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, 146 insertions, 0 deletions

diff --git a/Documentation/ABI/testing/sysfs-class-rtrs-client b/Documentation/ABI/testing/sysfs-class-rtrs-client
new file mode 100644
index 000000000..fecc59d1b
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-class-rtrs-client
@@ -0,0 +1,146 @@
+What:		/sys/class/rtrs-client
+Date:		Feb 2020
+KernelVersion:	5.7
+Contact:	Jack Wang <jinpu.wang@cloud.ionos.com> Danil Kipnis <danil.kipnis@cloud.ionos.com>
+Description:	When a user of RTRS API creates a new session, a directory entry with
+		the name of that session is created under /sys/class/rtrs-client/<session-name>/
+
+What:		/sys/class/rtrs-client/<session-name>/add_path
+Date:		Feb 2020
+KernelVersion:	5.7
+Contact:	Jack Wang <jinpu.wang@cloud.ionos.com> Danil Kipnis <danil.kipnis@cloud.ionos.com>
+Description:	RW, adds a new path (connection) to an existing session. Expected format is the
+		following::
+
+		    <[source addr,]destination addr>
+		    *addr ::= [ ip:<ipv4|ipv6> | gid:<gid> ]
+
+What:		/sys/class/rtrs-client/<session-name>/max_reconnect_attempts
+Date:		Feb 2020
+KernelVersion:	5.7
+Contact:	Jack Wang <jinpu.wang@cloud.ionos.com> Danil Kipnis <danil.kipnis@cloud.ionos.com>
+Description:	Maximum number reconnect attempts the client should make before giving up
+		after connection breaks unexpectedly.
+
+What:		/sys/class/rtrs-client/<session-name>/mp_policy
+Date:		Feb 2020
+KernelVersion:	5.7
+Contact:	Jack Wang <jinpu.wang@cloud.ionos.com> Danil Kipnis <danil.kipnis@cloud.ionos.com>
+Description:	Multipath policy specifies which path should be selected on each IO:
+
+		round-robin (0):
+		    select path in per CPU round-robin manner.
+
+		min-inflight (1):
+		    select path with minimum inflights.
+
+		min-latency (2):
+		    select path with minimum latency.
+
+What:		/sys/class/rtrs-client/<session-name>/paths/
+Date:		Feb 2020
+KernelVersion:	5.7
+Contact:	Jack Wang <jinpu.wang@cloud.ionos.com> Danil Kipnis <danil.kipnis@cloud.ionos.com>
+Description:	Each path belonging to a given session is listed here by its source and
+		destination address. When a new path is added to a session by writing to
+		the "add_path" entry, a directory <src@dst> is created.
+
+What:		/sys/class/rtrs-client/<session-name>/paths/<src@dst>/state
+Date:		Feb 2020
+KernelVersion:	5.7
+Contact:	Jack Wang <jinpu.wang@cloud.ionos.com> Danil Kipnis <danil.kipnis@cloud.ionos.com>
+Description:	RO, Contains "connected" if the session is connected to the peer and fully
+		functional.  Otherwise the file contains "disconnected"
+
+What:		/sys/class/rtrs-client/<session-name>/paths/<src@dst>/reconnect
+Date:		Feb 2020
+KernelVersion:	5.7
+Contact:	Jack Wang <jinpu.wang@cloud.ionos.com> Danil Kipnis <danil.kipnis@cloud.ionos.com>
+Description:	Write "1" to the file in order to reconnect the path.
+		Operation is blocking and returns 0 if reconnect was successful.
+
+What:		/sys/class/rtrs-client/<session-name>/paths/<src@dst>/disconnect
+Date:		Feb 2020
+KernelVersion:	5.7
+Contact:	Jack Wang <jinpu.wang@cloud.ionos.com> Danil Kipnis <danil.kipnis@cloud.ionos.com>
+Description:	Write "1" to the file in order to disconnect the path.
+		Operation blocks until RTRS path is disconnected.
+
+What:		/sys/class/rtrs-client/<session-name>/paths/<src@dst>/remove_path
+Date:		Feb 2020
+KernelVersion:	5.7
+Contact:	Jack Wang <jinpu.wang@cloud.ionos.com> Danil Kipnis <danil.kipnis@cloud.ionos.com>
+Description:	Write "1" to the file in order to disconnected and remove the path
+		from the session.  Operation blocks until the path is disconnected
+		and removed from the session.
