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, 495 insertions, 0 deletions

diff --git a/net/rxrpc/conn_object.c b/net/rxrpc/conn_object.c
new file mode 100644
index 000000000..0ece717db
--- /dev/null
+++ b/net/rxrpc/conn_object.c
@@ -0,0 +1,495 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/* RxRPC virtual connection handler, common bits.
+ *
+ * Copyright (C) 2007, 2016 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/net.h>
+#include <linux/skbuff.h>
+#include "ar-internal.h"
+
+/*
+ * Time till a connection expires after last use (in seconds).
+ */
+unsigned int __read_mostly rxrpc_connection_expiry = 10 * 60;
+unsigned int __read_mostly rxrpc_closed_conn_expiry = 10;
+
+static void rxrpc_clean_up_connection(struct work_struct *work);
+static void rxrpc_set_service_reap_timer(struct rxrpc_net *rxnet,
+					 unsigned long reap_at);
+
+void rxrpc_poke_conn(struct rxrpc_connection *conn, enum rxrpc_conn_trace why)
+{
+	struct rxrpc_local *local = conn->local;
+	bool busy;
+
+	if (WARN_ON_ONCE(!local))
+		return;
+
+	spin_lock_irq(&local->lock);
+	busy = !list_empty(&conn->attend_link);
+	if (!busy) {
+		rxrpc_get_connection(conn, why);
+		list_add_tail(&conn->attend_link, &local->conn_attend_q);
+	}
+	spin_unlock_irq(&local->lock);
+	rxrpc_wake_up_io_thread(local);
+}
+
+static void rxrpc_connection_timer(struct timer_list *timer)
+{
+	struct rxrpc_connection *conn =
+		container_of(timer, struct rxrpc_connection, timer);
+
+	rxrpc_poke_conn(conn, rxrpc_conn_get_poke_timer);
+}
+
+/*
+ * allocate a new connection
+ */
+struct rxrpc_connection *rxrpc_alloc_connection(struct rxrpc_net *rxnet,
+						gfp_t gfp)
+{
+	struct rxrpc_connection *conn;
+
+	_enter("");
+
+	conn = kzalloc_obj(struct rxrpc_connection, gfp);
+	if (conn) {
+		INIT_LIST_HEAD(&conn->cache_link);
+		timer_setup(&conn->timer, &rxrpc_connection_timer, 0);
+		INIT_WORK(&conn->processor, rxrpc_process_connection);
+		INIT_WORK(&conn->destructor, rxrpc_clean_up_connection);
+		INIT_LIST_HEAD(&conn->proc_link);
+		INIT_LIST_HEAD(&conn->link);
+		INIT_LIST_HEAD(&conn->attend_link);
+		mutex_init(&conn->security_lock);
+		mutex_init(&conn->tx_data_alloc_lock);
+		skb_queue_head_init(&conn->rx_queue);
+		conn->rxnet = rxnet;
+		conn->security = &rxrpc_no_security;
+		rwlock_init(&conn->security_use_lock);
+		spin_lock_init(&conn->state_lock);
+		conn->debug_id = atomic_inc_return(&rxrpc_debug_id);
+		conn->idle_timestamp = jiffies;
+	}
+
+	_leave(" = %p{%d}", conn, conn ? conn->debug_id : 0);
+	return conn;
+}
+
+/*
+ * Look up a connection in the cache by protocol parameters.
+ *
+ * If successful, a pointer to the connection is returned, but no ref is taken.
+ * NULL is returned if there is no match.
+ *
+ * When searching for a service call, if we find a peer but no connection, we
+ * return that through *_peer in case we need to create a new service call.
+ *
+ * The caller must be holding the RCU read lock.
+ */
+struct rxrpc_connection *rxrpc_find_client_connection_rcu(struct rxrpc_local *local,
+							  struct sockaddr_rxrpc *srx,
+							  struct sk_buff *skb)
+{
+	struct rxrpc_connection *conn;
+	struct rxrpc_skb_priv *sp = rxrpc_skb(skb);
+	struct rxrpc_peer *peer;
+
+	_enter(",%x", sp->hdr.cid & RXRPC_CIDMASK);
+
+	/* Look up client connections by connection ID alone as their
+	 * IDs are unique for this machine.
