Patchwork [net-next] tcp: md5: dont write skb head in tcp_md5_hash_header()

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Submitter Eric Dumazet
Date Oct. 21, 2011, 12:01 p.m.
Message ID <1319198495.2338.34.camel@edumazet-HP-Compaq-6005-Pro-SFF-PC>
Download mbox | patch
Permalink /patch/120989/
State Accepted
Delegated to: David Miller
Headers show

Comments

Eric Dumazet - Oct. 21, 2011, 12:01 p.m.
tcp_md5_hash_header() writes into skb header a temporary zero value,
this might confuse other users of this area.

Since tcphdr is small (20 bytes), copy it in a temporary variable and
make the change in the copy.

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
---
 include/net/tcp.h |    2 +-
 net/ipv4/tcp.c    |   14 ++++++++------
 2 files changed, 9 insertions(+), 7 deletions(-)



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Patch

diff --git a/include/net/tcp.h b/include/net/tcp.h
index 3edef0b..910cc29 100644
--- a/include/net/tcp.h
+++ b/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/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 704adad..eefc61e 100644
--- a/net/ipv4/tcp.c
+++ b/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);