linux-kernel - [RFC PATCH 0/2] x86: kprobes: Fix CFI

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Date:   Mon, 10 Jul 2023 21:14:13 +0900
From:   "Masami Hiramatsu (Google)" <mhiramat@...nel.org>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Petr Pavlu <petr.pavlu@...e.com>, tglx@...utronix.de,
        mingo@...hat.com, bp@...en8.de, dave.hansen@...ux.intel.com,
        hpa@...or.com, samitolvanen@...gle.com, x86@...nel.org,
        linux-trace-kernel@...r.kernel.org, linux-kernel@...r.kernel.org,
        Masami Hiramatsu <mhiramat@...nel.org>
Subject: [RFC PATCH 0/2] x86: kprobes: Fix CFI_CLANG related issues

Hi Peter,

Here I tried to fix 2 issues discussed on the previous thread;

https://lore.kernel.org/all/20230706113403.GI2833176@hirez.programming.kicks-ass.net/

- Prohibit probing on __cfi_* preamble symbols, which have the typeid.
- Prohibit probing on compiler generated movl/addl which is used for
  detecting typeid on x86.

I'm not sure how arm64 implemented, but it seems 
cfi_handler()@arch/arm64/kernel/traps.c just reads the registers for 
the typeid instead of decoding the instructions.

I just build tested, since I could not boot the kernel with CFI_CLANG=y.
Would anyone know something about this error?

[    0.141030] MMIO Stale Data: Unknown: No mitigations
[    0.153511] SMP alternatives: Using kCFI
[    0.164593] Freeing SMP alternatives memory: 36K
[    0.165053] Kernel panic - not syncing: stack-protector: Kernel stack is corrupted in: start_kernel+0x472/0x48b
[    0.166028] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 6.4.2-00002-g12b1b2fca8ef #126
[    0.166028] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-1ubuntu1.1 04/01/2014
[    0.166028] Call Trace:
[    0.166028]  <TASK>
[    0.166028]  dump_stack_lvl+0x6e/0xb0
[    0.166028]  panic+0x146/0x2f0
[    0.166028]  ? start_kernel+0x472/0x48b
[    0.166028]  __stack_chk_fail+0x14/0x20
[    0.166028]  start_kernel+0x472/0x48b
[    0.166028]  x86_64_start_reservations+0x24/0x30
[    0.166028]  x86_64_start_kernel+0xa6/0xbb
[    0.166028]  secondary_startup_64_no_verify+0x106/0x11b
[    0.166028]  </TASK>
[    0.166028] ---[ end Kernel panic - not syncing: stack-protector: Kernel stack is corrupted in: start_kernel+0x472/0x48b ]---


Thank you,

---

Masami Hiramatsu (Google) (2):
      kprobes: Prohibit probing on CFI preamble symbol
      x86/kprobes: Prohibit probing on compiler generated CFI checking code


 arch/x86/kernel/kprobes/core.c |   34 ++++++++++++++++++++++++++++++++++
 kernel/kprobes.c               |   17 ++++++++++++++++-
 2 files changed, 50 insertions(+), 1 deletion(-)

--
Masami Hiramatsu (Google) <mhiramat@...nel.org>