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, 292 insertions, 0 deletions

diff --git a/drivers/tty/vt/cp437.uni b/drivers/tty/vt/cp437.uni
new file mode 100644
index 000000000..a1991904c
--- /dev/null
+++ b/drivers/tty/vt/cp437.uni
@@ -0,0 +1,292 @@
+# SPDX-License-Identifier: GPL-2.0
+#
+# Unicode table for IBM Codepage 437.  Note that there are many more
+# substitutions that could be conceived (for example, thick-line
+# graphs probably should be replaced with double-line ones, accented
+# Latin characters should replaced with their nonaccented versions,
+# and some upper case Greek characters could be replaced by Latin), however,
+# I have limited myself to the Unicodes used by the kernel ISO 8859-1,
+# DEC VT, and IBM CP 437 tables.
+#
+# --------------------------------
+#
+# Basic IBM dingbats, some of which will never have a purpose clear
+# to mankind
+#
+0x00	U+0000
+0x01	U+263a
+0x02	U+263b
+0x03	U+2665
+0x04	U+2666 U+25c6
+0x05	U+2663
+0x06	U+2660
+0x07	U+2022
+0x08	U+25d8
+0x09	U+25cb
+0x0a	U+25d9
+0x0b	U+2642
+0x0c	U+2640
+0x0d	U+266a
+0x0e	U+266b
+0x0f	U+263c U+00a4
+0x10	U+25b6 U+25ba
+0x11	U+25c0 U+25c4
+0x12	U+2195
+0x13	U+203c
+0x14	U+00b6
+0x15	U+00a7
+0x16	U+25ac
+0x17	U+21a8
+0x18	U+2191
+0x19	U+2193
+0x1a	U+2192
+0x1b	U+2190
+0x1c	U+221f
+0x1d	U+2194
+0x1e	U+25b2
+0x1f	U+25bc
+#
+# The ASCII range is identity-mapped, but some of the characters also
+# have to act as substitutes, especially the upper-case characters.
+#
+0x20	U+0020
+0x21	U+0021
+0x22	U+0022 U+00a8
+0x23	U+0023
+0x24	U+0024
+0x25	U+0025
+0x26	U+0026
+0x27	U+0027 U+00b4
+0x28	U+0028
+0x29	U+0029
+0x2a	U+002a
+0x2b	U+002b
+0x2c	U+002c U+00b8
+0x2d	U+002d U+00ad
+0x2e	U+002e
+0x2f	U+002f
+0x30	U+0030
+0x31	U+0031
+0x32	U+0032
+0x33	U+0033
+0x34	U+0034
+0x35	U+0035
+0x36	U+0036
+0x37	U+0037
+0x38	U+0038
+0x39	U+0039
+0x3a	U+003a
+0x3b	U+003b
+0x3c	U+003c
+0x3d	U+003d
+0x3e	U+003e
+0x3f	U+003f
+0x40	U+0040
+0x41	U+0041 U+00c0 U+00c1 U+00c2 U+00c3
+0x42	U+0042
+0x43	U+0043 U+00a9
+0x44	U+0044 U+00d0
+0x45	U+0045 U+00c8 U+00ca U+00cb
+0x46	U+0046
+0x47	U+0047
+0x48	U+0048
+0x49	U+0049 U+00cc U+00cd U+00ce U+00cf
+0x4a	U+004a
+0x4b	U+004b U+212a
+0x4c	U+004c
+0x4d	U+004d
+0x4e	U+004e
+0x4f	U+004f U+00d2 U+00d3 U+00d4 U+00d5
+0x50	U+0050
+0x51	U+0051
+0x52	U+0052 U+00ae
+0x53	U+0053
+0x54	U+0054
+0x55	U+0055 U+00d9 U+00da U+00db
+0x56	U+0056
+0x57	U+0057
+0x58	U+0058
+0x59	U+0059 U+00dd
+0x5a	U+005a
+0x5b	U+005b
+0x5c	U+005c
+0x5d	U+005d
+0x5e	U+005e
+0x5f	U+005f U+23bd U+f804
+0x60	U+0060
+0x61	U+0061 U+00e3
+0x62	U+0062
+0x63	U+0063
+0x64	U+0064
+0x65	U+0065
+0x66	U+0066
+0x67	U+0067
+0x68	U+0068
+0x69	U+0069
+0x6a	U+006a
+0x6b	U+006b
+0x6c	U+006c
+0x6d	U+006d
+0x6e	U+006e
+0x6f	U+006f U+00f5
+0x70	U+0070
+0x71	U+0071
+0x72	U+0072
+0x73	U+0073
+0x74	U+0074
+0x75	U+0075
+0x76	U+0076
+0x77	U+0077
+0x78	U+0078 U+00d7
+0x79	U+0079 U+00fd
+0x7a	U+007a
+0x7b	U+007b
+0x7c	U+007c U+00a6
+0x7d	U+007d
+0x7e	U+007e
+#
+# Okay, what on Earth is this one supposed to be used for?
