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, 52 insertions, 0 deletions

diff --git a/arch/parisc/math-emu/fpbits.h b/arch/parisc/math-emu/fpbits.h
new file mode 100644
index 000000000..b46bddb9a
--- /dev/null
+++ b/arch/parisc/math-emu/fpbits.h
@@ -0,0 +1,52 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * Linux/PA-RISC Project (http://www.parisc-linux.org/)
+ *
+ * Floating-point emulation code
+ *  Copyright (C) 2001 Hewlett-Packard (Paul Bame) <bame@debian.org>
+ */
+
+#ifdef __NO_PA_HDRS
+    PA header file -- do not include this header file for non-PA builds.
+#endif
+
+
+/*
+ *  These macros are designed to be portable to all machines that have
+ *  a wordsize greater than or equal to 32 bits that support the portable
+ *  C compiler and the standard C preprocessor.  Wordsize (default 32)
+ *  and bitfield assignment (default left-to-right,  unlike VAX, PDP-11)
+ *  should be predefined using the constants HOSTWDSZ and BITFRL and
+ *  the C compiler "-D" flag (e.g., -DHOSTWDSZ=36 -DBITFLR for the DEC-20).
+ *  Note that the macro arguments assume that the integer being referenced
+ *  is a 32-bit integer (right-justified on the 20) and that bit 0 is the
+ *  most significant bit.
+ */
+
+#ifndef HOSTWDSZ
+#define	HOSTWDSZ	32
+#endif
+
+
+/*###########################  Macros  ######################################*/
+
+/*-------------------------------------------------------------------------
+ * NewDeclareBitField_Reference - Declare a structure similar to the simulator
+ * function "DeclBitfR" except its use is restricted to occur within a larger
+ * enclosing structure or union definition.  This declaration is an unnamed
+ * structure with the argument, name, as the member name and the argument,
+ * uname, as the element name. 
+ *----------------------------------------------------------------------- */
+#define Bitfield_extract(start, length, object) 	\
+    ((object) >> (HOSTWDSZ - (start) - (length)) & 	\
+    ((unsigned)-1 >> (HOSTWDSZ - (length))))
+
+#define Bitfield_signed_extract(start, length, object) \
+    ((int)((object) << start) >> (HOSTWDSZ - (length)))
+
+#define Bitfield_mask(start, len, object)		\
+    ((object) & (((unsigned)-1 >> (HOSTWDSZ-len)) << (HOSTWDSZ-start-len)))
+
+#define Bitfield_deposit(value,start,len,object)  object = \
+    ((object) & ~(((unsigned)-1 >> (HOSTWDSZ-len)) << (HOSTWDSZ-start-len))) | \
+    (((value) & ((unsigned)-1 >> (HOSTWDSZ-len))) << (HOSTWDSZ-start-len))