fprobe: Release rethook after the ftrace_ops is unregistered

While running bpf selftests it's possible to get following fault:

  general protection fault, probably for non-canonical address \
  0x6b6b6b6b6b6b6b6b: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC NOPTI
  ...
  Call Trace:
   <TASK>
   fprobe_handler+0xc1/0x270
   ? __pfx_bpf_testmod_init+0x10/0x10
   ? __pfx_bpf_testmod_init+0x10/0x10
   ? bpf_fentry_test1+0x5/0x10
   ? bpf_fentry_test1+0x5/0x10
   ? bpf_testmod_init+0x22/0x80
   ? do_one_initcall+0x63/0x2e0
   ? rcu_is_watching+0xd/0x40
   ? kmalloc_trace+0xaf/0xc0
   ? do_init_module+0x60/0x250
   ? __do_sys_finit_module+0xac/0x120
   ? do_syscall_64+0x37/0x90
   ? entry_SYSCALL_64_after_hwframe+0x72/0xdc
   </TASK>

In unregister_fprobe function we can't release fp->rethook while it's
possible there are some of its users still running on another cpu.

Moving rethook_free call after fp->ops is unregistered with
unregister_ftrace_function call.

Link: https://lore.kernel.org/all/20230615115236.3476617-1-jolsa@kernel.org/
Fixes: 5b0ab78998e3 ("fprobe: Add exit_handler support")
Cc: stable@vger.kernel.org
Reviewed-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>

diff --git a/kernel/trace/fprobe.c b/kernel/trace/fprobe.c
index 18d36842faf575d2057439aa22f5b8b4064858af..0121e8c0d54e742256d6ba1d7a3f066a8291be46 100644 (file)
--- a/kernel/trace/fprobe.c
+++ b/kernel/trace/fprobe.c
@@ -364,19 +364,13 @@ int unregister_fprobe(struct fprobe *fp)
                    fp->ops.saved_func != fprobe_kprobe_handler))
                return -EINVAL;
 
-       /*
-        * rethook_free() starts disabling the rethook, but the rethook handlers
-        * may be running on other processors at this point. To make sure that all
-        * current running handlers are finished, call unregister_ftrace_function()
-        * after this.
-        */
-       if (fp->rethook)
-               rethook_free(fp->rethook);
-
        ret = unregister_ftrace_function(&fp->ops);
        if (ret < 0)
                return ret;
 
+       if (fp->rethook)
+               rethook_free(fp->rethook);
+
        ftrace_free_filter(&fp->ops);
 
        return ret;