+#
+0x7f	U+2302
+#
+# Non-English characters, mostly lower case letters...
+#
+0x80	U+00c7
+0x81	U+00fc
+0x82	U+00e9
+0x83	U+00e2
+0x84	U+00e4
+0x85	U+00e0
+0x86	U+00e5
+0x87	U+00e7
+0x88	U+00ea
+0x89	U+00eb
+0x8a	U+00e8
+0x8b	U+00ef
+0x8c	U+00ee
+0x8d	U+00ec
+0x8e	U+00c4
+0x8f	U+00c5 U+212b
+0x90	U+00c9
+0x91	U+00e6
+0x92	U+00c6
+0x93	U+00f4
+0x94	U+00f6
+0x95	U+00f2
+0x96	U+00fb
+0x97	U+00f9
+0x98	U+00ff
+0x99	U+00d6
+0x9a	U+00dc
+0x9b	U+00a2
+0x9c	U+00a3
+0x9d	U+00a5
+0x9e	U+20a7
+0x9f	U+0192
+0xa0	U+00e1
+0xa1	U+00ed
+0xa2	U+00f3
+0xa3	U+00fa
+0xa4	U+00f1
+0xa5	U+00d1
+0xa6	U+00aa
+0xa7	U+00ba
+0xa8	U+00bf
+0xa9	U+2310
+0xaa	U+00ac
+0xab	U+00bd
+0xac	U+00bc
+0xad	U+00a1
+0xae	U+00ab
+0xaf	U+00bb
+#
+# Block graphics
+#
+0xb0	U+2591
+0xb1	U+2592
+0xb2	U+2593
+0xb3	U+2502
+0xb4	U+2524
+0xb5	U+2561
+0xb6	U+2562
+0xb7	U+2556
+0xb8	U+2555
+0xb9	U+2563
+0xba	U+2551
+0xbb	U+2557
+0xbc	U+255d
+0xbd	U+255c
+0xbe	U+255b
+0xbf	U+2510
+0xc0	U+2514
+0xc1	U+2534
+0xc2	U+252c
+0xc3	U+251c
+0xc4	U+2500
+0xc5	U+253c
+0xc6	U+255e
+0xc7	U+255f
+0xc8	U+255a
+0xc9	U+2554
+0xca	U+2569
+0xcb	U+2566
+0xcc	U+2560
+0xcd	U+2550
+0xce	U+256c
+0xcf	U+2567
+0xd0	U+2568
+0xd1	U+2564
+0xd2	U+2565
+0xd3	U+2559
+0xd4	U+2558
+0xd5	U+2552
+0xd6	U+2553
+0xd7	U+256b
+0xd8	U+256a
+0xd9	U+2518
+0xda	U+250c
+0xdb	U+2588
+0xdc	U+2584
+0xdd	U+258c
+0xde	U+2590
+0xdf	U+2580
+#
+# Greek letters and mathematical symbols
+#
+0xe0	U+03b1
+0xe1	U+03b2 U+00df
+0xe2	U+0393
+0xe3	U+03c0
+0xe4	U+03a3
+0xe5	U+03c3
+0xe6	U+00b5 U+03bc
+0xe7	U+03c4
+0xe8	U+03a6 U+00d8
+0xe9	U+0398
+0xea	U+03a9 U+2126
+0xeb	U+03b4 U+00f0
+0xec	U+221e
+0xed	U+03c6 U+00f8
+0xee	U+03b5 U+2208
+0xef	U+2229
+0xf0	U+2261
+0xf1	U+00b1
+0xf2	U+2265
+0xf3	U+2264
+0xf4	U+2320
+0xf5	U+2321
+0xf6	U+00f7
+0xf7	U+2248
+0xf8	U+00b0
+0xf9	U+2219
+0xfa	U+00b7
+0xfb	U+221a
+0xfc	U+207f
+0xfd	U+00b2
+#
+# Square bullet, non-spacing blank
+# Mapping U+fffd to the square bullet means it is the substitution
+# character
+# 
+0xfe	U+25a0 U+fffd
+0xff	U+00a0