[SRU][N][PATCH 6/6] rxrpc: Also unshare DATA/RESPONSE packets when paged frags are present

[Massimiliano Pellizzer]

From: Hyunwoo Kim <imv4bel at gmail.com>

commit aa54b1d27fe0c2b78e664a34fd0fdf7cd1960d71 upstream.

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.

Fixes: d0d5c0cd1e71 ("rxrpc: Use skb_unshare() rather than skb_cow_data()")
Cc: stable at vger.kernel.org
Signed-off-by: Hyunwoo Kim <imv4bel at gmail.com>
Reviewed-by: Jiayuan Chen <jiayuan.chen at linux.dev>
Acked-by: David Howells <dhowells at redhat.com>
Signed-off-by: Linus Torvalds <torvalds at linux-foundation.org>
Signed-off-by: Wentao Guan <guanwentao at uniontech.com>
Signed-off-by: Sasha Levin <sashal at kernel.org>
(cherry picked from commit 3711382a77342a9a1c3d2e7330dcfc7ea927f568 linux-6.12.y)
CVE-2026-43500
Signed-off-by: Massimiliano Pellizzer <massimiliano.pellizzer at canonical.com>
---
 net/rxrpc/call_event.c | 4 +++-
 net/rxrpc/conn_event.c | 3 ++-
 2 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/net/rxrpc/call_event.c b/net/rxrpc/call_event.c
index afd34aab6b9c1..3eb4c11f389e1 100644
--- a/net/rxrpc/call_event.c
+++ b/net/rxrpc/call_event.c
@@ -402,7 +402,9 @@ bool rxrpc_input_call_event(struct rxrpc_call *call, struct sk_buff *skb)
 
 		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 for
 			 * in-place decryption.
 			 */
diff --git a/net/rxrpc/conn_event.c b/net/rxrpc/conn_event.c
index 256101d9e2dd0..d289c38a77a85 100644
--- a/net/rxrpc/conn_event.c
+++ b/net/rxrpc/conn_event.c
@@ -231,7 +231,8 @@ 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.
 		 */
-- 
2.53.0