+	 */
+	conn = idr_find(&local->conn_ids, sp->hdr.cid >> RXRPC_CIDSHIFT);
+	if (!conn || refcount_read(&conn->ref) == 0) {
+		_debug("no conn");
+		goto not_found;
+	}
+
+	if (conn->proto.epoch != sp->hdr.epoch ||
+	    conn->local != local)
+		goto not_found;
+
+	peer = conn->peer;
+	switch (srx->transport.family) {
+	case AF_INET:
+		if (peer->srx.transport.sin.sin_port !=
+		    srx->transport.sin.sin_port)
+			goto not_found;
+		break;
+#ifdef CONFIG_AF_RXRPC_IPV6
+	case AF_INET6:
+		if (peer->srx.transport.sin6.sin6_port !=
+		    srx->transport.sin6.sin6_port)
+			goto not_found;
+		break;
+#endif
+	default:
+		BUG();
+	}
+
+	_leave(" = %p", conn);
+	return conn;
+
+not_found:
+	_leave(" = NULL");
+	return NULL;
+}
+
+/*
+ * Disconnect a call and clear any channel it occupies when that call
+ * terminates.  The caller must hold the channel_lock and must release the
+ * call's ref on the connection.
+ */
+void __rxrpc_disconnect_call(struct rxrpc_connection *conn,
+			     struct rxrpc_call *call)
+{
+	struct rxrpc_channel *chan =
+		&conn->channels[call->cid & RXRPC_CHANNELMASK];
+
+	_enter("%d,%x", conn->debug_id, call->cid);
+
+	if (chan->call == call) {
+		/* Save the result of the call so that we can repeat it if necessary
+		 * through the channel, whilst disposing of the actual call record.
+		 */
+		trace_rxrpc_disconnect_call(call);
+		switch (call->completion) {
+		case RXRPC_CALL_SUCCEEDED:
+			chan->last_seq = call->rx_highest_seq;
+			chan->last_type = RXRPC_PACKET_TYPE_ACK;
+			break;
+		case RXRPC_CALL_LOCALLY_ABORTED:
+			chan->last_abort = call->abort_code;
+			chan->last_type = RXRPC_PACKET_TYPE_ABORT;
+			break;
+		default:
+			chan->last_abort = RX_CALL_DEAD;
+			chan->last_type = RXRPC_PACKET_TYPE_ABORT;
+			break;
+		}
+
+		chan->last_call = chan->call_id;
+		chan->call_id = chan->call_counter;
+		chan->call = NULL;
+	}
+
+	_leave("");
+}
+
+/*
+ * Disconnect a call and clear any channel it occupies when that call
+ * terminates.
+ */
+void rxrpc_disconnect_call(struct rxrpc_call *call)
+{
+	struct rxrpc_connection *conn = call->conn;
+
+	set_bit(RXRPC_CALL_DISCONNECTED, &call->flags);
+	rxrpc_see_call(call, rxrpc_call_see_disconnected);
+
+	call->peer->cong_ssthresh = call->cong_ssthresh;
+
+	if (!hlist_unhashed(&call->error_link)) {
+		spin_lock_irq(&call->peer->lock);
+		hlist_del_init(&call->error_link);
+		spin_unlock_irq(&call->peer->lock);
+	}
+
+	if (rxrpc_is_client_call(call)) {
+		rxrpc_disconnect_client_call(call->bundle, call);
+	} else {
+		__rxrpc_disconnect_call(conn, call);
+		conn->idle_timestamp = jiffies;
+		if (atomic_dec_and_test(&conn->active))
+			rxrpc_set_service_reap_timer(conn->rxnet,
+						     jiffies + rxrpc_connection_expiry * HZ);
+	}
+
+	rxrpc_put_call(call, rxrpc_call_put_io_thread);
+}
+
+/*
+ * Queue a connection's work processor, getting a ref to pass to the work
+ * queue.
+ */
+void rxrpc_queue_conn(struct rxrpc_connection *conn, enum rxrpc_conn_trace why)
+{
+	if (atomic_read(&conn->active) >= 0 &&
+	    rxrpc_queue_work(&conn->processor))
+		rxrpc_see_connection(conn, why);
+}
+
+/*
+ * Note the re-emergence of a connection.
+ */
+void rxrpc_see_connection(struct rxrpc_connection *conn,
+			  enum rxrpc_conn_trace why)
+{
+	if (conn) {
+		int r = refcount_read(&conn->ref);
+
+		trace_rxrpc_conn(conn->debug_id, r, why);
+	}
+}
+
+/*
+ * Get a ref on a connection.