+
+What:		/sys/class/rtrs-client/<session-name>/paths/<src@dst>/hca_name
+Date:		Feb 2020
+KernelVersion:	5.7
+Contact:	Jack Wang <jinpu.wang@cloud.ionos.com> Danil Kipnis <danil.kipnis@cloud.ionos.com>
+Description:	RO, Contains the name of HCA the connection established on.
+
+What:		/sys/class/rtrs-client/<session-name>/paths/<src@dst>/hca_port
+Date:		Feb 2020
+KernelVersion:	5.7
+Contact:	Jack Wang <jinpu.wang@cloud.ionos.com> Danil Kipnis <danil.kipnis@cloud.ionos.com>
+Description:	RO, Contains the port number of active port traffic is going through.
+
+What:		/sys/class/rtrs-client/<session-name>/paths/<src@dst>/src_addr
+Date:		Feb 2020
+KernelVersion:	5.7
+Contact:	Jack Wang <jinpu.wang@cloud.ionos.com> Danil Kipnis <danil.kipnis@cloud.ionos.com>
+Description:	RO, Contains the source address of the path
+
+What:		/sys/class/rtrs-client/<session-name>/paths/<src@dst>/dst_addr
+Date:		Feb 2020
+KernelVersion:	5.7
+Contact:	Jack Wang <jinpu.wang@cloud.ionos.com> Danil Kipnis <danil.kipnis@cloud.ionos.com>
+Description:	RO, Contains the destination address of the path
+
+What:		/sys/class/rtrs-client/<session-name>/paths/<src@dst>/cur_latency
+Date:		Feb 2020
+KernelVersion:	5.7
+Contact:	Jack Wang <jinpu.wang@cloud.ionos.com> Danil Kipnis <danil.kipnis@cloud.ionos.com>
+Description:	RO, Contains the latency time calculated by the heart-beat messages.
+		Whenever the client sends heart-beat message, it checks the time gap
+		between sending the heart-beat message and receiving the ACK.
+		This value can be changed regularly.
+
+What:		/sys/class/rtrs-client/<session-name>/paths/<src@dst>/stats/reset_all
+Date:		Feb 2020
+KernelVersion:	5.7
+Contact:	Jack Wang <jinpu.wang@cloud.ionos.com> Danil Kipnis <danil.kipnis@cloud.ionos.com>
+Description:	RW, Read will return usage help, write 0 will clear all the statistics.
+
+What:		/sys/class/rtrs-client/<session-name>/paths/<src@dst>/stats/cpu_migration
+Date:		Feb 2020
+KernelVersion:	5.7
+Contact:	Jack Wang <jinpu.wang@cloud.ionos.com> Danil Kipnis <danil.kipnis@cloud.ionos.com>
+Description:	RTRS expects that each HCA IRQ is pinned to a separate CPU. If it's
+		not the case, the processing of an I/O response could be processed on a
+		different CPU than where it was originally submitted.  This file shows
+		how many interrupts where generated on a non expected CPU.
+
+		"from:"
+		    is the CPU on which the IRQ was expected, but not generated.
+		"to:"
+		    is the CPU on which the IRQ was generated, but not expected.
+
+What:		/sys/class/rtrs-client/<session-name>/paths/<src@dst>/stats/reconnects
+Date:		Feb 2020
+KernelVersion:	5.7
+Contact:	Jack Wang <jinpu.wang@cloud.ionos.com> Danil Kipnis <danil.kipnis@cloud.ionos.com>
+Description:	Contains 2 unsigned int values, the first one records number of successful
+		reconnects in the path lifetime, the second one records number of failed
+		reconnects in the path lifetime.
+
+What:		/sys/class/rtrs-client/<session-name>/paths/<src@dst>/stats/rdma
+Date:		Feb 2020
+KernelVersion:	5.7
+Contact:	Jack Wang <jinpu.wang@cloud.ionos.com> Danil Kipnis <danil.kipnis@cloud.ionos.com>
+Description:	Contains statistics regarding rdma operations and inflight operations.
+		The output consists of 6 values::
+
+		    <read-count> <read-total-size> <write-count> \
+		    <write-total-size> <inflights> <failovered>