FAILED: patch "[PATCH] mptcp: introduce MAPPING_BAD_CSUM" failed to apply to 5.15-stable tree

FAILED: patch "[PATCH] mptcp: introduce MAPPING_BAD_CSUM" failed to apply to 5.15-stable tree

[gregkh]

The patch below does not apply to the 5.15-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 31bf11de146c3f8892093ff39f8f9b3069d6a852 Mon Sep 17 00:00:00 2001
From: Paolo Abeni <pabeni@redhat.com>
Date: Mon, 27 Jun 2022 18:02:36 -0700
Subject: [PATCH] mptcp: introduce MAPPING_BAD_CSUM

This allow moving a couple of conditional out of the fast path,
making the code more easy to follow and will simplify the next
patch.

Fixes: ae66fb2ba6c3 ("mptcp: Do TCP fallback on early DSS checksum failure")
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/net/mptcp/subflow.c b/net/mptcp/subflow.c
index 50ad19adc003..42a7c18a1c24 100644
--- a/net/mptcp/subflow.c
+++ b/net/mptcp/subflow.c
@@ -843,7 +843,8 @@ enum mapping_status {
 	MAPPING_INVALID,
 	MAPPING_EMPTY,
 	MAPPING_DATA_FIN,
-	MAPPING_DUMMY
+	MAPPING_DUMMY,
+	MAPPING_BAD_CSUM
 };
 
 static void dbg_bad_map(struct mptcp_subflow_context *subflow, u32 ssn)
@@ -958,9 +959,7 @@ static enum mapping_status validate_data_csum(struct sock *ssk, struct sk_buff *
 				 subflow->map_data_csum);
 	if (unlikely(csum)) {
 		MPTCP_INC_STATS(sock_net(ssk), MPTCP_MIB_DATACSUMERR);
-		if (subflow->mp_join || subflow->valid_csum_seen)
-			subflow->send_mp_fail = 1;
-		return subflow->mp_join ? MAPPING_INVALID : MAPPING_DUMMY;
+		return MAPPING_BAD_CSUM;
 	}
 
 	subflow->valid_csum_seen = 1;
@@ -1182,10 +1181,8 @@ static bool subflow_check_data_avail(struct sock *ssk)
 
 		status = get_mapping_status(ssk, msk);
 		trace_subflow_check_data_avail(status, skb_peek(&ssk->sk_receive_queue));
-		if (unlikely(status == MAPPING_INVALID))
-			goto fallback;
-
-		if (unlikely(status == MAPPING_DUMMY))
+		if (unlikely(status == MAPPING_INVALID || status == MAPPING_DUMMY ||
+			     status == MAPPING_BAD_CSUM))
 			goto fallback;
 
 		if (status != MAPPING_OK)
@@ -1227,7 +1224,10 @@ static bool subflow_check_data_avail(struct sock *ssk)
 fallback:
 	if (!__mptcp_check_fallback(msk)) {
 		/* RFC 8684 section 3.7. */
-		if (subflow->send_mp_fail) {
+		if (status == MAPPING_BAD_CSUM &&
+		    (subflow->mp_join || subflow->valid_csum_seen)) {
+			subflow->send_mp_fail = 1;
+
 			if (!READ_ONCE(msk->allow_infinite_fallback)) {
 				ssk->sk_err = EBADMSG;
 				tcp_set_state(ssk, TCP_CLOSE);