6.12-stable review patch. If anyone has any objections, please let me know.
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From: Masami Hiramatsu (Google) mhiramat@kernel.org
commit ac91052f0ae5be9e46211ba92cc31c0e3b0a933a upstream.
When enabling the tracepoint at loading module, the target module refcount is incremented by find_tracepoint_in_module(). But it is unnecessary because the module is not unloaded while processing module loading callbacks. Moreover, the refcount is not decremented in that function. To be clear the module refcount handling, move the try_module_get() callsite to trace_fprobe_create_internal(), where it is actually required.
Link: https://lore.kernel.org/all/174182761071.83274.18334217580449925882.stgit@de...
Fixes: 57a7e6de9e30 ("tracing/fprobe: Support raw tracepoints on future loaded modules") Signed-off-by: Masami Hiramatsu (Google) mhiramat@kernel.org Cc: stable@vger.kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- kernel/trace/trace_fprobe.c | 21 ++++++++------------- 1 file changed, 8 insertions(+), 13 deletions(-)
--- a/kernel/trace/trace_fprobe.c +++ b/kernel/trace/trace_fprobe.c @@ -889,13 +889,8 @@ static void __find_tracepoint_module_cb(
if (!data->tpoint && !strcmp(data->tp_name, tp->name)) { data->tpoint = tp; - if (!data->mod) { + if (!data->mod) data->mod = mod; - if (!try_module_get(data->mod)) { - data->tpoint = NULL; - data->mod = NULL; - } - } } }
@@ -907,13 +902,7 @@ static void __find_tracepoint_cb(struct data->tpoint = tp; }
-/* - * Find a tracepoint from kernel and module. If the tracepoint is in a module, - * this increments the module refcount to prevent unloading until the - * trace_fprobe is registered to the list. After registering the trace_fprobe - * on the trace_fprobe list, the module refcount is decremented because - * tracepoint_probe_module_cb will handle it. - */ +/* Find a tracepoint from kernel and module. */ static struct tracepoint *find_tracepoint(const char *tp_name, struct module **tp_mod) { @@ -942,6 +931,7 @@ static void reenable_trace_fprobe(struct } }
+/* Find a tracepoint from specified module. */ static struct tracepoint *find_tracepoint_in_module(struct module *mod, const char *tp_name) { @@ -1177,6 +1167,11 @@ static int __trace_fprobe_create(int arg if (is_tracepoint) { ctx.flags |= TPARG_FL_TPOINT; tpoint = find_tracepoint(symbol, &tp_mod); + /* lock module until register this tprobe. */ + if (tp_mod && !try_module_get(tp_mod)) { + tpoint = NULL; + tp_mod = NULL; + } if (tpoint) { ctx.funcname = kallsyms_lookup( (unsigned long)tpoint->probestub,