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, 234 insertions, 0 deletions

diff --git a/drivers/bluetooth/btqcomsmd.c b/drivers/bluetooth/btqcomsmd.c
new file mode 100644
index 000000000..d669ea4eb
--- /dev/null
+++ b/drivers/bluetooth/btqcomsmd.c
@@ -0,0 +1,234 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (c) 2016, Linaro Ltd.
+ * Copyright (c) 2015, Sony Mobile Communications Inc.
+ */
+
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/rpmsg.h>
+#include <linux/of.h>
+
+#include <linux/soc/qcom/wcnss_ctrl.h>
+#include <linux/platform_device.h>
+
+#include <net/bluetooth/bluetooth.h>
+#include <net/bluetooth/hci_core.h>
+
+#include "btqca.h"
+
+struct btqcomsmd {
+	struct hci_dev *hdev;
+
+	struct rpmsg_endpoint *acl_channel;
+	struct rpmsg_endpoint *cmd_channel;
+};
+
+static int btqcomsmd_recv(struct hci_dev *hdev, unsigned int type,
+			   const void *data, size_t count)
+{
+	struct sk_buff *skb;
+
+	/* Use GFP_ATOMIC as we're in IRQ context */
+	skb = bt_skb_alloc(count, GFP_ATOMIC);
+	if (!skb) {
+		hdev->stat.err_rx++;
+		return -ENOMEM;
+	}
+
+	hci_skb_pkt_type(skb) = type;
+	skb_put_data(skb, data, count);
+
+	return hci_recv_frame(hdev, skb);
+}
+
+static int btqcomsmd_acl_callback(struct rpmsg_device *rpdev, void *data,
+				  int count, void *priv, u32 addr)
+{
+	struct btqcomsmd *btq = priv;
+
+	btq->hdev->stat.byte_rx += count;
+	return btqcomsmd_recv(btq->hdev, HCI_ACLDATA_PKT, data, count);
+}
+
+static int btqcomsmd_cmd_callback(struct rpmsg_device *rpdev, void *data,
+				  int count, void *priv, u32 addr)
+{
+	struct btqcomsmd *btq = priv;
+
+	btq->hdev->stat.byte_rx += count;
+	return btqcomsmd_recv(btq->hdev, HCI_EVENT_PKT, data, count);
+}
+
+static int btqcomsmd_send(struct hci_dev *hdev, struct sk_buff *skb)
+{
+	struct btqcomsmd *btq = hci_get_drvdata(hdev);
+	int ret;
+
+	switch (hci_skb_pkt_type(skb)) {
+	case HCI_ACLDATA_PKT:
+		ret = rpmsg_send(btq->acl_channel, skb->data, skb->len);
+		if (ret) {
+			hdev->stat.err_tx++;
+			break;
+		}
+		hdev->stat.acl_tx++;
+		hdev->stat.byte_tx += skb->len;
+		break;
+	case HCI_COMMAND_PKT:
+		ret = rpmsg_send(btq->cmd_channel, skb->data, skb->len);
+		if (ret) {
+			hdev->stat.err_tx++;
+			break;
+		}
+		hdev->stat.cmd_tx++;
+		hdev->stat.byte_tx += skb->len;
+		break;
+	default:
+		ret = -EILSEQ;
+		break;
+	}
+
+	if (!ret)
+		kfree_skb(skb);
+
+	return ret;
+}
+
+static int btqcomsmd_open(struct hci_dev *hdev)
+{
+	return 0;
+}
+
+static int btqcomsmd_close(struct hci_dev *hdev)
+{
+	return 0;
+}
+
+static int btqcomsmd_setup(struct hci_dev *hdev)
+{
+	struct sk_buff *skb;
+
+	skb = __hci_cmd_sync(hdev, HCI_OP_RESET, 0, NULL, HCI_INIT_TIMEOUT);
+	if (IS_ERR(skb))
+		return PTR_ERR(skb);
+	kfree_skb(skb);
+
+	/* Devices do not have persistent storage for BD address. Retrieve
+	 * it from the firmware node property.
