x86/kprobes: Fix crash when probing CS CALL instructionsgrafted

When using eBPF to probe CS CALL instructions within a function,
a crash can be triggered.

The eBPF tool probes offset 257 of the __hrtimer_run_queues()
function:

<__hrtimer_run_queues+249>:  nopl   0x0(%rax,%rax,1)
<__hrtimer_run_queues+254>:  mov    %r14,%rdi
<__hrtimer_run_queues+257>:  cs call <__x86_indirect_thunk_r12>
<__hrtimer_run_queues+263>:  mov    %eax,%r12d
<__hrtimer_run_queues+266>:  xchg   %ax,%ax
<__hrtimer_run_queues+268>:  mov    %r13,%rdi

Which triggers this crash:

  BUG: unable to handle page fault for address: 00000000000f41c9
  #PF: supervisor write access in kernel mode
  #PF: error_code(0x0002) - not-present page
  PGD 0 P4D 0
  Oops: 0002 [#1] SMP NOPTI
  CPU: 1 PID: 0 Comm: swapper/1 Kdump: loaded Tainted: P
  RIP: 0010:__hrtimer_run_queues+0x106/0x230

Note that __hrtimer_run_queues+0x106 is __hrtimer_run_queues+262, which is
at the 6th byte of the above CS CALL instruction. Since the CS CALL
instruction occupies 6 bytes, the exception occurred in the middle of that
call instruction.

The root cause is that when using eBPF tools to probe in the middle of a
function, a kprobe with INT3 is used as the underlying implementation.

During single-step emulation of the original CALL instruction,
int3_emulate_call() assumes that the probed CALL instruction is 5 bytes
long. However, the actual CS-prefixed CALL instruction occupies 6 bytes,
so it constructs an incorrect exception return address. When the CPU
returns from the kprobe handler, the next instruction to be executed is at
the address of the last byte of that CS CALL instruction. Coincidentally,
starting from that address, the CPU fetches and decodes a completely
different instruction, which ultimately triggers a kernel crash.

Fix the issue by using the actual instruction length obtained from
the instruction decoder when constructing the exception return
address, rather than relying on the hardcoded CALL_INSN_SIZE macro.

[ mingo: Refined the changelog ]

Fixes: 6256e668b7af ("x86/kprobes: Use int3 instead of debug trap for single-step")
Suggested-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Jinke Han <jinkehan@didiglobal.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Acked-by: Yafang Shao <laoar.shao@gmail.com>
Acked-by: Borislav Petkov <bp@alien8.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://patch.msgid.link/20260908073742.GA10517@didi-ThinkCentre-M920t-N000

1 files changed, 996 insertions, 0 deletions

diff --git a/fs/afs/rxrpc.c b/fs/afs/rxrpc.c
new file mode 100644
index 000000000..d82916657
--- /dev/null
+++ b/fs/afs/rxrpc.c
@@ -0,0 +1,996 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/* Maintain an RxRPC server socket to do AFS communications through
+ *
+ * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ */
+
+#include <linux/slab.h>
+#include <linux/sched/signal.h>
+
+#include <net/sock.h>
+#include <net/af_rxrpc.h>
+#include "internal.h"
+#include "afs_cm.h"
+#include "protocol_yfs.h"
+#define RXRPC_TRACE_ONLY_DEFINE_ENUMS
+#include <trace/events/rxrpc.h>
+
+struct workqueue_struct *afs_async_calls;
+
+static void afs_deferred_free_worker(struct work_struct *work);
+static void afs_wake_up_call_waiter(struct sock *, struct rxrpc_call *, unsigned long);
+static void afs_wake_up_async_call(struct sock *, struct rxrpc_call *, unsigned long);
+static void afs_process_async_call(struct work_struct *);
+static void afs_rx_new_call(struct sock *, struct rxrpc_call *, unsigned long);
+static void afs_rx_discard_new_call(struct rxrpc_call *, unsigned long);
+static void afs_rx_attach(struct rxrpc_call *rxcall, unsigned long user_call_ID);
+static void afs_rx_notify_oob(struct sock *sk, struct sk_buff *oob);
