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, 178 insertions, 0 deletions

diff --git a/Documentation/ABI/testing/sysfs-class-mic b/Documentation/ABI/testing/sysfs-class-mic
new file mode 100644
index 000000000..5e5f36d10
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-class-mic
@@ -0,0 +1,178 @@
+What:		/sys/class/mic/
+Date:		October 2013
+KernelVersion:	3.13
+Contact:	Sudeep Dutt <sudeep.dutt@intel.com>
+Description:
+		The mic class directory belongs to Intel MIC devices and
+		provides information per MIC device. An Intel MIC device is a
+		PCIe form factor add-in Coprocessor card based on the Intel Many
+		Integrated Core (MIC) architecture that runs a Linux OS.
+
+What:		/sys/class/mic/mic<X>
+Date:		October 2013
+KernelVersion:	3.13
+Contact:	Sudeep Dutt <sudeep.dutt@intel.com>
+Description:
+		The directories /sys/class/mic/mic0, /sys/class/mic/mic1 etc.,
+		represent MIC devices (0,1,..etc). Each directory has
+		information specific to that MIC device.
+
+What:		/sys/class/mic/mic<X>/family
+Date:		October 2013
+KernelVersion:	3.13
+Contact:	Sudeep Dutt <sudeep.dutt@intel.com>
+Description:
+		Provides information about the Coprocessor family for an Intel
+		MIC device. For example - "x100"
+
+What:		/sys/class/mic/mic<X>/stepping
+Date:		October 2013
+KernelVersion:	3.13
+Contact:	Sudeep Dutt <sudeep.dutt@intel.com>
+Description:
+		Provides information about the silicon stepping for an Intel
+		MIC device. For example - "A0" or "B0"
+
+What:		/sys/class/mic/mic<X>/state
+Date:		October 2013
+KernelVersion:	3.13
+Contact:	Sudeep Dutt <sudeep.dutt@intel.com>
+Description:
+		When read, this entry provides the current state of an Intel
+		MIC device in the context of the card OS. Possible values that
+		will be read are:
+
+
+		===============  ===============================================
+		"ready"		 The MIC device is ready to boot the card OS.
+				 On reading this entry after an OSPM resume,
+				 a "boot" has to be written to this entry if
+				 the card was previously shutdown during OSPM
+				 suspend.
+		"booting"	 The MIC device has initiated booting a card OS.
+		"online"	 The MIC device has completed boot and is online
+		"shutting_down"	 The card OS is shutting down.
+		"resetting"	 A reset has been initiated for the MIC device
+		"reset_failed"	 The MIC device has failed to reset.
+		===============  ===============================================
+
+		When written, this sysfs entry triggers different state change
+		operations depending upon the current state of the card OS.
+		Acceptable values are:
+
+
+		==========  ===================================================
+		"boot"      Boot the card OS image specified by the combination
+			    of firmware, ramdisk, cmdline and bootmode
+			    sysfs entries.
+		"reset"     Initiates device reset.
+		"shutdown"  Initiates card OS shutdown.
+		==========  ===================================================
+
+What:		/sys/class/mic/mic<X>/shutdown_status
+Date:		October 2013
+KernelVersion:	3.13
+Contact:	Sudeep Dutt <sudeep.dutt@intel.com>
+Description:
+		An Intel MIC device runs a Linux OS during its operation. This
+		OS can shutdown because of various reasons. When read, this
+		entry provides the status on why the card OS was shutdown.
+		Possible values are:
+
+		==========  ===================================================
+		"nop"       shutdown status is not applicable, when the card OS
+			    is "online"
+		"crashed"   Shutdown because of a HW or SW crash.
+		"halted"    Shutdown because of a halt command.
+		"poweroff"  Shutdown because of a poweroff command.
+		"restart"   Shutdown because of a restart command.
+		==========  ===================================================
+
+What:		/sys/class/mic/mic<X>/cmdline
+Date:		October 2013
+KernelVersion:	3.13
+Contact:	Sudeep Dutt <sudeep.dutt@intel.com>
+Description:
+		An Intel MIC device runs a Linux OS during its operation. Before
+		booting this card OS, it is possible to pass kernel command line
+		options to configure various features in it, similar to
+		self-bootable machines. When read, this entry provides
+		information about the current kernel command line options set to
+		boot the card OS. This entry can be written to change the
+		existing kernel command line options. Typically, the user would
+		want to read the current command line options, append new ones
+		or modify existing ones and then write the whole kernel command
+		line back to this entry.
+
+What:		/sys/class/mic/mic<X>/firmware
+Date:		October 2013
+KernelVersion:	3.13
+Contact:	Sudeep Dutt <sudeep.dutt@intel.com>
+Description:
+		When read, this sysfs entry provides the path name under
+		/lib/firmware/ where the firmware image to be booted on the
+		card can be found. The entry can be written to change the
+		firmware image location under /lib/firmware/.
+
+What:		/sys/class/mic/mic<X>/ramdisk
+Date:		October 2013
+KernelVersion:	3.13
+Contact:	Sudeep Dutt <sudeep.dutt@intel.com>
+Description:
+		When read, this sysfs entry provides the path name under
+		/lib/firmware/ where the ramdisk image to be used during card
+		OS boot can be found. The entry can be written to change
+		the ramdisk image location under /lib/firmware/.
+
+What:		/sys/class/mic/mic<X>/bootmode
+Date:		October 2013
+KernelVersion:	3.13
+Contact:	Sudeep Dutt <sudeep.dutt@intel.com>
+Description:
+		When read, this sysfs entry provides the current bootmode for
+		the card. This sysfs entry can be written with the following
+		valid strings:
+		a) linux - Boot a Linux image.
+		b) flash - Boot an image for flash updates.
+
+What:		/sys/class/mic/mic<X>/log_buf_addr
+Date:		October 2013
+KernelVersion:	3.13
+Contact:	Sudeep Dutt <sudeep.dutt@intel.com>
+Description:
+		An Intel MIC device runs a Linux OS during its operation. For
+		debugging purpose and early kernel boot messages, the user can
+		access the card OS log buffer via debugfs. When read, this entry
+		provides the kernel virtual address of the buffer where the card
+		OS log buffer can be read. This entry is written by the host
+		configuration daemon to set the log buffer address. The correct
+		log buffer address to be written can be found in the System.map
+		file of the card OS.
+
+What:		/sys/class/mic/mic<X>/log_buf_len
+Date:		October 2013
+KernelVersion:	3.13
+Contact:	Sudeep Dutt <sudeep.dutt@intel.com>
+Description:
+		An Intel MIC device runs a Linux OS during its operation. For
+		debugging purpose and early kernel boot messages, the user can
+		access the card OS log buffer via debugfs. When read, this entry
+		provides the kernel virtual address where the card OS log buffer
+		length can be read. This entry is written by host configuration
+		daemon to set the log buffer length address. The correct log
+		buffer length address to be written can be found in the
+		System.map file of the card OS.
+
+What:		/sys/class/mic/mic<X>/heartbeat_enable
+Date:		March 2015
+KernelVersion:	4.4
+Contact:	Ashutosh Dixit <ashutosh.dixit@intel.com>
+Description:
+		The MIC drivers detect and inform user space about card crashes
+		via a heartbeat mechanism (see the description of
+		shutdown_status above). User space can turn off this
+		notification by setting heartbeat_enable to 0 and enable it by
+		setting this entry to 1. If this notification is disabled it is
+		the responsibility of user space to detect card crashes via
+		alternative means such as a network ping. This setting is
+		enabled by default.