tcp: md5: dont write skb head in tcp_md5_hash_header()
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>
Signed-off-by: David S. Miller <davem@davemloft.net>
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 @@
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);