+static int afs_deliver_cm_op_id(struct afs_call *);
+
+static const struct rxrpc_kernel_ops afs_rxrpc_callback_ops = {
+	.notify_new_call	= afs_rx_new_call,
+	.discard_new_call	= afs_rx_discard_new_call,
+	.user_attach_call	= afs_rx_attach,
+	.notify_oob		= afs_rx_notify_oob,
+};
+
+/* asynchronous incoming call initial processing */
+static const struct afs_call_type afs_RXCMxxxx = {
+	.name		= "CB.xxxx",
+	.deliver	= afs_deliver_cm_op_id,
+};
+
+/*
+ * open an RxRPC socket and bind it to be a server for callback notifications
+ * - the socket is left in blocking mode and non-blocking ops use MSG_DONTWAIT
+ */
+int afs_open_socket(struct afs_net *net)
+{
+	struct sockaddr_rxrpc srx;
+	struct socket *socket;
+	int ret;
+
+	_enter("");
+
+	ret = sock_create_kern(net->net, AF_RXRPC, SOCK_DGRAM, PF_INET6, &socket);
+	if (ret < 0)
+		goto error_1;
+
+	socket->sk->sk_allocation = GFP_NOFS;
+	socket->sk->sk_user_data = net;
+
+	/* bind the callback manager's address to make this a server socket */
+	memset(&srx, 0, sizeof(srx));
+	srx.srx_family			= AF_RXRPC;
+	srx.srx_service			= CM_SERVICE;
+	srx.transport_type		= SOCK_DGRAM;
+	srx.transport_len		= sizeof(srx.transport.sin6);
+	srx.transport.sin6.sin6_family	= AF_INET6;
+	srx.transport.sin6.sin6_port	= htons(AFS_CM_PORT);
+
+	ret = rxrpc_sock_set_min_security_level(socket->sk,
+						RXRPC_SECURITY_ENCRYPT);
+	if (ret < 0)
+		goto error_2;
+
+	ret = rxrpc_sock_set_manage_response(socket->sk, true);
+	if (ret < 0)
+		goto error_2;
+
+	ret = afs_create_token_key(net, socket);
+	if (ret < 0)
+		pr_err("Couldn't create RxGK CM key: %d\n", ret);
+
+	ret = kernel_bind(socket, (struct sockaddr_unsized *) &srx, sizeof(srx));
+	if (ret == -EADDRINUSE) {
+		srx.transport.sin6.sin6_port = 0;
+		ret = kernel_bind(socket, (struct sockaddr_unsized *) &srx, sizeof(srx));
+	}
+	if (ret < 0)
+		goto error_2;
+
+	srx.srx_service = YFS_CM_SERVICE;
+	ret = kernel_bind(socket, (struct sockaddr_unsized *) &srx, sizeof(srx));
+	if (ret < 0)
+		goto error_2;
+
+	/* Ideally, we'd turn on service upgrade here, but we can't because
+	 * OpenAFS is buggy and leaks the userStatus field from packet to
+	 * packet and between FS packets and CB packets - so if we try to do an
+	 * upgrade on an FS packet, OpenAFS will leak that into the CB packet
+	 * it sends back to us.
+	 */
+
+	rxrpc_kernel_set_notifications(socket, &afs_rxrpc_callback_ops);
+
+	ret = kernel_listen(socket, INT_MAX);
+	if (ret < 0)
+		goto error_2;
+
+	net->socket = socket;
+	afs_charge_preallocation(&net->charge_preallocation_work);
+	_leave(" = 0");
+	return 0;
+
+error_2:
+	sock_release(socket);
+error_1:
+	_leave(" = %d", ret);
+	return ret;
+}
+
+/*
+ * close the RxRPC socket AFS was using
+ */
+void afs_close_socket(struct afs_net *net)
+{
+	_enter("");
+
+	cancel_work_sync(&net->charge_preallocation_work);
+	cancel_work_sync(&net->rx_oob_work);
+	/* Future work items should now see ->live is false. */
+
+	kernel_listen(net->socket, 0);
+
+	/* Make sure work items are no longer running. */
+	flush_workqueue(afs_async_calls);
+	cancel_work_sync(&net->charge_preallocation_work);
+
+	if (net->spare_incoming_call) {
+		afs_put_call(net->spare_incoming_call);
+		net->spare_incoming_call = NULL;
+	}
+
+	_debug("outstanding %u", atomic_read(&net->nr_outstanding_calls));
+	wait_var_event(&net->nr_outstanding_calls,
+		       !atomic_read(&net->nr_outstanding_calls));
+	_debug("no outstanding calls");
+
+	kernel_sock_shutdown(net->socket, SHUT_RDWR);
+	flush_workqueue(afs_async_calls);
+	cancel_work_sync(&net->rx_oob_work);
+	net->socket->sk->sk_user_data = NULL;
+	sock_release(net->socket);
+	key_put(net->fs_cm_token_key);
+
+	_debug("dework");
+	_leave("");
+}
+
+/*
+ * Allocate a call.
