[PATCH net] rxrpc: Use skb_ensure_writable() before in-place decryption

[Hyunwoo Kim <imv4bel@gmail.com>]

Writing to any frag is incorrect since frag pages can be shared.
Use skb_ensure_writable() to ensure the skb is writable before
in-place decryption.

Fixes: aa54b1d27fe0 ("rxrpc: Also unshare DATA/RESPONSE packets when paged frags are present")
Signed-off-by: Hyunwoo Kim <imv4bel@gmail.com>
---
 net/rxrpc/call_event.c | 18 ++----------------
 net/rxrpc/conn_event.c | 23 +++++------------------
 2 files changed, 7 insertions(+), 34 deletions(-)

diff --git a/net/rxrpc/call_event.c b/net/rxrpc/call_event.c
index 2b19b252225e..837e121ed9a6 100644
--- a/net/rxrpc/call_event.c
+++ b/net/rxrpc/call_event.c
@@ -334,22 +334,8 @@ 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_has_frag_list(skb) ||
-			     skb_has_shared_frag(skb))) {
-				/* Unshare the packet so that it can be
-				 * modified by in-place decryption.
-				 */
-				struct sk_buff *nskb = skb_copy(skb, GFP_ATOMIC);
-
-				if (nskb) {
-					rxrpc_new_skb(nskb, rxrpc_skb_new_unshared);
-					rxrpc_input_call_packet(call, nskb);
-					rxrpc_free_skb(nskb, rxrpc_skb_put_call_rx);
-				} else {
-					/* OOM - Drop the packet. */
-					rxrpc_see_skb(skb, rxrpc_skb_see_unshare_nomem);
-				}
+			    skb_ensure_writable(skb, skb->len)) {
+				rxrpc_see_skb(skb, rxrpc_skb_see_unshare_nomem);
 			} else {
 				rxrpc_input_call_packet(call, skb);
 			}
diff --git a/net/rxrpc/conn_event.c b/net/rxrpc/conn_event.c
index 442414d90ba1..a9eaad970e0c 100644
--- a/net/rxrpc/conn_event.c
+++ b/net/rxrpc/conn_event.c
@@ -245,26 +245,13 @@ static int rxrpc_verify_response(struct rxrpc_connection *conn,
 {
 	int ret;
 
-	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.
-		 */
-		struct sk_buff *nskb = skb_copy(skb, GFP_NOFS);
-
-		if (nskb) {
-			rxrpc_new_skb(nskb, rxrpc_skb_new_unshared);
-			ret = conn->security->verify_response(conn, nskb);
-			rxrpc_free_skb(nskb, rxrpc_skb_put_response_copy);
-		} else {
-			/* OOM - Drop the packet. */
-			rxrpc_see_skb(skb, rxrpc_skb_see_unshare_nomem);
-			ret = -ENOMEM;
-		}
-	} else {
-		ret = conn->security->verify_response(conn, skb);
+	if (skb_ensure_writable(skb, skb->len)) {
+		rxrpc_see_skb(skb, rxrpc_skb_see_unshare_nomem);
+		return -ENOMEM;
 	}
 
+	ret = conn->security->verify_response(conn, skb);
+
 	return ret;
 }
 
-- 
2.43.0