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, 41 insertions, 0 deletions

diff --git a/fs/isofs/Kconfig b/fs/isofs/Kconfig
new file mode 100644
index 000000000..51434f2a4
--- /dev/null
+++ b/fs/isofs/Kconfig
@@ -0,0 +1,41 @@
+# SPDX-License-Identifier: GPL-2.0-only
+config ISO9660_FS
+	tristate "ISO 9660 CDROM file system support"
+	select BUFFER_HEAD
+	help
+	  This is the standard file system used on CD-ROMs.  It was previously
+	  known as "High Sierra File System" and is called "hsfs" on other
+	  Unix systems.  The so-called Rock-Ridge extensions which allow for
+	  long Unix filenames and symbolic links are also supported by this
+	  driver.  If you have a CD-ROM drive and want to do more with it than
+	  just listen to audio CDs and watch its LEDs, say Y (and read
+	  <file:Documentation/filesystems/isofs.rst> and the CD-ROM-HOWTO,
+	  available from <http://www.tldp.org/docs.html#howto>), thereby
+	  enlarging your kernel by about 27 KB; otherwise say N.
+
+	  To compile this file system support as a module, choose M here: the
+	  module will be called isofs.
+
+config JOLIET
+	bool "Microsoft Joliet CDROM extensions"
+	depends on ISO9660_FS
+	select NLS
+	help
+	  Joliet is a Microsoft extension for the ISO 9660 CD-ROM file system
+	  which allows for long filenames in unicode format (unicode is the
+	  new 16 bit character code, successor to ASCII, which encodes the
+	  characters of almost all languages of the world; see
+	  <http://www.unicode.org/> for more information).  Say Y here if you
+	  want to be able to read Joliet CD-ROMs under Linux.
+
+config ZISOFS
+	bool "Transparent decompression extension"
+	depends on ISO9660_FS
+	select ZLIB_INFLATE
+	help
+	  This is a Linux-specific extension to RockRidge which lets you store
+	  data in compressed form on a CD-ROM and have it transparently
+	  decompressed when the CD-ROM is accessed.  See
+	  <http://www.kernel.org/pub/linux/utils/fs/zisofs/> for the tools
+	  necessary to create such a filesystem.  Say Y here if you want to be
+	  able to read such compressed CD-ROMs.