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, 166 insertions, 0 deletions

diff --git a/Documentation/ABI/testing/sysfs-tty b/Documentation/ABI/testing/sysfs-tty
new file mode 100644
index 000000000..895c47f05
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-tty
@@ -0,0 +1,166 @@
+What:		/sys/class/tty/console/active
+Date:		Nov 2010
+Contact:	Kay Sievers <kay.sievers@vrfy.org>
+Description:
+		 Shows the list of currently configured
+		 console devices, like 'tty1 ttyS0'.
+		 The last entry in the file is the active
+		 device connected to /dev/console.
+		 The file supports poll() to detect virtual
+		 console switches.
+
+What:		/sys/class/tty/tty<x>/active
+Date:		Nov 2010
+Contact:	Kay Sievers <kay.sievers@vrfy.org>
+Description:
+		 Shows the currently active virtual console
+		 device, like 'tty1'.
+		 The file supports poll() to detect virtual
+		 console switches.
+
+What:		/sys/class/tty/ttyS<x>/uartclk
+Date:		Sep 2012
+Contact:	Tomas Hlavacek <tmshlvck@gmail.com>
+Description:
+		 Shows the current uartclk value associated with the
+		 UART port in serial_core, that is bound to TTY like ttyS0.
+		 uartclk = 16 * baud_base
+
+		 These sysfs values expose the TIOCGSERIAL interface via
+		 sysfs rather than via ioctls.
+
+What:		/sys/class/tty/ttyS<x>/type
+Date:		October 2012
+Contact:	Alan Cox <alan@linux.intel.com>
+Description:
+		 Shows the current tty type for this port.
+
+		 These sysfs values expose the TIOCGSERIAL interface via
+		 sysfs rather than via ioctls.
+
+What:		/sys/class/tty/ttyS<x>/line
+Date:		October 2012
+Contact:	Alan Cox <alan@linux.intel.com>
+Description:
+		 Shows the current tty line number for this port.
+
+		 These sysfs values expose the TIOCGSERIAL interface via
+		 sysfs rather than via ioctls.
+
+What:		/sys/class/tty/ttyS<x>/port
+Date:		October 2012
+Contact:	Alan Cox <alan@linux.intel.com>
+Description:
+		 Shows the current tty port I/O address for this port.
+
+		 These sysfs values expose the TIOCGSERIAL interface via
+		 sysfs rather than via ioctls.
+
+What:		/sys/class/tty/ttyS<x>/irq
+Date:		October 2012
+Contact:	Alan Cox <alan@linux.intel.com>
+Description:
+		 Shows the current primary interrupt for this port.
+
+		 These sysfs values expose the TIOCGSERIAL interface via
+		 sysfs rather than via ioctls.
+
+What:		/sys/class/tty/ttyS<x>/flags
+Date:		October 2012
+Contact:	Alan Cox <alan@linux.intel.com>
+Description:
+		 Show the tty port status flags for this port.
+
+		 These sysfs values expose the TIOCGSERIAL interface via
+		 sysfs rather than via ioctls.
+
+What:		/sys/class/tty/ttyS<x>/xmit_fifo_size
+Date:		October 2012
+Contact:	Alan Cox <alan@linux.intel.com>
+Description:
+		 Show the transmit FIFO size for this port.
+
+		 These sysfs values expose the TIOCGSERIAL interface via
+		 sysfs rather than via ioctls.
+
+What:		/sys/class/tty/ttyS<x>/close_delay
+Date:		October 2012
+Contact:	Alan Cox <alan@linux.intel.com>
+Description:
+		Show the closing delay time for this port in centiseconds.
+
+		These sysfs values expose the TIOCGSERIAL interface via
+		sysfs rather than via ioctls.
+
+What:		/sys/class/tty/ttyS<x>/closing_wait
+Date:		October 2012
+Contact:	Alan Cox <alan@linux.intel.com>
+Description:
+		Show the close wait time for this port in centiseconds.
+
+		Waiting forever is represented as 0. If waiting on close is
+		disabled then the value is 65535.
+
+		These sysfs values expose the TIOCGSERIAL interface via
+		sysfs rather than via ioctls.
+
+What:		/sys/class/tty/ttyS<x>/custom_divisor
+Date:		October 2012
+Contact:	Alan Cox <alan@linux.intel.com>
+Description:
+		 Show the custom divisor if any that is set on this port.
+
+		 These sysfs values expose the TIOCGSERIAL interface via
+		 sysfs rather than via ioctls.
+
+What:		/sys/class/tty/ttyS<x>/io_type
+Date:		October 2012
+Contact:	Alan Cox <alan@linux.intel.com>
+Description:
+		 Show the I/O type that is to be used with the iomem base
+		 address.
+
+		 These sysfs values expose the TIOCGSERIAL interface via
+		 sysfs rather than via ioctls.
+
+What:		/sys/class/tty/ttyS<x>/iomem_base
+Date:		October 2012
+Contact:	Alan Cox <alan@linux.intel.com>
+Description:
+		 The I/O memory base for this port.
+
+		 These sysfs values expose the TIOCGSERIAL interface via
+		 sysfs rather than via ioctls.
+
+What:		/sys/class/tty/ttyS<x>/iomem_reg_shift
+Date:		October 2012
+Contact:	Alan Cox <alan@linux.intel.com>
+Description:
+		 Show the register shift indicating the spacing to be used
+		 for accesses on this iomem address.
+
+		 These sysfs values expose the TIOCGSERIAL interface via
+		 sysfs rather than via ioctls.
+
+What:		/sys/class/tty/ttyS<x>/rx_trig_bytes
+Date:		May 2014
+Contact:	Yoshihiro YUNOMAE <yoshihiro.yunomae.ez@hitachi.com>
+Description:
+		 Shows current RX interrupt trigger bytes or sets the
+		 user specified value to change it for the FIFO buffer.
+		 Users can show or set this value regardless of opening the
+		 serial device file or not.
+
+		 The RX trigger can be set one of four kinds of values for UART
+		 serials. When users input a meaning less value to this I/F,
+		 the RX trigger is changed to the nearest lower value for the
+		 device specification. For example, when user sets 7bytes on
+		 16550A, which has 1/4/8/14 bytes trigger, the RX trigger is
+		 automatically changed to 4 bytes.
+
+What:		/sys/class/tty/ttyS<x>/console
+Date:		February 2020
+Contact:	Andy Shevchenko <andriy.shevchenko@linux.intel.com>
+Description:
+		 Allows user to detach or attach back the given device as
+		 kernel console. It shows and accepts a boolean variable.