[PATCH 6.12 v2 2/2] rxrpc: Also unshare DATA/RESPONSE packets when paged frags are present

[Wentao Guan <guanwentao@uniontech.com>]

From: Hyunwoo Kim <imv4bel@gmail.com>

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@vger.kernel.org
Signed-off-by: Hyunwoo Kim <imv4bel@gmail.com>
Reviewed-by: Jiayuan Chen <jiayuan.chen@linux.dev>
Acked-by: David Howells <dhowells@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
(cherry picked from commit aa54b1d27fe0c2b78e664a34fd0fdf7cd1960d71)
Signed-off-by: Wentao Guan <guanwentao@uniontech.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 62ddaa129ce5a..fda16b39e8e73 100644
--- a/net/rxrpc/call_event.c
+++ b/net/rxrpc/call_event.c
@@ -347,7 +347,9 @@ 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 6dcfaed1f7485..3a58fb9210383 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.
 		 */
-- 
2.30.2