+ */
+static struct afs_call *afs_alloc_call(struct afs_net *net,
+				       const struct afs_call_type *type,
+				       gfp_t gfp)
+{
+	struct afs_call *call;
+	int o;
+
+	call = kzalloc_obj(*call, gfp);
+	if (!call)
+		return NULL;
+
+	call->type = type;
+	call->net = net;
+	call->debug_id = atomic_inc_return(&rxrpc_debug_id);
+	refcount_set(&call->ref, 1);
+	INIT_WORK(&call->async_work, type->async_rx ?: afs_process_async_call);
+	INIT_WORK(&call->work, call->type->work);
+	INIT_WORK(&call->free_work, afs_deferred_free_worker);
+	init_waitqueue_head(&call->waitq);
+	spin_lock_init(&call->state_lock);
+	call->iter = &call->def_iter;
+
+	o = atomic_inc_return(&net->nr_outstanding_calls);
+	trace_afs_call(call->debug_id, afs_call_trace_alloc, 1, o,
+		       __builtin_return_address(0));
+	return call;
+}
+
+static void afs_free_call(struct afs_call *call)
+{
+	struct afs_net *net = call->net;
+	int o;
+
+	ASSERT(!work_pending(&call->async_work));
+
+	rxrpc_kernel_put_peer(call->peer);
+
+	if (call->rxcall) {
+		rxrpc_kernel_shutdown_call(net->socket, call->rxcall);
+		rxrpc_kernel_put_call(net->socket, call->rxcall);
+		call->rxcall = NULL;
+	}
+	if (call->type->destructor)
+		call->type->destructor(call);
+
+	afs_unuse_server_notime(call->net, call->server, afs_server_trace_unuse_call);
+	kfree(call->request);
+
+	o = atomic_read(&net->nr_outstanding_calls);
+	trace_afs_call(call->debug_id, afs_call_trace_free, 0, o,
+		       __builtin_return_address(0));
+	kfree(call);
+
+	o = atomic_dec_return(&net->nr_outstanding_calls);
+	if (o == 0)
+		wake_up_var(&net->nr_outstanding_calls);
+}
+
+/*
+ * Dispose of a reference on a call.
+ */
+void afs_put_call(struct afs_call *call)
+{
+	struct afs_net *net = call->net;
+	unsigned int debug_id = call->debug_id;
+	bool zero;
+	int r, o;
+
+	zero = __refcount_dec_and_test(&call->ref, &r);
+	o = atomic_read(&net->nr_outstanding_calls);
+	trace_afs_call(debug_id, afs_call_trace_put, r - 1, o,
+		       __builtin_return_address(0));
+	if (zero)
+		afs_free_call(call);
+}
+
+static void afs_deferred_free_worker(struct work_struct *work)
+{
+	struct afs_call *call = container_of(work, struct afs_call, free_work);
+
+	afs_free_call(call);
+}
+
+/*
+ * Dispose of a reference on a call, deferring the cleanup to a workqueue
+ * to avoid lock recursion.
+ */
+void afs_deferred_put_call(struct afs_call *call)
+{
+	struct afs_net *net = call->net;
+	unsigned int debug_id = call->debug_id;
+	bool zero;
+	int r, o;
+
+	zero = __refcount_dec_and_test(&call->ref, &r);
+	o = atomic_read(&net->nr_outstanding_calls);
+	trace_afs_call(debug_id, afs_call_trace_put, r - 1, o,
+		       __builtin_return_address(0));
+	if (zero)
+		schedule_work(&call->free_work);
+}
+
+/*
+ * Queue the call for actual work.
+ */
+static void afs_queue_call_work(struct afs_call *call)
+{
+	if (call->type->work) {
+		afs_get_call(call, afs_call_trace_work);
+		if (!queue_work(afs_wq, &call->work))
+			afs_put_call(call);
+	}
+}
+
+/*
+ * allocate a call with flat request and reply buffers
+ */
+struct afs_call *afs_alloc_flat_call(struct afs_net *net,
+				     const struct afs_call_type *type,
+				     size_t request_size, size_t reply_max)
+{
+	struct afs_call *call;
+
+	call = afs_alloc_call(net, type, GFP_NOFS);
+	if (!call)
+		goto nomem_call;
+
+	if (request_size) {
+		call->request_size = request_size;
+		call->request = kmalloc(request_size, GFP_NOFS);
+		if (!call->request)
+			goto nomem_free;
+	}
+
+	if (reply_max) {
+		call->reply_max = reply_max;
+		call->buffer = kmalloc(reply_max, GFP_NOFS);
+		if (!call->buffer)
+			goto nomem_free;
+	}
+
+	afs_extract_to_buf(call, call->reply_max);
+	call->operation_ID = type->op;
+	init_waitqueue_head(&call->waitq);
+	return call;
+
+nomem_free:
+	afs_put_call(call);
+nomem_call:
+	return NULL;
+}
+
+/*
+ * clean up a call with flat buffer
+ */
+void afs_flat_call_destructor(struct afs_call *call)
+{
+	_enter("");
+
+	kfree(call->request);
+	call->request = NULL;
+	kfree(call->buffer);
+	call->buffer = NULL;
+}
+
+/*
+ * Advance the AFS call state when the RxRPC call ends the transmit phase.