+	 */
+	hci_set_quirk(hdev, HCI_QUIRK_USE_BDADDR_PROPERTY);
+
+	return 0;
+}
+
+static int btqcomsmd_set_bdaddr(struct hci_dev *hdev, const bdaddr_t *bdaddr)
+{
+	int ret;
+
+	ret = qca_set_bdaddr_rome(hdev, bdaddr);
+	if (ret)
+		return ret;
+
+	/* The firmware stops responding for a while after setting the bdaddr,
+	 * causing timeouts for subsequent commands. Sleep a bit to avoid this.
+	 */
+	usleep_range(1000, 10000);
+	return 0;
+}
+
+static int btqcomsmd_probe(struct platform_device *pdev)
+{
+	struct btqcomsmd *btq;
+	struct hci_dev *hdev;
+	void *wcnss;
+	int ret;
+
+	btq = devm_kzalloc(&pdev->dev, sizeof(*btq), GFP_KERNEL);
+	if (!btq)
+		return -ENOMEM;
+
+	wcnss = dev_get_drvdata(pdev->dev.parent);
+
+	btq->acl_channel = qcom_wcnss_open_channel(wcnss, "APPS_RIVA_BT_ACL",
+						   btqcomsmd_acl_callback, btq);
+	if (IS_ERR(btq->acl_channel))
+		return PTR_ERR(btq->acl_channel);
+
+	btq->cmd_channel = qcom_wcnss_open_channel(wcnss, "APPS_RIVA_BT_CMD",
+						   btqcomsmd_cmd_callback, btq);
+	if (IS_ERR(btq->cmd_channel)) {
+		ret = PTR_ERR(btq->cmd_channel);
+		goto destroy_acl_channel;
+	}
+
+	hdev = hci_alloc_dev();
+	if (!hdev) {
+		ret = -ENOMEM;
+		goto destroy_cmd_channel;
+	}
+
+	hci_set_drvdata(hdev, btq);
+	btq->hdev = hdev;
+	SET_HCIDEV_DEV(hdev, &pdev->dev);
+
+	hdev->bus = HCI_SMD;
+	hdev->open = btqcomsmd_open;
+	hdev->close = btqcomsmd_close;
+	hdev->send = btqcomsmd_send;
+	hdev->setup = btqcomsmd_setup;
+	hdev->set_bdaddr = btqcomsmd_set_bdaddr;
+
+	ret = hci_register_dev(hdev);
+	if (ret < 0)
+		goto hci_free_dev;
+
+	platform_set_drvdata(pdev, btq);
+
+	return 0;
+
+hci_free_dev:
+	rpmsg_destroy_ept(btq->cmd_channel);
+	rpmsg_destroy_ept(btq->acl_channel);
+	hci_free_dev(hdev);
+	return ret;
+destroy_cmd_channel:
+	rpmsg_destroy_ept(btq->cmd_channel);
+destroy_acl_channel:
+	rpmsg_destroy_ept(btq->acl_channel);
+
+	return ret;
+}
+
+static void btqcomsmd_remove(struct platform_device *pdev)
+{
+	struct btqcomsmd *btq = platform_get_drvdata(pdev);
+
+	hci_unregister_dev(btq->hdev);
+
+	rpmsg_destroy_ept(btq->cmd_channel);
+	rpmsg_destroy_ept(btq->acl_channel);
+
+	hci_free_dev(btq->hdev);
+}
+
+static const struct of_device_id btqcomsmd_of_match[] = {
+	{ .compatible = "qcom,wcnss-bt", },
+	{ },
+};
+MODULE_DEVICE_TABLE(of, btqcomsmd_of_match);
+
+static struct platform_driver btqcomsmd_driver = {
+	.probe = btqcomsmd_probe,
+	.remove = btqcomsmd_remove,
+	.driver  = {
+		.name  = "btqcomsmd",
+		.of_match_table = btqcomsmd_of_match,
+	},
+};
+
+module_platform_driver(btqcomsmd_driver);
+
+MODULE_AUTHOR("Bjorn Andersson <bjorn.andersson@sonymobile.com>");
+MODULE_DESCRIPTION("Qualcomm SMD HCI driver");
+MODULE_LICENSE("GPL v2");