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, 245 insertions, 0 deletions

diff --git a/include/drm/drm_client.h b/include/drm/drm_client.h
new file mode 100644
index 000000000..49a21f3dc
--- /dev/null
+++ b/include/drm/drm_client.h
@@ -0,0 +1,245 @@
+/* SPDX-License-Identifier: GPL-2.0 or MIT */
+
+#ifndef _DRM_CLIENT_H_
+#define _DRM_CLIENT_H_
+
+#include <linux/iosys-map.h>
+#include <linux/lockdep.h>
+#include <linux/mutex.h>
+#include <linux/types.h>
+
+#include <drm/drm_connector.h>
+#include <drm/drm_crtc.h>
+
+struct drm_client_dev;
+struct drm_device;
+struct drm_file;
+struct drm_framebuffer;
+struct drm_gem_object;
+struct drm_minor;
+struct module;
+
+/**
+ * struct drm_client_funcs - DRM client callbacks
+ */
+struct drm_client_funcs {
+	/**
+	 * @owner: The module owner
+	 */
+	struct module *owner;
+
+	/**
+	 * @free:
+	 *
+	 * Called when the client gets unregistered. Implementations should
+	 * release all client-specific data and free the memory.
+	 *
+	 * This callback is optional.
+	 */
+	void (*free)(struct drm_client_dev *client);
+
+	/**
+	 * @unregister:
+	 *
+	 * Called when &drm_device is unregistered. The client should respond by
+	 * releasing its resources using drm_client_release().
+	 *
+	 * This callback is optional.
+	 */
+	void (*unregister)(struct drm_client_dev *client);
+
+	/**
+	 * @restore:
+	 *
+	 * Called on drm_lastclose(). The first client instance in the list that
+	 * returns zero gets the privilege to restore and no more clients are
+	 * called. This callback is not called after @unregister has been called.
+	 *
+	 * Note that the core does not guarantee exclusion against concurrent
+	 * drm_open(). Clients need to ensure this themselves, for example by
+	 * using drm_master_internal_acquire() and drm_master_internal_release().
+	 *
+	 * If the caller passes force, the client should ignore any present DRM
+	 * master and restore the display anyway.
+	 *
+	 * This callback is optional.
+	 */
+	int (*restore)(struct drm_client_dev *client, bool force);
+
+	/**
+	 * @hotplug:
+	 *
+	 * Called on drm_kms_helper_hotplug_event().
+	 * This callback is not called after @unregister has been called.
+	 *
+	 * This callback is optional.
+	 */
+	int (*hotplug)(struct drm_client_dev *client);
+
+	/**
+	 * @suspend:
+	 *
+	 * Called when suspending the device.
+	 *
+	 * This callback is optional.
+	 */
+	int (*suspend)(struct drm_client_dev *client);
+
+	/**
+	 * @resume:
+	 *
+	 * Called when resuming the device from suspend.
+	 *
+	 * This callback is optional.
+	 */
+	int (*resume)(struct drm_client_dev *client);
+};
+
+/**
+ * struct drm_client_dev - DRM client instance
+ */
+struct drm_client_dev {
+	/**
+	 * @dev: DRM device
+	 */
+	struct drm_device *dev;
+
+	/**
+	 * @name: Name of the client.
+	 */
+	const char *name;
+
+	/**
+	 * @list:
+	 *
+	 * List of all clients of a DRM device, linked into
+	 * &drm_device.clientlist. Protected by &drm_device.clientlist_mutex.
+	 */
+	struct list_head list;
+
+	/**
+	 * @funcs: DRM client functions (optional)
+	 */
+	const struct drm_client_funcs *funcs;
+
+	/**
+	 * @file: DRM file
+	 */
+	struct drm_file *file;
+
+	/**
+	 * @modeset_mutex: Protects @modesets.
+	 */
+	struct mutex modeset_mutex;
+
+	/**
+	 * @modesets: CRTC configurations
+	 */
+	struct drm_mode_set *modesets;
+
+	/**
+	 * @suspended:
+	 *
+	 * The client has been suspended.
