.org.au>,
        "David S. Miller" <davem@...emloft.net>,
        Atul Gupta <atul.gupta@...lsio.com>,
        Michael Werner <werner@...lsio.com>,
        linux-crypto@...r.kernel.org, linux-kernel@...r.kernel.org,
        kernel-janitors@...r.kernel.org
Subject: [PATCH] crypto: chtls - use after free in chtls_pt_recvmsg()

We call chtls_free_skb() but then we dereference it on the next lines.
Also "skb" can't be NULL, we just dereferenced it on the line before.

I have moved the free down a couple lines to fix this issue.

Fixes: 17a7d24aa89d ("crypto: chtls - generic handling of data and hdr")
Signed-off-by: Dan Carpenter <dan.carpenter@...cle.com>

diff --git a/drivers/crypto/chelsio/chtls/chtls_io.c b/drivers/crypto/chelsio/chtls/chtls_io.c
index 51fc6821cbbf..708e232e3cdf 100644
--- a/drivers/crypto/chelsio/chtls/chtls_io.c
+++ b/drivers/crypto/chelsio/chtls/chtls_io.c
@@ -1548,15 +1548,14 @@ static int chtls_pt_recvmsg(struct sock *sk, struct msghdr *msg, size_t len,
 			tp->urg_data = 0;
 
 		if ((avail + offset) >= skb->len) {
-			if (likely(skb))
-				chtls_free_skb(sk, skb);
-			buffers_freed++;
 			if (ULP_SKB_CB(skb)->flags & ULPCB_FLAG_TLS_HDR) {
 				tp->copied_seq += skb->len;
 				hws->rcvpld = skb->hdr_len;
 			} else {
 				tp->copied_seq += hws->rcvpld;
 			}
+			chtls_free_skb(sk, skb);
+			buffers_freed++;
 			hws->copied_seq = 0;
 			if (copied >= target &&
 			    !skb_peek(&sk->sk_receive_queue))