FAILED: patch "[PATCH] rxrpc: Also unshare DATA/RESPONSE packets when paged frags" failed to apply to 5.15-stable tree

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 <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.15.y
git checkout FETCH_HEAD
git cherry-pick -x aa54b1d27fe0c2b78e664a34fd0fdf7cd1960d71
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2026051121-handcraft-joining-dbef@gregkh' --subject-prefix 'PATCH 5.15.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

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

From aa54b1d27fe0c2b78e664a34fd0fdf7cd1960d71 Mon Sep 17 00:00:00 2001
From: Hyunwoo Kim <[email protected]>
Date: Fri, 8 May 2026 17:53:09 +0900
Subject: [PATCH] rxrpc: Also unshare DATA/RESPONSE packets when paged frags
are present

The DATA-packet handler in rxrpc_input_call_event() and the RESPONSE handler in rxrpc_verify_response() copy the skb to a linear one before calling into the security ops only when skb_cloned() is true. An skb that is not cloned but still carries externally-owned paged fragments (e.g. SKBFL_SHARED_FRAG set by splice() into a UDP socket via __ip_append_data, or a chained skb_has_frag_list()) falls through to the in-place decryption path, which binds the frag pages directly into the AEAD/skcipher SGL via skb_to_sgvec().

Extend the gate to also unshare when skb_has_frag_list() or skb_has_shared_frag() is true. This catches the splice-loopback vector and other externally-shared frag sources while preserving the zero-copy fast path for skbs whose frags are kernel-private (e.g. NIC page_pool RX, GRO). The OOM/trace handling already in place is reused.

index fdd683261226..2b19b252225e 100644
@@ -334,7 +334,9 @@ bool rxrpc_input_call_event(struct rxrpc_call *call)
 
 			if (sp->hdr.type == RXRPC_PACKET_TYPE_DATA &&
 			    sp->hdr.securityIndex != 0 &&
-			    skb_cloned(skb)) {
+			    (skb_cloned(skb) ||
+			     skb_has_frag_list(skb) ||
+			     skb_has_shared_frag(skb))) {
 				/* Unshare the packet so that it can be
 				 * modified by in-place decryption.
 				 */

index a2130d25aaa9..442414d90ba1 100644
@@ -245,7 +245,8 @@ static int rxrpc_verify_response(struct rxrpc_connection *conn,
 {
 	int ret;
 
-	if (skb_cloned(skb)) {
+	if (skb_cloned(skb) || skb_has_frag_list(skb) ||
+	    skb_has_shared_frag(skb)) {
 		/* Copy the packet if shared so that we can do in-place
 		 * decryption.
 		 */