+	 */
+	bool suspended;
+
+	/**
+	 * @hotplug_pending:
+	 *
+	 * A hotplug event has been received while the client was suspended.
+	 * Try again on resume.
+	 */
+	bool hotplug_pending;
+
+	/**
+	 * @hotplug_failed:
+	 *
+	 * Set by client hotplug helpers if the hotplugging failed
+	 * before. It is usually not tried again.
+	 */
+	bool hotplug_failed;
+};
+
+int drm_client_init(struct drm_device *dev, struct drm_client_dev *client,
+		    const char *name, const struct drm_client_funcs *funcs);
+void drm_client_release(struct drm_client_dev *client);
+void drm_client_register(struct drm_client_dev *client);
+
+/**
+ * struct drm_client_buffer - DRM client buffer
+ */
+struct drm_client_buffer {
+	/**
+	 * @client: DRM client
+	 */
+	struct drm_client_dev *client;
+
+	/**
+	 * @gem: GEM object backing this buffer
+	 *
+	 * FIXME: The DRM framebuffer holds a reference on its GEM
+	 * buffer objects. Do not use this field in new code and
+	 * update existing users.
+	 */
+	struct drm_gem_object *gem;
+
+	/**
+	 * @map: Virtual address for the buffer
+	 */
+	struct iosys_map map;
+
+	/**
+	 * @fb: DRM framebuffer
+	 */
+	struct drm_framebuffer *fb;
+};
+
+struct drm_client_buffer *
+drm_client_buffer_create(struct drm_client_dev *client, u32 width, u32 height,
+			 u32 format, u32 handle, u32 pitch);
+struct drm_client_buffer *
+drm_client_buffer_create_dumb(struct drm_client_dev *client, u32 width, u32 height, u32 format);
+void drm_client_buffer_delete(struct drm_client_buffer *buffer);
+int drm_client_buffer_flush(struct drm_client_buffer *buffer, struct drm_rect *rect);
+int drm_client_buffer_vmap_local(struct drm_client_buffer *buffer,
+				 struct iosys_map *map_copy);
+void drm_client_buffer_vunmap_local(struct drm_client_buffer *buffer);
+int drm_client_buffer_vmap(struct drm_client_buffer *buffer,
+			   struct iosys_map *map);
+void drm_client_buffer_vunmap(struct drm_client_buffer *buffer);
+
+int drm_client_modeset_create(struct drm_client_dev *client);
+void drm_client_modeset_free(struct drm_client_dev *client);
+int drm_client_modeset_probe(struct drm_client_dev *client, unsigned int width, unsigned int height);
+bool drm_client_rotation(struct drm_mode_set *modeset, unsigned int *rotation);
+int drm_client_modeset_check(struct drm_client_dev *client);
+int drm_client_modeset_commit_locked(struct drm_client_dev *client);
+int drm_client_modeset_commit(struct drm_client_dev *client);
+int drm_client_modeset_dpms(struct drm_client_dev *client, int mode);
+int drm_client_modeset_wait_for_vblank(struct drm_client_dev *client, unsigned int crtc_index);
+
+/**
+ * drm_client_for_each_modeset() - Iterate over client modesets
+ * @modeset: &drm_mode_set loop cursor
+ * @client: DRM client
+ */
+#define drm_client_for_each_modeset(modeset, client) \
+	for (({ lockdep_assert_held(&(client)->modeset_mutex); }), \
+	     modeset = (client)->modesets; modeset->crtc; modeset++)
+
+/**
+ * drm_client_for_each_connector_iter - connector_list iterator macro
+ * @connector: &struct drm_connector pointer used as cursor
+ * @iter: &struct drm_connector_list_iter
+ *
+ * This iterates the connectors that are useable for internal clients (excludes
+ * writeback connectors).
+ *
+ * For more info see drm_for_each_connector_iter().
+ */
+#define drm_client_for_each_connector_iter(connector, iter) \
+	drm_for_each_connector_iter(connector, iter) \
+		if (connector->connector_type != DRM_MODE_CONNECTOR_WRITEBACK)
+
+#endif