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Probes fixes for v7.1

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- fprobe: Fixed several bugs, which includes followings:
   . Prevention of re-registration: Added an earlier check to reject
    re-registering an already active fprobe before its state is modified
    during the initialization phase.
   . Robustness in failure paths:
    - Ensured fprobes are correctly removed from all internal tables and
     properly RCU-freed during registration failure.
    - Modified unregister_fprobe() to proceed with unregistration even if
     temporary memory allocation fails.
   . RCU safety in module unloading: Avoided a potential "sleep in RCU"
    warning by removing a kcalloc() call in the module notifier path. This
    also tries to remove fprobe_hash_node even if memory allocation fails.
   . Type-aware unregistration: Fixed a bug where unregistering an fprobe
    did not account for different types (entry-only vs. entry-exit) at the
    same address, which previously left "junk" entries in the underlying
    ftrace/fgraph ops.
   . Unregistration of empty ftrace_ops: Avoided unneeded performance
    overhead because of making registered ftrace_ops empty (means trace
    all functions.) This counts remaining entries and unregister ftrace_ops
    when it becomes empty.
 
  - ftracetest: In addition to the fix, two new selftests to check above
    fixes, are included:
    . Module Unloading Test: Specifically verifies that fprobe events on
     a module are correctly cleaned up and do not trigger "trace-all"
     behavior when the module is removed.
    . Multiple Fprobe Events Test: Ensures that having multiple fprobes on
     the same function correctly manages the ftrace hash map during
     removal.
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Merge tag 'probes-v7.1-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace

Pull probes fixes from Masami Hiramatsu:
 "fprobe bug fixes:

   - Prevent re-registration

     Add an earlier check to reject re-registering an already active
     fprobe before its state is modified during the initialization phase

   - Robustness in failure paths:
      - Ensure fprobes are correctly removed from all internal tables
        and properly RCU-freed during registration failure
      - Make unregister_fprobe() proceed with unregistration even if
        temporary memory allocation fails

   - RCU safety in module unloading

     Avoid a potential "sleep in RCU" warning by removing a kcalloc()
     call in the module notifier path. This also tries to remove
     fprobe_hash_node even if memory allocation fails.

   - Type-aware unregistration

     Fix a bug where unregistering an fprobe did not account for
     different types (entry-only vs entry-exit) at the same address,
     which previously left "junk" entries in the underlying
     ftrace/fgraph ops

   - Unregistration of empty ftrace_ops

     Avoid unneeded performance overhead due to making registered
     ftrace_ops empty - which means 'trace all functions'. This counts
     remaining entries and unregister ftrace_ops when it becomes empty.

  Two new selftests to check above fixes:

   - Module Unloading Test:

     Specifically verifies that fprobe events on a module are correctly
     cleaned up and do not trigger 'trace-all' behavior when the module
     is removed.

   - Multiple Fprobe Events Test:

     Ensure that having multiple fprobes on the same function correctly
     manages the ftrace hash map during removal"

* tag 'probes-v7.1-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace:
  selftests/ftrace: Add a testcase for multiple fprobe events
  selftests/ftrace: Add a testcase for fprobe events on module
  tracing/fprobe: Fix to unregister ftrace_ops if it is empty on module unloading
  tracing/fprobe: Check the same type fprobe on table as the unregistered one
  tracing/fprobe: Avoid kcalloc() in rcu_read_lock section
  tracing/fprobe: Remove fprobe from hash in failure path
  tracing/fprobe: Unregister fprobe even if memory allocation fails
  tracing/fprobe: Reject registration of a registered fprobe before init
This commit is contained in:
Linus Torvalds 2026-04-21 19:05:09 -07:00
commit beaba8bfbb
3 changed files with 466 additions and 162 deletions
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