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, 188 insertions, 0 deletions

diff --git a/Documentation/admin-guide/unicode.rst b/Documentation/admin-guide/unicode.rst
new file mode 100644
index 000000000..cba7e5017
--- /dev/null
+++ b/Documentation/admin-guide/unicode.rst
@@ -0,0 +1,188 @@
+Unicode support
+===============
+
+		 Last update: 2005-01-17, version 1.4
+
+Note: The original version of this document, which was maintained at
+lanana.org as part of the Linux Assigned Names And Numbers Authority
+(LANANA) project, is no longer existent.  So, this version in the
+mainline Linux kernel is now the maintained main document.
+
+Introduction
+------------
+
+The Linux kernel code has been rewritten to use Unicode to map
+characters to fonts.  By downloading a single Unicode-to-font table,
+both the eight-bit character sets and UTF-8 mode are changed to use
+the font as indicated.
+
+This changes the semantics of the eight-bit character tables subtly.
+The four character tables are now:
+
+=============== =============================== ================
+Map symbol	Map name			Escape code (G0)
+=============== =============================== ================
+LAT1_MAP	Latin-1 (ISO 8859-1)		ESC ( B
+GRAF_MAP	DEC VT100 pseudographics	ESC ( 0
+IBMPC_MAP	IBM code page 437		ESC ( U
+USER_MAP	User defined			ESC ( K
+=============== =============================== ================
+
+In particular, ESC ( U is no longer "straight to font", since the font
+might be completely different than the IBM character set.  This
+permits for example the use of block graphics even with a Latin-1 font
+loaded.
+
+Note that although these codes are similar to ISO 2022, neither the
+codes nor their uses match ISO 2022; Linux has two 8-bit codes (G0 and
+G1), whereas ISO 2022 has four 7-bit codes (G0-G3).
+
+In accordance with the Unicode standard/ISO 10646 the range U+F000 to
+U+F8FF has been reserved for OS-wide allocation (the Unicode Standard
+refers to this as a "Corporate Zone", since this is inaccurate for
+Linux we call it the "Linux Zone").  U+F000 was picked as the starting
+point since it lets the direct-mapping area start on a large power of
+two (in case 1024- or 2048-character fonts ever become necessary).
+This leaves U+E000 to U+EFFF as End User Zone.
+
+[v1.2]: The Unicodes range from U+F000 and up to U+F7FF have been
+hard-coded to map directly to the loaded font, bypassing the
+translation table.  The user-defined map now defaults to U+F000 to
+U+F0FF, emulating the previous behaviour.  In practice, this range
+might be shorter; for example, vgacon can only handle 256-character
+(U+F000..U+F0FF) or 512-character (U+F000..U+F1FF) fonts.
+
+
+Actual characters assigned in the Linux Zone
+--------------------------------------------
+
+In addition, the following characters not present in Unicode 1.1.4
+have been defined; these are used by the DEC VT graphics map.  [v1.2]
+THIS USE IS OBSOLETE AND SHOULD NO LONGER BE USED; PLEASE SEE BELOW.
+
+====== ======================================
+U+F800 DEC VT GRAPHICS HORIZONTAL LINE SCAN 1
+U+F801 DEC VT GRAPHICS HORIZONTAL LINE SCAN 3
+U+F803 DEC VT GRAPHICS HORIZONTAL LINE SCAN 7
+U+F804 DEC VT GRAPHICS HORIZONTAL LINE SCAN 9
+====== ======================================
+
+The DEC VT220 uses a 6x10 character matrix, and these characters form
+a smooth progression in the DEC VT graphics character set.  I have
+omitted the scan 5 line, since it is also used as a block-graphics
+character, and hence has been coded as U+2500 FORMS LIGHT HORIZONTAL.
+
+[v1.3]: These characters have been officially added to Unicode 3.2.0;
+they are added at U+23BA, U+23BB, U+23BC, U+23BD.  Linux now uses the
+new values.
+
+[v1.2]: The following characters have been added to represent common
+keyboard symbols that are unlikely to ever be added to Unicode proper
+since they are horribly vendor-specific.  This, of course, is an
+excellent example of horrible design.
