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, 240 insertions, 0 deletions

diff --git a/net/mac802154/tx.c b/net/mac802154/tx.c
new file mode 100644
index 000000000..4d13f18f6
--- /dev/null
+++ b/net/mac802154/tx.c
@@ -0,0 +1,240 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright 2007-2012 Siemens AG
+ *
+ * Written by:
+ * Dmitry Eremin-Solenikov <dbaryshkov@gmail.com>
+ * Sergey Lapin <slapin@ossfans.org>
+ * Maxim Gorbachyov <maxim.gorbachev@siemens.com>
+ * Alexander Smirnov <alex.bluesman.smirnov@gmail.com>
+ */
+
+#include <linux/netdevice.h>
+#include <linux/if_arp.h>
+#include <linux/crc-ccitt.h>
+#include <linux/unaligned.h>
+
+#include <net/rtnetlink.h>
+#include <net/ieee802154_netdev.h>
+#include <net/mac802154.h>
+#include <net/cfg802154.h>
+
+#include "ieee802154_i.h"
+#include "driver-ops.h"
+
+void ieee802154_xmit_sync_worker(struct work_struct *work)
+{
+	struct ieee802154_local *local =
+		container_of(work, struct ieee802154_local, sync_tx_work);
+	struct sk_buff *skb = local->tx_skb;
+	struct net_device *dev = skb->dev;
+	int res;
+
+	res = drv_xmit_sync(local, skb);
+	if (res)
+		goto err_tx;
+
+	DEV_STATS_INC(dev, tx_packets);
+	DEV_STATS_ADD(dev, tx_bytes, skb->len);
+
+	ieee802154_xmit_complete(&local->hw, skb, false);
+
+	return;
+
+err_tx:
+	/* Restart the netif queue on each sub_if_data object. */
+	ieee802154_release_queue(local);
+	if (atomic_dec_and_test(&local->phy->ongoing_txs))
+		wake_up(&local->phy->sync_txq);
+	kfree_skb(skb);
+	netdev_dbg(dev, "transmission failed\n");
+}
+
+static netdev_tx_t
+ieee802154_tx(struct ieee802154_local *local, struct sk_buff *skb)
+{
+	struct net_device *dev = skb->dev;
+	int ret;
+
+	if (!(local->hw.flags & IEEE802154_HW_TX_OMIT_CKSUM)) {
+		struct sk_buff *nskb;
+		u16 crc;
+
+		if (unlikely(skb_tailroom(skb) < IEEE802154_FCS_LEN)) {
+			nskb = skb_copy_expand(skb, 0, IEEE802154_FCS_LEN,
+					       GFP_ATOMIC);
+			if (likely(nskb)) {
+				consume_skb(skb);
+				skb = nskb;
+			} else {
+				goto err_free_skb;
+			}
+		}
+
+		crc = crc_ccitt(0, skb->data, skb->len);
+		put_unaligned_le16(crc, skb_put(skb, 2));
+	}
+
+	/* Stop the netif queue on each sub_if_data object. */
+	ieee802154_hold_queue(local);
+	atomic_inc(&local->phy->ongoing_txs);
+
+	/* Drivers should preferably implement the async callback. In some rare
+	 * cases they only provide a sync callback which we will use as a
+	 * fallback.
+	 */
+	if (local->ops->xmit_async) {
+		unsigned int len = skb->len;
+
+		ret = drv_xmit_async(local, skb);
+		if (ret)
+			goto err_wake_netif_queue;
+
+		DEV_STATS_INC(dev, tx_packets);
+		DEV_STATS_ADD(dev, tx_bytes, len);
+	} else {
+		local->tx_skb = skb;
+		queue_work(local->workqueue, &local->sync_tx_work);
+	}
+
+	return NETDEV_TX_OK;
+
+err_wake_netif_queue:
+	ieee802154_release_queue(local);
+	if (atomic_dec_and_test(&local->phy->ongoing_txs))
+		wake_up(&local->phy->sync_txq);
+err_free_skb:
+	kfree_skb(skb);
+	return NETDEV_TX_OK;
+}
+
+static int ieee802154_sync_queue(struct ieee802154_local *local)
+{
+	int ret;
+
+	ieee802154_hold_queue(local);
+	ieee802154_disable_queue(local);
+	wait_event(local->phy->sync_txq, !atomic_read(&local->phy->ongoing_txs));
+	ret = local->tx_result;
+	ieee802154_release_queue(local);
+
+	return ret;
+}
+
+int ieee802154_sync_and_hold_queue(struct ieee802154_local *local)
+{
+	int ret;
+
+	ieee802154_hold_queue(local);
+	ret = ieee802154_sync_queue(local);
+	set_bit(WPAN_PHY_FLAG_STATE_QUEUE_STOPPED, &local->phy->flags);
+
+	return ret;
+}
+
+int ieee802154_mlme_op_pre(struct ieee802154_local *local)
+{
+	return ieee802154_sync_and_hold_queue(local);
+}
+
+int ieee802154_mlme_tx_locked(struct ieee802154_local *local,
+			      struct ieee802154_sub_if_data *sdata,
+			      struct sk_buff *skb)
+{
+	/* Avoid possible calls to ->ndo_stop() when we asynchronously perform
+	 * MLME transmissions.