+ */
+struct rxrpc_connection *rxrpc_get_connection(struct rxrpc_connection *conn,
+					      enum rxrpc_conn_trace why)
+{
+	int r;
+
+	__refcount_inc(&conn->ref, &r);
+	trace_rxrpc_conn(conn->debug_id, r + 1, why);
+	return conn;
+}
+
+/*
+ * Try to get a ref on a connection.
+ */
+struct rxrpc_connection *
+rxrpc_get_connection_maybe(struct rxrpc_connection *conn,
+			   enum rxrpc_conn_trace why)
+{
+	int r;
+
+	if (conn) {
+		if (__refcount_inc_not_zero(&conn->ref, &r))
+			trace_rxrpc_conn(conn->debug_id, r + 1, why);
+		else
+			conn = NULL;
+	}
+	return conn;
+}
+
+/*
+ * Set the service connection reap timer.
+ */
+static void rxrpc_set_service_reap_timer(struct rxrpc_net *rxnet,
+					 unsigned long reap_at)
+{
+	if (rxnet->live)
+		timer_reduce(&rxnet->service_conn_reap_timer, reap_at);
+}
+
+/*
+ * destroy a virtual connection
+ */
+static void rxrpc_rcu_free_connection(struct rcu_head *rcu)
+{
+	struct rxrpc_connection *conn =
+		container_of(rcu, struct rxrpc_connection, rcu);
+	struct rxrpc_net *rxnet = conn->rxnet;
+
+	_enter("{%d,u=%d}", conn->debug_id, refcount_read(&conn->ref));
+
+	trace_rxrpc_conn(conn->debug_id, refcount_read(&conn->ref),
+			 rxrpc_conn_free);
+	kfree(conn);
+
+	if (atomic_dec_and_test(&rxnet->nr_conns))
+		wake_up_var(&rxnet->nr_conns);
+}
+
+/*
+ * Clean up a dead connection.
+ */
+static void rxrpc_clean_up_connection(struct work_struct *work)
+{
+	struct rxrpc_connection *conn =
+		container_of(work, struct rxrpc_connection, destructor);
+	struct rxrpc_net *rxnet = conn->rxnet;
+
+	ASSERT(!conn->channels[0].call &&
+	       !conn->channels[1].call &&
+	       !conn->channels[2].call &&
+	       !conn->channels[3].call);
+	ASSERT(list_empty(&conn->cache_link));
+
+	timer_delete_sync(&conn->timer);
+	cancel_work_sync(&conn->processor); /* Processing may restart the timer */
+	timer_delete_sync(&conn->timer);
+
+	write_lock(&rxnet->conn_lock);
+	list_del_init(&conn->proc_link);
+	write_unlock(&rxnet->conn_lock);
+
+	if (conn->pmtud_probe) {
+		trace_rxrpc_pmtud_lost(conn, 0);
+		conn->peer->pmtud_probing = false;
+		conn->peer->pmtud_pending = true;
+	}
+
+	rxrpc_purge_queue(&conn->rx_queue);
+	rxrpc_free_skb(conn->tx_response, rxrpc_skb_put_response);
+
+	rxrpc_kill_client_conn(conn);
+
+	conn->security->clear(conn);
+	key_put(conn->key);
+	rxrpc_put_bundle(conn->bundle, rxrpc_bundle_put_conn);
+	rxrpc_put_peer(conn->peer, rxrpc_peer_put_conn);
+	rxrpc_put_local(conn->local, rxrpc_local_put_kill_conn);
+
+	/* Drain the Rx queue.  Note that even though we've unpublished, an
+	 * incoming packet could still be being added to our Rx queue, so we
+	 * will need to drain it again in the RCU cleanup handler.
+	 */
+	rxrpc_purge_queue(&conn->rx_queue);
+
+	page_frag_cache_drain(&conn->tx_data_alloc);
+	call_rcu(&conn->rcu, rxrpc_rcu_free_connection);
+}
+
+/*
+ * Drop a ref on a connection.
+ */
+void rxrpc_put_connection(struct rxrpc_connection *conn,
+			  enum rxrpc_conn_trace why)
+{
+	unsigned int debug_id;
+	bool dead;
+	int r;
+
+	if (!conn)
+		return;
+
+	debug_id = conn->debug_id;
+	dead = __refcount_dec_and_test(&conn->ref, &r);
+	trace_rxrpc_conn(debug_id, r - 1, why);
+	if (dead) {
+		timer_delete(&conn->timer);
+		cancel_work(&conn->processor);
+
+		if (in_softirq() || work_busy(&conn->processor) ||
+		    timer_pending(&conn->timer))
+			/* Can't use the rxrpc workqueue as we need to cancel/flush
+			 * something that may be running/waiting there.