+ */
+static void afs_notify_end_request_tx(struct sock *sock,
+				      struct rxrpc_call *rxcall,
+				      unsigned long call_user_ID)
+{
+	struct afs_call *call = (struct afs_call *)call_user_ID;
+
+	afs_set_call_state(call, AFS_CALL_CL_REQUESTING, AFS_CALL_CL_AWAIT_REPLY);
+}
+
+/*
+ * Initiate a call and synchronously queue up the parameters for dispatch.  Any
+ * error is stored into the call struct, which the caller must check for.
+ */
+void afs_make_call(struct afs_call *call, gfp_t gfp)
+{
+	struct rxrpc_call *rxcall;
+	struct msghdr msg;
+	struct kvec iov[1];
+	size_t len;
+	s64 tx_total_len;
+	int ret;
+
+	_enter(",{%pISp+%u},", rxrpc_kernel_remote_addr(call->peer), call->service_id);
+
+	ASSERT(call->type != NULL);
+	ASSERT(call->type->name != NULL);
+
+	_debug("____MAKE %p{%s,%x} [%d]____",
+	       call, call->type->name, key_serial(call->key),
+	       atomic_read(&call->net->nr_outstanding_calls));
+
+	trace_afs_make_call(call);
+
+	/* Work out the length we're going to transmit.  This is awkward for
+	 * calls such as FS.StoreData where there's an extra injection of data
+	 * after the initial fixed part.
+	 */
+	tx_total_len = call->request_size;
+	if (call->write_iter)
+		tx_total_len += iov_iter_count(call->write_iter);
+
+	/* If the call is going to be asynchronous, we need an extra ref for
+	 * the call to hold itself so the caller need not hang on to its ref.
+	 */
+	if (call->async) {
+		afs_get_call(call, afs_call_trace_get);
+		call->drop_ref = true;
+	}
+
+	/* create a call */
+	rxcall = rxrpc_kernel_begin_call(call->net->socket, call->peer, call->key,
+					 (unsigned long)call,
+					 tx_total_len,
+					 call->max_lifespan,
+					 gfp,
+					 (call->async ?
+					  afs_wake_up_async_call :
+					  afs_wake_up_call_waiter),
+					 call->service_id,
+					 call->upgrade,
+					 (call->intr ? RXRPC_PREINTERRUPTIBLE :
+					  RXRPC_UNINTERRUPTIBLE),
+					 call->debug_id);
+	if (IS_ERR(rxcall)) {
+		ret = PTR_ERR(rxcall);
+		call->error = ret;
+		goto error_kill_call;
+	}
+
+	call->rxcall = rxcall;
+	call->issue_time = ktime_get_real();
+
+	/* send the request */
+	iov[0].iov_base	= call->request;
+	iov[0].iov_len	= call->request_size;
+
+	msg.msg_name		= NULL;
+	msg.msg_namelen		= 0;
+	iov_iter_kvec(&msg.msg_iter, ITER_SOURCE, iov, 1, call->request_size);
+	msg.msg_control		= NULL;
+	msg.msg_controllen	= 0;
+	msg.msg_flags		= MSG_WAITALL | (call->write_iter ? MSG_MORE : 0);
+
+	ret = rxrpc_kernel_send_data(call->net->socket, rxcall,
+				     &msg, call->request_size,
+				     afs_notify_end_request_tx);
+	if (ret < 0)
+		goto error_do_abort;
+
+	if (call->write_iter) {
+		msg.msg_iter = *call->write_iter;
+		msg.msg_flags &= ~MSG_MORE;
+		trace_afs_send_data(call, &msg);
+
+		ret = rxrpc_kernel_send_data(call->net->socket,
+					     call->rxcall, &msg,
+					     iov_iter_count(&msg.msg_iter),
+					     afs_notify_end_request_tx);
+		*call->write_iter = msg.msg_iter;
+
+		trace_afs_sent_data(call, &msg, ret);
+		if (ret < 0)
+			goto error_do_abort;
+	}
+
+	/* Note that at this point, we may have received the reply or an abort
+	 * - and an asynchronous call may already have completed.
+	 *
+	 * afs_wait_for_call_to_complete(call)
+	 * must be called to synchronously clean up.
