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, 73 insertions, 0 deletions

diff --git a/drivers/net/fddi/Kconfig b/drivers/net/fddi/Kconfig
new file mode 100644
index 000000000..846bf41c2
--- /dev/null
+++ b/drivers/net/fddi/Kconfig
@@ -0,0 +1,73 @@
+# SPDX-License-Identifier: GPL-2.0-only
+#
+# FDDI network device configuration
+#
+
+config FDDI
+	tristate "FDDI driver support"
+	depends on PCI || EISA || TC
+	help
+	  Fiber Distributed Data Interface is a high speed local area network
+	  design; essentially a replacement for high speed Ethernet. FDDI can
+	  run over copper or fiber. If you are connected to such a network and
+	  want a driver for the FDDI card in your computer, say Y here (and
+	  then also Y to the driver for your FDDI card, below). Most people
+	  will say N.
+
+if FDDI
+
+config DEFZA
+	tristate "DEC FDDIcontroller 700/700-C (DEFZA-xx) support"
+	depends on FDDI && TC
+	help
+	  This is support for the DEC FDDIcontroller 700 (DEFZA-AA, fiber)
+	  and 700-C (DEFZA-CA, copper) TURBOchannel network cards which
+	  can connect you to a local FDDI network.
+
+	  To compile this driver as a module, choose M here: the module
+	  will be called defza.  If unsure, say N.
+
+config DEFXX
+	tristate "Digital DEFTA/DEFEA/DEFPA adapter support"
+	depends on FDDI && (PCI || EISA || TC)
+	help
+	  This is support for the DIGITAL series of TURBOchannel (DEFTA),
+	  EISA (DEFEA) and PCI (DEFPA) controllers which can connect you
+	  to a local FDDI network.
+
+	  To compile this driver as a module, choose M here: the module
+	  will be called defxx.  If unsure, say N.
+
+config SKFP
+	tristate "SysKonnect FDDI PCI support"
+	depends on FDDI && PCI
+	select BITREVERSE
+	help
+	  Say Y here if you have a SysKonnect FDDI PCI adapter.
+	  The following adapters are supported by this driver:
+	  - SK-5521 (SK-NET FDDI-UP)
+	  - SK-5522 (SK-NET FDDI-UP DAS)
+	  - SK-5541 (SK-NET FDDI-FP)
+	  - SK-5543 (SK-NET FDDI-LP)
+	  - SK-5544 (SK-NET FDDI-LP DAS)
+	  - SK-5821 (SK-NET FDDI-UP64)
+	  - SK-5822 (SK-NET FDDI-UP64 DAS)
+	  - SK-5841 (SK-NET FDDI-FP64)
+	  - SK-5843 (SK-NET FDDI-LP64)
+	  - SK-5844 (SK-NET FDDI-LP64 DAS)
+	  - Netelligent 100 FDDI DAS Fibre SC
+	  - Netelligent 100 FDDI SAS Fibre SC
+	  - Netelligent 100 FDDI DAS UTP
+	  - Netelligent 100 FDDI SAS UTP
+	  - Netelligent 100 FDDI SAS Fibre MIC
+
+	  Read <file:Documentation/networking/device_drivers/fddi/skfp.rst>
+	  for information about the driver.
+
+	  Questions concerning this driver can be addressed to:
+	  <linux@syskonnect.de>
+
+	  To compile this driver as a module, choose M here: the module
+	  will be called skfp.  This is recommended.
+
+endif # FDDI