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, 235 insertions, 0 deletions

diff --git a/drivers/greybus/module.c b/drivers/greybus/module.c
new file mode 100644
index 000000000..709da8ef5
--- /dev/null
+++ b/drivers/greybus/module.c
@@ -0,0 +1,235 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Greybus Module code
+ *
+ * Copyright 2016 Google Inc.
+ * Copyright 2016 Linaro Ltd.
+ */
+
+#include <linux/greybus.h>
+#include "greybus_trace.h"
+
+static ssize_t eject_store(struct device *dev,
+			   struct device_attribute *attr,
+			   const char *buf, size_t len)
+{
+	struct gb_module *module = to_gb_module(dev);
+	struct gb_interface *intf;
+	size_t i;
+	long val;
+	int ret;
+
+	ret = kstrtol(buf, 0, &val);
+	if (ret)
+		return ret;
+
+	if (!val)
+		return len;
+
+	for (i = 0; i < module->num_interfaces; ++i) {
+		intf = module->interfaces[i];
+
+		mutex_lock(&intf->mutex);
+		/* Set flag to prevent concurrent activation. */
+		intf->ejected = true;
+		gb_interface_disable(intf);
+		gb_interface_deactivate(intf);
+		mutex_unlock(&intf->mutex);
+	}
+
+	/* Tell the SVC to eject the primary interface. */
+	ret = gb_svc_intf_eject(module->hd->svc, module->module_id);
+	if (ret)
+		return ret;
+
+	return len;
+}
+static DEVICE_ATTR_WO(eject);
+
+static ssize_t module_id_show(struct device *dev,
+			      struct device_attribute *attr, char *buf)
+{
+	struct gb_module *module = to_gb_module(dev);
+
+	return sprintf(buf, "%u\n", module->module_id);
+}
+static DEVICE_ATTR_RO(module_id);
+
+static ssize_t num_interfaces_show(struct device *dev,
+				   struct device_attribute *attr, char *buf)
+{
+	struct gb_module *module = to_gb_module(dev);
+
+	return sprintf(buf, "%zu\n", module->num_interfaces);
+}
+static DEVICE_ATTR_RO(num_interfaces);
+
+static struct attribute *module_attrs[] = {
+	&dev_attr_eject.attr,
+	&dev_attr_module_id.attr,
+	&dev_attr_num_interfaces.attr,
+	NULL,
+};
+ATTRIBUTE_GROUPS(module);
+
+static void gb_module_release(struct device *dev)
+{
+	struct gb_module *module = to_gb_module(dev);
+
+	trace_gb_module_release(module);
+
+	kfree(module);
+}
+
+const struct device_type greybus_module_type = {
+	.name		= "greybus_module",
+	.release	= gb_module_release,
+};
+
+struct gb_module *gb_module_create(struct gb_host_device *hd, u8 module_id,
+				   size_t num_interfaces)
+{
+	struct gb_interface *intf;
+	struct gb_module *module;
+	int i;
+
+	module = kzalloc_flex(*module, interfaces, num_interfaces);
+	if (!module)
+		return NULL;
+
+	module->hd = hd;
+	module->module_id = module_id;
+	module->num_interfaces = num_interfaces;
+
+	module->dev.parent = &hd->dev;
+	module->dev.bus = &greybus_bus_type;
+	module->dev.type = &greybus_module_type;
+	module->dev.groups = module_groups;
+	module->dev.dma_mask = hd->dev.dma_mask;
+	device_initialize(&module->dev);
+	dev_set_name(&module->dev, "%d-%u", hd->bus_id, module_id);
+
+	trace_gb_module_create(module);
+
+	for (i = 0; i < num_interfaces; ++i) {
+		intf = gb_interface_create(module, module_id + i);
+		if (!intf) {
+			dev_err(&module->dev, "failed to create interface %u\n",
+				module_id + i);
+			goto err_put_interfaces;
+		}
+		module->interfaces[i] = intf;
+	}
+
+	return module;
+
+err_put_interfaces:
+	for (--i; i >= 0; --i)
+		gb_interface_put(module->interfaces[i]);
+
+	put_device(&module->dev);
+
+	return NULL;
+}
+
+/*
+ * Register and enable an interface after first attempting to activate it.
+ */
+static void gb_module_register_interface(struct gb_interface *intf)
+{
+	struct gb_module *module = intf->module;
+	u8 intf_id = intf->interface_id;
+	int ret;
+
+	mutex_lock(&intf->mutex);
+
+	ret = gb_interface_activate(intf);
+	if (ret) {
+		if (intf->type != GB_INTERFACE_TYPE_DUMMY) {
+			dev_err(&module->dev,
+				"failed to activate interface %u: %d\n",
+				intf_id, ret);
+		}
+
+		gb_interface_add(intf);
+		goto err_unlock;
+	}
+
+	ret = gb_interface_add(intf);
+	if (ret)
+		goto err_interface_deactivate;
+
+	ret = gb_interface_enable(intf);
+	if (ret) {
+		dev_err(&module->dev, "failed to enable interface %u: %d\n",
+			intf_id, ret);
+		goto err_interface_deactivate;
+	}
+
+	mutex_unlock(&intf->mutex);
+
+	return;
+
+err_interface_deactivate:
+	gb_interface_deactivate(intf);
+err_unlock:
+	mutex_unlock(&intf->mutex);
+}
+
+static void gb_module_deregister_interface(struct gb_interface *intf)
+{
+	/* Mark as disconnected to prevent I/O during disable. */
+	if (intf->module->disconnected)
+		intf->disconnected = true;
+
+	mutex_lock(&intf->mutex);
+	intf->removed = true;
+	gb_interface_disable(intf);
+	gb_interface_deactivate(intf);
+	mutex_unlock(&intf->mutex);
+
+	gb_interface_del(intf);
+}
+
+/* Register a module and its interfaces. */
+int gb_module_add(struct gb_module *module)
+{
+	size_t i;
+	int ret;
+
+	ret = device_add(&module->dev);
+	if (ret) {
+		dev_err(&module->dev, "failed to register module: %d\n", ret);
+		return ret;
+	}
+
+	trace_gb_module_add(module);
+
+	for (i = 0; i < module->num_interfaces; ++i)
+		gb_module_register_interface(module->interfaces[i]);
+
+	return 0;
+}
+
+/* Deregister a module and its interfaces. */
+void gb_module_del(struct gb_module *module)
+{
+	size_t i;
+
+	for (i = 0; i < module->num_interfaces; ++i)
+		gb_module_deregister_interface(module->interfaces[i]);
+
+	trace_gb_module_del(module);
+
+	device_del(&module->dev);
+}
+
+void gb_module_put(struct gb_module *module)
+{
+	size_t i;
+
+	for (i = 0; i < module->num_interfaces; ++i)
+		gb_interface_put(module->interfaces[i]);
+
+	put_device(&module->dev);
+}