From 5ae656c7b83c576ae6f2801c05aaf3b6d08b0fb6 Mon Sep 17 00:00:00 2001
From: Eric Dumazet <eric.dumazet@gmail.com>
Date: Mon, 24 Oct 2011 01:52:35 -0400
Subject: [PATCH] --- yaml --- r: 266916 b: refs/heads/master c:
 ca35a0ef85e8ed6df6d5ab01fb6c3530cca0c469 h: refs/heads/master v: v3

---
 [refs]                  |  2 +-
 trunk/include/net/tcp.h |  2 +-
 trunk/net/ipv4/tcp.c    | 14 ++++++++------
 3 files changed, 10 insertions(+), 8 deletions(-)

diff --git a/[refs] b/[refs]
index a3b6f979a8c6..fb033684329e 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 01718e36df750670d0f840932a4d166522ead6c3
+refs/heads/master: ca35a0ef85e8ed6df6d5ab01fb6c3530cca0c469
diff --git a/trunk/include/net/tcp.h b/trunk/include/net/tcp.h
index 3edef0bebdd1..910cc29f9e97 100644
--- a/trunk/include/net/tcp.h
+++ b/trunk/include/net/tcp.h
@@ -1209,7 +1209,7 @@ extern void tcp_free_md5sig_pool(void);
 extern struct tcp_md5sig_pool	*tcp_get_md5sig_pool(void);
 extern void tcp_put_md5sig_pool(void);
 
-extern int tcp_md5_hash_header(struct tcp_md5sig_pool *, struct tcphdr *);
+extern int tcp_md5_hash_header(struct tcp_md5sig_pool *, const struct tcphdr *);
 extern int tcp_md5_hash_skb_data(struct tcp_md5sig_pool *, const struct sk_buff *,
 				 unsigned header_len);
 extern int tcp_md5_hash_key(struct tcp_md5sig_pool *hp,
diff --git a/trunk/net/ipv4/tcp.c b/trunk/net/ipv4/tcp.c
index 704adad8f07f..eefc61e3d0e4 100644
--- a/trunk/net/ipv4/tcp.c
+++ b/trunk/net/ipv4/tcp.c
@@ -2994,17 +2994,19 @@ void tcp_put_md5sig_pool(void)
 EXPORT_SYMBOL(tcp_put_md5sig_pool);
 
 int tcp_md5_hash_header(struct tcp_md5sig_pool *hp,
-			struct tcphdr *th)
+			const struct tcphdr *th)
 {
 	struct scatterlist sg;
+	struct tcphdr hdr;
 	int err;
 
-	__sum16 old_checksum = th->check;
-	th->check = 0;
+	/* We are not allowed to change tcphdr, make a local copy */
+	memcpy(&hdr, th, sizeof(hdr));
+	hdr.check = 0;
+
 	/* options aren't included in the hash */
-	sg_init_one(&sg, th, sizeof(struct tcphdr));
-	err = crypto_hash_update(&hp->md5_desc, &sg, sizeof(struct tcphdr));
-	th->check = old_checksum;
+	sg_init_one(&sg, &hdr, sizeof(hdr));
+	err = crypto_hash_update(&hp->md5_desc, &sg, sizeof(hdr));
 	return err;
 }
 EXPORT_SYMBOL(tcp_md5_hash_header);