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, 105 insertions, 0 deletions

diff --git a/net/6lowpan/Kconfig b/net/6lowpan/Kconfig
new file mode 100644
index 000000000..d8fc45949
--- /dev/null
+++ b/net/6lowpan/Kconfig
@@ -0,0 +1,105 @@
+# SPDX-License-Identifier: GPL-2.0-only
+menuconfig 6LOWPAN
+	tristate "6LoWPAN Support"
+	depends on IPV6
+	help
+	  This enables IPv6 over Low power Wireless Personal Area Network -
+	  "6LoWPAN" which is supported by IEEE 802.15.4 or Bluetooth stacks.
+
+config 6LOWPAN_DEBUGFS
+	bool "6LoWPAN debugfs support"
+	depends on 6LOWPAN
+	depends on DEBUG_FS
+	help
+	  This enables 6LoWPAN debugfs support. For example to manipulate
+	  IPHC context information at runtime.
+
+menuconfig 6LOWPAN_NHC
+	tristate "Next Header and Generic Header Compression Support"
+	depends on 6LOWPAN
+	default y
+	help
+	  Support for next header and generic header compression defined in
+	  RFC6282 and RFC7400.
+
+if 6LOWPAN_NHC
+
+config 6LOWPAN_NHC_DEST
+	tristate "Destination Options Header Support"
+	default y
+	help
+	  6LoWPAN IPv6 Destination Options Header compression according to
+	  RFC6282.
+
+config 6LOWPAN_NHC_FRAGMENT
+	tristate "Fragment Header Support"
+	default y
+	help
+	  6LoWPAN IPv6 Fragment Header compression according to RFC6282.
+
+config 6LOWPAN_NHC_HOP
+	tristate "Hop-by-Hop Options Header Support"
+	default y
+	help
+	  6LoWPAN IPv6 Hop-by-Hop Options Header compression according to
+	  RFC6282.
+
+config 6LOWPAN_NHC_IPV6
+	tristate "IPv6 Header Support"
+	default y
+	help
+	  6LoWPAN IPv6 Header compression according to RFC6282.
+
+config 6LOWPAN_NHC_MOBILITY
+	tristate "Mobility Header Support"
+	default y
+	help
+	  6LoWPAN IPv6 Mobility Header compression according to RFC6282.
+
+config 6LOWPAN_NHC_ROUTING
+	tristate "Routing Header Support"
+	default y
+	help
+	  6LoWPAN IPv6 Routing Header compression according to RFC6282.
+
+config 6LOWPAN_NHC_UDP
+	tristate "UDP Header Support"
+	default y
+	help
+	  6LoWPAN IPv6 UDP Header compression according to RFC6282.
+
+config 6LOWPAN_GHC_EXT_HDR_HOP
+	tristate "GHC Hop-by-Hop Options Header Support"
+	help
+	  6LoWPAN IPv6 Hop-by-Hop option generic header compression according
+	  to RFC7400.
+
+config 6LOWPAN_GHC_UDP
+	tristate "GHC UDP Support"
+	help
+	  6LoWPAN IPv6 UDP generic header compression according to RFC7400.
+
+config 6LOWPAN_GHC_ICMPV6
+	tristate "GHC ICMPv6 Support"
+	help
+	  6LoWPAN IPv6 ICMPv6 generic header compression according to RFC7400.
+
+config 6LOWPAN_GHC_EXT_HDR_DEST
+	tristate "GHC Destination Options Header Support"
+	help
+	  6LoWPAN IPv6 destination option generic header compression according
+	  to RFC7400.
+
+config 6LOWPAN_GHC_EXT_HDR_FRAG
+	tristate "GHC Fragmentation Options Header Support"
+	help
+	  6LoWPAN IPv6 fragmentation option generic header compression
+	  according to RFC7400.
+
+config 6LOWPAN_GHC_EXT_HDR_ROUTE
+	tristate "GHC Routing Options Header Support"
+	help
+	  6LoWPAN IPv6 routing option generic header compression according
+	  to RFC7400.
+
+endif