+	 */
+	return;
+
+error_do_abort:
+	if (ret != -ECONNABORTED)
+		rxrpc_kernel_abort_call(call->net->socket, rxcall,
+					RX_USER_ABORT, ret,
+					afs_abort_send_data_error);
+	if (call->async) {
+		afs_see_call(call, afs_call_trace_async_abort);
+		return;
+	}
+
+	if (ret == -ECONNABORTED) {
+		len = 0;
+		iov_iter_kvec(&msg.msg_iter, ITER_DEST, NULL, 0, 0);
+		rxrpc_kernel_recv_data(call->net->socket, rxcall,
+				       &msg.msg_iter, &len, false,
+				       &call->abort_code, &call->service_id);
+		call->responded = true;
+	}
+	call->error = ret;
+	trace_afs_call_done(call);
+error_kill_call:
+	if (call->async)
+		afs_see_call(call, afs_call_trace_async_kill);
+	if (call->type->immediate_cancel)
+		call->type->immediate_cancel(call);
+
+	/* We need to dispose of the extra ref we grabbed for an async call.
+	 * The call, however, might be queued on afs_async_calls and we need to
+	 * make sure we don't get any more notifications that might requeue it.
+	 */
+	if (call->rxcall)
+		rxrpc_kernel_shutdown_call(call->net->socket, call->rxcall);
+	if (call->async) {
+		if (cancel_work_sync(&call->async_work))
+			afs_put_call(call);
+		afs_set_call_complete(call, ret, 0);
+	}
+
+	call->error = ret;
+	call->state = AFS_CALL_COMPLETE;
+	_leave(" = %d", ret);
+}
+
+/*
+ * Log remote abort codes that indicate that we have a protocol disagreement
+ * with the server.
+ */
+static void afs_log_error(struct afs_call *call, s32 remote_abort)
+{
+	static int max = 0;
+	const char *msg;
+	int m;
+
+	switch (remote_abort) {
+	case RX_EOF:		 msg = "unexpected EOF";	break;
+	case RXGEN_CC_MARSHAL:	 msg = "client marshalling";	break;
+	case RXGEN_CC_UNMARSHAL: msg = "client unmarshalling";	break;
+	case RXGEN_SS_MARSHAL:	 msg = "server marshalling";	break;
+	case RXGEN_SS_UNMARSHAL: msg = "server unmarshalling";	break;
+	case RXGEN_DECODE:	 msg = "opcode decode";		break;
+	case RXGEN_SS_XDRFREE:	 msg = "server XDR cleanup";	break;
+	case RXGEN_CC_XDRFREE:	 msg = "client XDR cleanup";	break;
+	case -32:		 msg = "insufficient data";	break;
+	default:
+		return;
+	}
+
+	m = max;
+	if (m < 3) {
+		max = m + 1;
+		pr_notice("kAFS: Peer reported %s failure on %s [%pISp]\n",
+			  msg, call->type->name,
+			  rxrpc_kernel_remote_addr(call->peer));
+	}
+}
+
+/*
+ * deliver messages to a call
+ */
+void afs_deliver_to_call(struct afs_call *call)
+{
+	enum afs_call_state state;
+	size_t len;
+	u32 abort_code, remote_abort = 0;
+	int ret;
+
+	_enter("%s", call->type->name);
+
+	while (state = READ_ONCE(call->state),
+	       state == AFS_CALL_CL_AWAIT_REPLY ||
+	       state == AFS_CALL_SV_AWAIT_OP_ID ||
+	       state == AFS_CALL_SV_AWAIT_REQUEST ||
+	       state == AFS_CALL_SV_AWAIT_ACK
+	       ) {
+		if (state == AFS_CALL_SV_AWAIT_ACK) {
+			len = 0;
+			iov_iter_kvec(&call->def_iter, ITER_DEST, NULL, 0, 0);
+			ret = rxrpc_kernel_recv_data(call->net->socket,
+						     call->rxcall, &call->def_iter,
+						     &len, false, &remote_abort,
+						     &call->service_id);
+			trace_afs_receive_data(call, &call->def_iter, false, ret);
+
+			if (ret == -EINPROGRESS || ret == -EAGAIN)
+				return;
+			if (ret < 0 || ret == 1) {
+				if (ret == 1)
+					ret = 0;
+				goto call_complete;
+			}
+			return;
+		}
+
+		ret = call->type->deliver(call);
+		state = READ_ONCE(call->state);
+		if (ret == 0 && call->unmarshalling_error)
+			ret = -EBADMSG;
+		switch (ret) {
+		case 0:
+			call->responded = true;
+			afs_queue_call_work(call);
+			if (state == AFS_CALL_CL_PROC_REPLY) {
+				if (call->op)
+					set_bit(AFS_SERVER_FL_MAY_HAVE_CB,
+						&call->op->server->flags);
+				goto call_complete;
+			}
+			ASSERTCMP(state, >, AFS_CALL_CL_PROC_REPLY);
+			goto done;
+		case -EINPROGRESS:
+		case -EAGAIN:
+			goto out;
+		case -ECONNABORTED:
+			ASSERTCMP(state, ==, AFS_CALL_COMPLETE);
+			call->responded = true;
+			afs_log_error(call, call->abort_code);
+			goto done;
+		case -ENOTSUPP:
+			call->responded = true;
+			abort_code = RXGEN_OPCODE;
+			rxrpc_kernel_abort_call(call->net->socket, call->rxcall,
+						abort_code, ret,
+						afs_abort_op_not_supported);
+			goto local_abort;
+		case -EIO:
+			pr_err("kAFS: Call %u in bad state %u\n",
+			       call->debug_id, state);
+			fallthrough;
+		case -ENODATA:
+		case -EBADMSG:
+		case -EMSGSIZE:
+		case -ENOMEM:
+		case -EFAULT:
+			abort_code = RXGEN_CC_UNMARSHAL;
+			if (state != AFS_CALL_CL_AWAIT_REPLY)
+				abort_code = RXGEN_SS_UNMARSHAL;
+			rxrpc_kernel_abort_call(call->net->socket, call->rxcall,
+						abort_code, ret,
+						afs_abort_unmarshal_error);
+			goto local_abort;
+		default:
+			abort_code = RX_CALL_DEAD;
+			rxrpc_kernel_abort_call(call->net->socket, call->rxcall,
+						abort_code, ret,
+						afs_abort_general_error);
+			goto local_abort;
+		}
+	}
+
+done:
+	if (call->type->done)
+		call->type->done(call);
+out:
+	_leave("");
+	return;
+
+local_abort:
+	abort_code = 0;
+call_complete:
+	afs_set_call_complete(call, ret, remote_abort);
+	goto done;
+}
+
+/*
+ * Wait synchronously for a call to complete.
+ */
+void afs_wait_for_call_to_complete(struct afs_call *call)
+{
+	bool rxrpc_complete = false;
+
+	_enter("");
+
+	if (!afs_check_call_state(call, AFS_CALL_COMPLETE)) {
+		DECLARE_WAITQUEUE(myself, current);
+
+		add_wait_queue(&call->waitq, &myself);
+		for (;;) {
+			set_current_state(TASK_UNINTERRUPTIBLE);
+
+			/* deliver any messages that are in the queue */
+			if (!afs_check_call_state(call, AFS_CALL_COMPLETE) &&
+			    call->need_attention) {
+				call->need_attention = false;
+				__set_current_state(TASK_RUNNING);
+				afs_deliver_to_call(call);
+				continue;
+			}
+
+			if (afs_check_call_state(call, AFS_CALL_COMPLETE))
+				break;
+
+			if (!rxrpc_kernel_check_life(call->net->socket, call->rxcall)) {
+				/* rxrpc terminated the call. */
+				rxrpc_complete = true;
+				break;
+			}
+
+			schedule();
+		}
+
+		remove_wait_queue(&call->waitq, &myself);
+		__set_current_state(TASK_RUNNING);
+	}
+
+	if (!afs_check_call_state(call, AFS_CALL_COMPLETE)) {
+		if (rxrpc_complete) {
+			afs_set_call_complete(call, call->error, call->abort_code);
+		} else {
+			/* Kill off the call if it's still live. */
+			_debug("call interrupted");
+			if (rxrpc_kernel_abort_call(call->net->socket, call->rxcall,
+						    RX_USER_ABORT, -EINTR,
+						    afs_abort_interrupted))
+				afs_set_call_complete(call, -EINTR, 0);
+		}
+	}
+}
+
+/*
+ * wake up a waiting call
+ */
+static void afs_wake_up_call_waiter(struct sock *sk, struct rxrpc_call *rxcall,
+				    unsigned long call_user_ID)
+{
+	struct afs_call *call = (struct afs_call *)call_user_ID;
+
+	call->need_attention = true;
+	wake_up(&call->waitq);
+}
+
+/*
+ * Wake up an asynchronous call.  The caller is holding the call notify
+ * spinlock around this, so we can't call afs_put_call().
+ */
+static void afs_wake_up_async_call(struct sock *sk, struct rxrpc_call *rxcall,
+				   unsigned long call_user_ID)
+{
+	struct afs_call *call = (struct afs_call *)call_user_ID;
+	int r;
+
+	trace_afs_notify_call(rxcall, call);
+	call->need_attention = true;
+
+	if (__refcount_inc_not_zero(&call->ref, &r)) {
+		trace_afs_call(call->debug_id, afs_call_trace_wake, r + 1,
+			       atomic_read(&call->net->nr_outstanding_calls),
+			       __builtin_return_address(0));
+
+		if (!queue_work(afs_async_calls, &call->async_work))
+			afs_deferred_put_call(call);
+	}
+}
+
+/*
+ * Perform I/O processing on an asynchronous call.  The work item carries a ref
+ * to the call struct that we either need to release or to pass on.