+			 */
+			schedule_work(&conn->destructor);
+		else
+			rxrpc_clean_up_connection(&conn->destructor);
+	}
+}
+
+/*
+ * reap dead service connections
+ */
+void rxrpc_service_connection_reaper(struct work_struct *work)
+{
+	struct rxrpc_connection *conn, *_p;
+	struct rxrpc_net *rxnet =
+		container_of(work, struct rxrpc_net, service_conn_reaper);
+	unsigned long expire_at, earliest, idle_timestamp, now;
+	int active;
+
+	LIST_HEAD(graveyard);
+
+	_enter("");
+
+	now = jiffies;
+	earliest = now + MAX_JIFFY_OFFSET;
+
+	write_lock(&rxnet->conn_lock);
+	list_for_each_entry_safe(conn, _p, &rxnet->service_conns, link) {
+		ASSERTCMP(atomic_read(&conn->active), >=, 0);
+		if (likely(atomic_read(&conn->active) > 0))
+			continue;
+		if (conn->state == RXRPC_CONN_SERVICE_PREALLOC)
+			continue;
+
+		if (rxnet->live && !conn->local->dead) {
+			idle_timestamp = READ_ONCE(conn->idle_timestamp);
+			expire_at = idle_timestamp + rxrpc_connection_expiry * HZ;
+			if (conn->local->service_closed)
+				expire_at = idle_timestamp + rxrpc_closed_conn_expiry * HZ;
+
+			_debug("reap CONN %d { a=%d,t=%ld }",
+			       conn->debug_id, atomic_read(&conn->active),
+			       (long)expire_at - (long)now);
+
+			if (time_before(now, expire_at)) {
+				if (time_before(expire_at, earliest))
+					earliest = expire_at;
+				continue;
+			}
+		}
+
+		/* The activity count sits at 0 whilst the conn is unused on
+		 * the list; we reduce that to -1 to make the conn unavailable.
+		 */
+		active = 0;
+		if (!atomic_try_cmpxchg(&conn->active, &active, -1))
+			continue;
+		rxrpc_see_connection(conn, rxrpc_conn_see_reap_service);
+
+		if (rxrpc_conn_is_client(conn))
+			BUG();
+		else
+			rxrpc_unpublish_service_conn(conn);
+
+		list_move_tail(&conn->link, &graveyard);
+	}
+	write_unlock(&rxnet->conn_lock);
+
+	if (earliest != now + MAX_JIFFY_OFFSET) {
+		_debug("reschedule reaper %ld", (long)earliest - (long)now);
+		ASSERT(time_after(earliest, now));
+		rxrpc_set_service_reap_timer(rxnet, earliest);
+	}
+
+	while (!list_empty(&graveyard)) {
+		conn = list_entry(graveyard.next, struct rxrpc_connection,
+				  link);
+		list_del_init(&conn->link);
+
+		ASSERTCMP(atomic_read(&conn->active), ==, -1);
+		rxrpc_put_connection(conn, rxrpc_conn_put_service_reaped);
+	}
+
+	_leave("");
+}
+
+/*
+ * preemptively destroy all the service connection records rather than
+ * waiting for them to time out
+ */
+void rxrpc_destroy_all_connections(struct rxrpc_net *rxnet)
+{
+	struct rxrpc_connection *conn, *_p;
+	bool leak = false;
+
+	_enter("");
+
+	atomic_dec(&rxnet->nr_conns);
+
+	timer_delete_sync(&rxnet->service_conn_reap_timer);
+	rxrpc_queue_work(&rxnet->service_conn_reaper);
+	flush_workqueue(rxrpc_workqueue);
+
+	write_lock(&rxnet->conn_lock);
+	list_for_each_entry_safe(conn, _p, &rxnet->service_conns, link) {
+		pr_err("AF_RXRPC: Leaked conn %p {%d}\n",
+		       conn, refcount_read(&conn->ref));
+		leak = true;
+	}
+	write_unlock(&rxnet->conn_lock);
+	BUG_ON(leak);
+
+	ASSERT(list_empty(&rxnet->conn_proc_list));
+
+	/* We need to wait for the connections to be destroyed by RCU as they
+	 * pin things that we still need to get rid of.
+	 */
+	wait_var_event(&rxnet->nr_conns, !atomic_read(&rxnet->nr_conns));
+	_leave("");
+}