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, 77 insertions, 0 deletions

diff --git a/net/sunrpc/Kconfig b/net/sunrpc/Kconfig
new file mode 100644
index 000000000..e7808e571
--- /dev/null
+++ b/net/sunrpc/Kconfig
@@ -0,0 +1,77 @@
+# SPDX-License-Identifier: GPL-2.0-only
+config SUNRPC
+	tristate
+	depends on MULTIUSER
+
+config SUNRPC_GSS
+	tristate
+	select OID_REGISTRY
+	depends on MULTIUSER
+
+config SUNRPC_BACKCHANNEL
+	bool
+	depends on SUNRPC
+
+config SUNRPC_SWAP
+	bool
+	depends on SUNRPC
+
+config RPCSEC_GSS_KRB5
+	tristate "Secure RPC: Kerberos V mechanism"
+	depends on SUNRPC && CRYPTO
+	default y
+	select SUNRPC_GSS
+	select CRYPTO_KRB5
+	help
+	  Choose Y here to enable Secure RPC using the Kerberos version 5
+	  GSS-API mechanism (RFC 1964).
+
+	  Secure RPC calls with Kerberos require an auxiliary user-space
+	  daemon which may be found in the Linux nfs-utils package
+	  available from http://linux-nfs.org/.  In addition, user-space
+	  Kerberos support should be installed.
+
+	  If unsure, say Y.
+
+config SUNRPC_DEBUG
+	bool "RPC: Enable dprintk debugging"
+	depends on SUNRPC && SYSCTL
+	select DEBUG_FS
+	help
+	  This option enables a sysctl-based debugging interface
+	  that is be used by the 'rpcdebug' utility to turn on or off
+	  logging of different aspects of the kernel RPC activity.
+
+	  Disabling this option will make your kernel slightly smaller,
+	  but makes troubleshooting NFS issues significantly harder.
+
+	  If unsure, say Y.
+
+config SUNRPC_DEBUG_TRACE
+	bool "RPC: Send dfprintk() output to the trace buffer"
+	depends on SUNRPC_DEBUG && TRACING
+	default n
+	help
+          dprintk() output can be voluminous, which can overwhelm the
+          kernel's logging facility as it must be sent to the console.
+          This option causes dprintk() output to go to the trace buffer
+          instead of the kernel log.
+
+          This will cause warnings about trace_printk() being used to be
+          logged at boot time, so say N unless you are debugging a problem
+          with sunrpc-based clients or services.
+
+config SUNRPC_XPRT_RDMA
+	tristate "RPC-over-RDMA transport"
+	depends on SUNRPC && INFINIBAND && INFINIBAND_ADDR_TRANS
+	default SUNRPC && INFINIBAND
+	select SG_POOL
+	help
+	  This option allows the NFS client and server to use RDMA
+	  transports (InfiniBand, iWARP, or RoCE).
+
+	  To compile this support as a module, choose M. The module
+	  will be called rpcrdma.ko.
+
+	  If unsure, or you know there is no RDMA capability on your
+	  hardware platform, say N.