+ */
+static void afs_process_async_call(struct work_struct *work)
+{
+	struct afs_call *call = container_of(work, struct afs_call, async_work);
+
+	_enter("");
+
+	if (call->state < AFS_CALL_COMPLETE && call->need_attention) {
+		call->need_attention = false;
+		afs_deliver_to_call(call);
+	}
+
+	afs_put_call(call);
+	_leave("");
+}
+
+static void afs_rx_attach(struct rxrpc_call *rxcall, unsigned long user_call_ID)
+{
+	struct afs_call *call = (struct afs_call *)user_call_ID;
+
+	call->rxcall = rxcall;
+}
+
+/*
+ * Charge the incoming call preallocation.
+ */
+void afs_charge_preallocation(struct work_struct *work)
+{
+	struct afs_net *net =
+		container_of(work, struct afs_net, charge_preallocation_work);
+	struct afs_call *call = net->spare_incoming_call;
+
+	while (READ_ONCE(net->live)) {
+		if (!call) {
+			call = afs_alloc_call(net, &afs_RXCMxxxx, GFP_KERNEL);
+			if (!call)
+				break;
+
+			call->drop_ref = true;
+			call->async = true;
+			call->state = AFS_CALL_SV_AWAIT_OP_ID;
+			init_waitqueue_head(&call->waitq);
+			afs_extract_to_tmp(call);
+		}
+
+		if (rxrpc_kernel_charge_accept(net->socket,
+					       afs_wake_up_async_call,
+					       (unsigned long)call,
+					       GFP_KERNEL,
+					       call->debug_id) < 0)
+			break;
+		call = NULL;
+	}
+	net->spare_incoming_call = call;
+}
+
+/*
+ * Discard a preallocated call when a socket is shut down.
+ */
+static void afs_rx_discard_new_call(struct rxrpc_call *rxcall,
+				    unsigned long user_call_ID)
+{
+	struct afs_call *call = (struct afs_call *)user_call_ID;
+
+	call->rxcall = NULL;
+	afs_put_call(call);
+}
+
+/*
+ * Notification of an incoming call.
+ */
+static void afs_rx_new_call(struct sock *sk, struct rxrpc_call *rxcall,
+			    unsigned long user_call_ID)
+{
+	struct afs_call *call = (struct afs_call *)user_call_ID;
+	struct afs_net *net = afs_sock2net(sk);
+
+	call->peer = rxrpc_kernel_get_call_peer(sk->sk_socket, call->rxcall);
+	call->server = afs_find_server(call->peer);
+	if (!call->server)
+		trace_afs_cm_no_server(call, rxrpc_kernel_remote_srx(call->peer));
+
+	if (net->live)
+		queue_work(afs_wq, &net->charge_preallocation_work);
+}
+
+/*
+ * Grab the operation ID from an incoming cache manager call.  The socket
+ * buffer is discarded on error or if we don't yet have sufficient data.
+ */
+static int afs_deliver_cm_op_id(struct afs_call *call)
+{
+	int ret;
+
+	_enter("{%zu}", iov_iter_count(call->iter));
+
+	/* the operation ID forms the first four bytes of the request data */
+	ret = afs_extract_data(call, true);
+	if (ret < 0)
+		return ret;
+
+	call->operation_ID = ntohl(call->tmp);
+	afs_set_call_state(call, AFS_CALL_SV_AWAIT_OP_ID, AFS_CALL_SV_AWAIT_REQUEST);
+
+	/* ask the cache manager to route the call (it'll change the call type
+	 * if successful) */
+	if (!afs_cm_incoming_call(call))
+		return -ENOTSUPP;
+
+	call->security_ix = rxrpc_kernel_query_call_security(call->rxcall,
+							     &call->service_id,
+							     &call->enctype);
+
+	trace_afs_cb_call(call);
+	call->work.func = call->type->work;
+
+	/* pass responsibility for the remainder of this message off to the
+	 * cache manager op */
+	return call->type->deliver(call);
+}
+
+/*
+ * Advance the AFS call state when an RxRPC service call ends the transmit
+ * phase.