+
+====== ======================================
+U+F810 KEYBOARD SYMBOL FLYING FLAG
+U+F811 KEYBOARD SYMBOL PULLDOWN MENU
+U+F812 KEYBOARD SYMBOL OPEN APPLE
+U+F813 KEYBOARD SYMBOL SOLID APPLE
+====== ======================================
+
+Klingon language support
+------------------------
+
+In 1996, Linux was the first operating system in the world to add
+support for the artificial language Klingon, created by Marc Okrand
+for the "Star Trek" television series.	This encoding was later
+adopted by the ConScript Unicode Registry and proposed (but ultimately
+rejected) for inclusion in Unicode Plane 1.  Thus, it remains as a
+Linux/CSUR private assignment in the Linux Zone.
+
+This encoding has been endorsed by the Klingon Language Institute.
+For more information, contact them at:
+
+	http://www.kli.org/
+
+Since the characters in the beginning of the Linux CZ have been more
+of the dingbats/symbols/forms type and this is a language, I have
+located it at the end, on a 16-cell boundary in keeping with standard
+Unicode practice.
+
+.. note::
+
+  This range is now officially managed by the ConScript Unicode
+  Registry.  The normative reference is at:
+
+	https://www.evertype.com/standards/csur/klingon.html
+
+Klingon has an alphabet of 26 characters, a positional numeric writing
+system with 10 digits, and is written left-to-right, top-to-bottom.
+
+Several glyph forms for the Klingon alphabet have been proposed.
+However, since the set of symbols appear to be consistent throughout,
+with only the actual shapes being different, in keeping with standard
+Unicode practice these differences are considered font variants.
+
+======	=======================================================
+U+F8D0	KLINGON LETTER A
+U+F8D1	KLINGON LETTER B
+U+F8D2	KLINGON LETTER CH
+U+F8D3	KLINGON LETTER D
+U+F8D4	KLINGON LETTER E
+U+F8D5	KLINGON LETTER GH
+U+F8D6	KLINGON LETTER H
+U+F8D7	KLINGON LETTER I
+U+F8D8	KLINGON LETTER J
+U+F8D9	KLINGON LETTER L
+U+F8DA	KLINGON LETTER M
+U+F8DB	KLINGON LETTER N
+U+F8DC	KLINGON LETTER NG
+U+F8DD	KLINGON LETTER O
+U+F8DE	KLINGON LETTER P
+U+F8DF	KLINGON LETTER Q
+	- Written <q> in standard Okrand Latin transliteration
+U+F8E0	KLINGON LETTER QH
+	- Written <Q> in standard Okrand Latin transliteration
+U+F8E1	KLINGON LETTER R
+U+F8E2	KLINGON LETTER S
+U+F8E3	KLINGON LETTER T
+U+F8E4	KLINGON LETTER TLH
+U+F8E5	KLINGON LETTER U
+U+F8E6	KLINGON LETTER V
+U+F8E7	KLINGON LETTER W
+U+F8E8	KLINGON LETTER Y
+U+F8E9	KLINGON LETTER GLOTTAL STOP
+
+U+F8F0	KLINGON DIGIT ZERO
+U+F8F1	KLINGON DIGIT ONE
+U+F8F2	KLINGON DIGIT TWO
+U+F8F3	KLINGON DIGIT THREE
+U+F8F4	KLINGON DIGIT FOUR
+U+F8F5	KLINGON DIGIT FIVE
+U+F8F6	KLINGON DIGIT SIX
+U+F8F7	KLINGON DIGIT SEVEN
+U+F8F8	KLINGON DIGIT EIGHT
+U+F8F9	KLINGON DIGIT NINE
+
+U+F8FD	KLINGON COMMA
+U+F8FE	KLINGON FULL STOP
+U+F8FF	KLINGON SYMBOL FOR EMPIRE
+======	=======================================================
+
+Other Fictional and Artificial Scripts
+--------------------------------------
+
+Since the assignment of the Klingon Linux Unicode block, a registry of
+fictional and artificial scripts has been established by John Cowan
+<jcowan@reutershealth.com> and Michael Everson <everson@evertype.com>.
+The ConScript Unicode Registry is accessible at:
+
+	  https://www.evertype.com/standards/csur/
+
+The ranges used fall at the low end of the End User Zone and can hence
+not be normatively assigned, but it is recommended that people who
+wish to encode fictional scripts use these codes, in the interest of
+interoperability.  For Klingon, CSUR has adopted the Linux encoding.
+The CSUR people are driving adding Tengwar and Cirth into Unicode
+Plane 1; the addition of Klingon to Unicode Plane 1 has been rejected
+and so the above encoding remains official.