+	 */
+	ASSERT_RTNL();
+
+	/* Ensure the device was not stopped, otherwise error out */
+	if (!local->open_count)
+		return -ENETDOWN;
+
+	/* Warn if the ieee802154 core thinks MLME frames can be sent while the
+	 * net interface expects this cannot happen.
+	 */
+	if (WARN_ON_ONCE(!netif_running(sdata->dev)))
+		return -ENETDOWN;
+
+	ieee802154_tx(local, skb);
+	return ieee802154_sync_queue(local);
+}
+
+int ieee802154_mlme_tx(struct ieee802154_local *local,
+		       struct ieee802154_sub_if_data *sdata,
+		       struct sk_buff *skb)
+{
+	int ret;
+
+	rtnl_lock();
+	ret = ieee802154_mlme_tx_locked(local, sdata, skb);
+	rtnl_unlock();
+
+	return ret;
+}
+
+void ieee802154_mlme_op_post(struct ieee802154_local *local)
+{
+	ieee802154_release_queue(local);
+}
+
+int ieee802154_mlme_tx_one_locked(struct ieee802154_local *local,
+				  struct ieee802154_sub_if_data *sdata,
+				  struct sk_buff *skb)
+{
+	int ret;
+
+	ieee802154_mlme_op_pre(local);
+	ret = ieee802154_mlme_tx_locked(local, sdata, skb);
+	ieee802154_mlme_op_post(local);
+
+	return ret;
+}
+
+static bool ieee802154_queue_is_stopped(struct ieee802154_local *local)
+{
+	return test_bit(WPAN_PHY_FLAG_STATE_QUEUE_STOPPED, &local->phy->flags);
+}
+
+static netdev_tx_t
+ieee802154_hot_tx(struct ieee802154_local *local, struct sk_buff *skb)
+{
+	/* Warn if the net interface tries to transmit frames while the
+	 * ieee802154 core assumes the queue is stopped.
+	 */
+	WARN_ON_ONCE(ieee802154_queue_is_stopped(local));
+
+	return ieee802154_tx(local, skb);
+}
+
+netdev_tx_t
+ieee802154_monitor_start_xmit(struct sk_buff *skb, struct net_device *dev)
+{
+	struct ieee802154_sub_if_data *sdata = IEEE802154_DEV_TO_SUB_IF(dev);
+
+	skb->skb_iif = dev->ifindex;
+
+	return ieee802154_hot_tx(sdata->local, skb);
+}
+
+netdev_tx_t
+ieee802154_subif_start_xmit(struct sk_buff *skb, struct net_device *dev)
+{
+	struct ieee802154_sub_if_data *sdata = IEEE802154_DEV_TO_SUB_IF(dev);
+	int rc;
+
+	/* TODO we should move it to wpan_dev_hard_header and dev_hard_header
+	 * functions. The reason is wireshark will show a mac header which is
+	 * with security fields but the payload is not encrypted.
+	 */
+	rc = mac802154_llsec_encrypt(&sdata->sec, skb);
+	if (rc) {
+		netdev_warn(dev, "encryption failed: %i\n", rc);
+		kfree_skb(skb);
+		return NETDEV_TX_OK;
+	}
+
+	skb->skb_iif = dev->ifindex;
+
+	return ieee802154_hot_tx(sdata->local, skb);
+}