[PATCH v3 0/5] kprobes: Fixes for ftrace ops and optprobe state machine

["Masami Hiramatsu (Google)" <mhiramat@kernel.org>]

Hi,

Here is v3 of the remaining bug fixes for kprobes and optprobes.
The previous version is here:

  https://lore.kernel.org/all/179427358690.291326.2078291446658598883.stgit@devnote2/

This version restores __arm_kprobe() fix as patch 3, and update the KUnit
test code to check it.
This includes following fixes.

1. Ftrace Ops Switching for Post-Handlers (Patch 1):
   - When adding a second probe with a post_handler to an existing ftrace
     kprobe, the aggregate probe's post_handler was set but remained armed
     on kprobe_ftrace_ops. Subsequent disarming attempted to disarm from
     kprobe_ipmodify_ops, failing with -ENOENT and leaking the armed probe.
     Switch ftrace ops safely in register_aggr_kprobe() outside of
     text_mutex and cpus_read_lock.

2. Optprobe State Machine & Tasks RCU Quiescence (Patches 2-4):
   - Forcibly unoptimized probes (unoptimize_kprobe(force = true)) were
     not queued to cooling_list, causing kprobe_disarmed() to return true
     prematurely and risking use-after-free in the optinsn detour buffer
     before Tasks RCU completed.
   - When re-arming a probe that is queued on unoptimizing_list before the
     optimizer thread runs, skip arch_arm_kprobe() in __arm_kprobe() so
     the active jump instruction is not overwritten with a breakpoint.
   - When a disabled cooling probe finishes cooling and transitions to
     safely disarmed in optprobe_finalize_generation(), re-optimize any
     blocked sibling probe whose jump range covers its address.

3. KUnit Regression Tests (Patch 5):
   - Add KUnit test cases to lib/tests/test_kprobes.c covering the recent
     kprobes, kretprobes, ftrace ops, and optprobe fixes.

Changes in v3:
[03/05]
 - Restore the __arm_kprobe() fix that was accidentally dropped in v2
   while omitting the reuse_unused_kprobe() hunk superseded by commit
   1ffd6efb1b58 ("kprobes: Arm reused optprobe on cooling list").
[05/05]
 - Check that the jump opcode at *opt_kp.addr is preserved across
   disable_kprobe() and enable_kprobe() in
   test_optprobe_rearm_unoptimizing().

Thank you,

---
base-commit: 1ffd6efb1b58e596ed70f660182803264a4c84d9

Masami Hiramatsu (Google) (5):
      kprobes: Switch ftrace ops when adding probe with post_handler
      kprobes: Fix UAF and queue cooling probes on forced unoptimization
      kprobes: Do not overwrite jump instruction when re-arming unoptimizing probe
      kprobes: Re-optimize blocked sibling probe when cooling finishes
      kprobes: Add KUnit test cases for kprobes regressions


 kernel/kprobes.c         |  116 +++++++++++++++++++++++++++-----------
 lib/tests/test_kprobes.c |  139 ++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 220 insertions(+), 35 deletions(-)

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