Commit 1f274015 authored by David Howells's avatar David Howells Committed by Jakub Kicinski
Browse files

rxrpc: Fix potential UAF after skb_unshare() failure 

If skb_unshare() fails to unshare a packet due to allocation failure in
rxrpc_input_packet(), the skb pointer in the parent (rxrpc_io_thread())
will be NULL'd out.  This will likely cause the call to
trace_rxrpc_rx_done() to oops.

Fix this by moving the unsharing down to where rxrpc_input_call_event()
calls rxrpc_input_call_packet().  There are a number of places prior to
that where we ignore DATA packets for a variety of reasons (such as the
call already being complete) for which an unshare is then avoided.

And with that, rxrpc_input_packet() doesn't need to take a pointer to the
pointer to the packet, so change that to just a pointer.

Fixes: 2d1faf7a ("rxrpc: Simplify skbuff accounting in receive path")
Closes: https://sashiko.dev/#/patchset/20260408121252.2249051-1-dhowells%40redhat.com


Signed-off-by: default avatarDavid Howells <dhowells@redhat.com>
cc: Marc Dionne <marc.dionne@auristor.com>
cc: Jeffrey Altman <jaltman@auristor.com>
cc: Simon Horman <horms@kernel.org>
cc: linux-afs@lists.infradead.org
cc: stable@kernel.org
Link: https://patch.msgid.link/20260422161438.2593376-4-dhowells@redhat.com


Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
parent def304aa

include/trace/events/rxrpc.h

+2 −2
Original line number Diff line number Diff line
@@ -162,8 +162,6 @@ 
	E_(rxrpc_call_poke_timer_now,		"Timer-now")



#define rxrpc_skb_traces \

	EM(rxrpc_skb_eaten_by_unshare,		"ETN unshare  ") \

	EM(rxrpc_skb_eaten_by_unshare_nomem,	"ETN unshar-nm") \

	EM(rxrpc_skb_get_call_rx,		"GET call-rx  ") \

	EM(rxrpc_skb_get_conn_secured,		"GET conn-secd") \

	EM(rxrpc_skb_get_conn_work,		"GET conn-work") \
@@ -190,6 +188,7 @@ 
	EM(rxrpc_skb_put_purge,			"PUT purge    ") \

	EM(rxrpc_skb_put_purge_oob,		"PUT purge-oob") \

	EM(rxrpc_skb_put_response,		"PUT response ") \

	EM(rxrpc_skb_put_response_copy,		"PUT resp-cpy ") \

	EM(rxrpc_skb_put_rotate,		"PUT rotate   ") \

	EM(rxrpc_skb_put_unknown,		"PUT unknown  ") \

	EM(rxrpc_skb_see_conn_work,		"SEE conn-work") \
@@ -198,6 +197,7 @@ 
	EM(rxrpc_skb_see_recvmsg_oob,		"SEE recvm-oob") \

	EM(rxrpc_skb_see_reject,		"SEE reject   ") \

	EM(rxrpc_skb_see_rotate,		"SEE rotate   ") \

	EM(rxrpc_skb_see_unshare_nomem,		"SEE unshar-nm") \

	E_(rxrpc_skb_see_version,		"SEE version  ")



#define rxrpc_local_traces \

net/rxrpc/ar-internal.h

+0 −1
Original line number Diff line number Diff line
@@ -1486,7 +1486,6 @@ int rxrpc_server_keyring(struct rxrpc_sock *, sockptr_t, int); 
void rxrpc_kernel_data_consumed(struct rxrpc_call *, struct sk_buff *);

void rxrpc_new_skb(struct sk_buff *, enum rxrpc_skb_trace);

void rxrpc_see_skb(struct sk_buff *, enum rxrpc_skb_trace);

void rxrpc_eaten_skb(struct sk_buff *, enum rxrpc_skb_trace);

void rxrpc_get_skb(struct sk_buff *, enum rxrpc_skb_trace);

void rxrpc_free_skb(struct sk_buff *, enum rxrpc_skb_trace);

void rxrpc_purge_queue(struct sk_buff_head *);

net/rxrpc/call_event.c

+18 −1
Original line number Diff line number Diff line
@@ -332,7 +332,24 @@ bool rxrpc_input_call_event(struct rxrpc_call *call) 


			saw_ack |= sp->hdr.type == RXRPC_PACKET_TYPE_ACK;



			if (sp->hdr.securityIndex != 0 &&

			    skb_cloned(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);

				}

			} else {

				rxrpc_input_call_packet(call, skb);

			}

			rxrpc_free_skb(skb, rxrpc_skb_put_call_rx);

			did_receive = true;

		}

net/rxrpc/io_thread.c

+2 −22
Original line number Diff line number Diff line
@@ -192,13 +192,12 @@ static bool rxrpc_extract_abort(struct sk_buff *skb) 
/*

 * Process packets received on the local endpoint

 */

static bool rxrpc_input_packet(struct rxrpc_local *local, struct sk_buff **_skb)

static bool rxrpc_input_packet(struct rxrpc_local *local, struct sk_buff *skb)

{

	struct rxrpc_connection *conn;

	struct sockaddr_rxrpc peer_srx;

	struct rxrpc_skb_priv *sp;

	struct rxrpc_peer *peer = NULL;

	struct sk_buff *skb = *_skb;

	bool ret = false;



	skb_pull(skb, sizeof(struct udphdr));
@@ -244,25 +243,6 @@ static bool rxrpc_input_packet(struct rxrpc_local *local, struct sk_buff **_skb) 
			return rxrpc_bad_message(skb, rxrpc_badmsg_zero_call);

		if (sp->hdr.seq == 0)

			return rxrpc_bad_message(skb, rxrpc_badmsg_zero_seq);



		/* Unshare the packet so that it can be modified for in-place

		 * decryption.

		 */

		if (sp->hdr.securityIndex != 0) {

			skb = skb_unshare(skb, GFP_ATOMIC);

			if (!skb) {

				rxrpc_eaten_skb(*_skb, rxrpc_skb_eaten_by_unshare_nomem);

				*_skb = NULL;

				return just_discard;

			}



			if (skb != *_skb) {

				rxrpc_eaten_skb(*_skb, rxrpc_skb_eaten_by_unshare);

				*_skb = skb;

				rxrpc_new_skb(skb, rxrpc_skb_new_unshared);

				sp = rxrpc_skb(skb);

			}

		}

		break;



	case RXRPC_PACKET_TYPE_CHALLENGE:
@@ -494,7 +474,7 @@ int rxrpc_io_thread(void *data) 
			switch (skb->mark) {

			case RXRPC_SKB_MARK_PACKET:

				skb->priority = 0;

				if (!rxrpc_input_packet(local, &skb))

				if (!rxrpc_input_packet(local, skb))

					rxrpc_reject_packet(local, skb);

				trace_rxrpc_rx_done(skb->mark, skb->priority);

				rxrpc_free_skb(skb, rxrpc_skb_put_input);

net/rxrpc/skbuff.c

+0 −9
Original line number Diff line number Diff line
@@ -46,15 +46,6 @@ void rxrpc_get_skb(struct sk_buff *skb, enum rxrpc_skb_trace why) 
	skb_get(skb);

}



/*

 * Note the dropping of a ref on a socket buffer by the core.

 */

void rxrpc_eaten_skb(struct sk_buff *skb, enum rxrpc_skb_trace why)

{

	int n = atomic_inc_return(&rxrpc_n_rx_skbs);

	trace_rxrpc_skb(skb, 0, n, why);

}



/*

 * Note the destruction of a socket buffer.

 */