+ */
+static void afs_notify_end_reply_tx(struct sock *sock,
+				    struct rxrpc_call *rxcall,
+				    unsigned long call_user_ID)
+{
+	struct afs_call *call = (struct afs_call *)call_user_ID;
+
+	afs_set_call_state(call, AFS_CALL_SV_REPLYING, AFS_CALL_SV_AWAIT_ACK);
+}
+
+/*
+ * send an empty reply
+ */
+void afs_send_empty_reply(struct afs_call *call)
+{
+	struct afs_net *net = call->net;
+	struct msghdr msg;
+
+	_enter("");
+
+	rxrpc_kernel_set_tx_length(net->socket, call->rxcall, 0);
+
+	msg.msg_name		= NULL;
+	msg.msg_namelen		= 0;
+	iov_iter_kvec(&msg.msg_iter, ITER_SOURCE, NULL, 0, 0);
+	msg.msg_control		= NULL;
+	msg.msg_controllen	= 0;
+	msg.msg_flags		= 0;
+
+	switch (rxrpc_kernel_send_data(net->socket, call->rxcall, &msg, 0,
+				       afs_notify_end_reply_tx)) {
+	case 0:
+		_leave(" [replied]");
+		return;
+
+	case -ENOMEM:
+		_debug("oom");
+		rxrpc_kernel_abort_call(net->socket, call->rxcall,
+					RXGEN_SS_MARSHAL, -ENOMEM,
+					afs_abort_oom);
+		fallthrough;
+	default:
+		_leave(" [error]");
+		return;
+	}
+}
+
+/*
+ * send a simple reply
+ */
+void afs_send_simple_reply(struct afs_call *call, const void *buf, size_t len)
+{
+	struct afs_net *net = call->net;
+	struct msghdr msg;
+	struct kvec iov[1];
+	int n;
+
+	_enter("");
+
+	rxrpc_kernel_set_tx_length(net->socket, call->rxcall, len);
+
+	iov[0].iov_base		= (void *) buf;
+	iov[0].iov_len		= len;
+	msg.msg_name		= NULL;
+	msg.msg_namelen		= 0;
+	iov_iter_kvec(&msg.msg_iter, ITER_SOURCE, iov, 1, len);
+	msg.msg_control		= NULL;
+	msg.msg_controllen	= 0;
+	msg.msg_flags		= 0;
+
+	n = rxrpc_kernel_send_data(net->socket, call->rxcall, &msg, len,
+				   afs_notify_end_reply_tx);
+	if (n >= 0) {
+		/* Success */
+		_leave(" [replied]");
+		return;
+	}
+
+	if (n == -ENOMEM) {
+		_debug("oom");
+		rxrpc_kernel_abort_call(net->socket, call->rxcall,
+					RXGEN_SS_MARSHAL, -ENOMEM,
+					afs_abort_oom);
+	}
+	_leave(" [error]");
+}
+
+/*
+ * Extract a piece of data from the received data socket buffers.
+ */
+int afs_extract_data(struct afs_call *call, bool want_more)
+{
+	struct afs_net *net = call->net;
+	struct iov_iter *iter = call->iter;
+	enum afs_call_state state;
+	u32 remote_abort = 0;
+	int ret;
+
+	_enter("{%s,%zu,%zu},%d",
+	       call->type->name, call->iov_len, iov_iter_count(iter), want_more);
+
+	ret = rxrpc_kernel_recv_data(net->socket, call->rxcall, iter,
+				     &call->iov_len, want_more, &remote_abort,
+				     &call->service_id);
+	trace_afs_receive_data(call, call->iter, want_more, ret);
+	if (ret == 0 || ret == -EAGAIN)
+		return ret;
+
+	state = READ_ONCE(call->state);
+	if (ret == 1) {
+		switch (state) {
+		case AFS_CALL_CL_AWAIT_REPLY:
+			afs_set_call_state(call, state, AFS_CALL_CL_PROC_REPLY);
+			break;
+		case AFS_CALL_SV_AWAIT_REQUEST:
+			afs_set_call_state(call, state, AFS_CALL_SV_REPLYING);
+			break;
+		case AFS_CALL_COMPLETE:
+			kdebug("prem complete %d", call->error);
+			return afs_io_error(call, afs_io_error_extract);
+		default:
+			break;
+		}
+		return 0;
+	}
+
+	afs_set_call_complete(call, ret, remote_abort);
+	return ret;
+}
+
+/*
+ * Log protocol error production.
+ */
+noinline int afs_protocol_error(struct afs_call *call,
+				enum afs_eproto_cause cause)
+{
+	trace_afs_protocol_error(call, cause);
+	if (call)
+		call->unmarshalling_error = true;
+	return -EBADMSG;
+}
+
+/*
+ * Wake up OOB notification processing.
+ */
+static void afs_rx_notify_oob(struct sock *sk, struct sk_buff *oob)
+{
+	struct afs_net *net = sk->sk_user_data;
+
+	if (READ_ONCE(net->live))
+		queue_work(afs_wq, &net->rx_oob_work);
+}