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Message-Id: <172398528350.293426.8347220120333730248.stgit@devnote2>
Date: Sun, 18 Aug 2024 21:48:03 +0900
From: "Masami Hiramatsu (Google)" <mhiramat@...nel.org>
To: Alexei Starovoitov <alexei.starovoitov@...il.com>,
Steven Rostedt <rostedt@...dmis.org>,
Florent Revest <revest@...omium.org>
Cc: linux-trace-kernel@...r.kernel.org,
LKML <linux-kernel@...r.kernel.org>,
Martin KaFai Lau <martin.lau@...ux.dev>,
bpf <bpf@...r.kernel.org>,
Sven Schnelle <svens@...ux.ibm.com>,
Alexei Starovoitov <ast@...nel.org>,
Jiri Olsa <jolsa@...nel.org>,
Arnaldo Carvalho de Melo <acme@...nel.org>,
Daniel Borkmann <daniel@...earbox.net>,
Alan Maguire <alan.maguire@...cle.com>,
Mark Rutland <mark.rutland@....com>,
Peter Zijlstra <peterz@...radead.org>,
Thomas Gleixner <tglx@...utronix.de>,
Guo Ren <guoren@...nel.org>
Subject: [PATCH v13 01/20] tracing: fgraph: Fix to add new fgraph_ops to array after ftrace_startup_subops()
From: Masami Hiramatsu (Google) <mhiramat@...nel.org>
Since the register_ftrace_graph() assigns a new fgraph_ops to
fgraph_array before registring it by ftrace_startup_subops(), the new
fgraph_ops can be used in function_graph_enter().
In most cases, it is still OK because those fgraph_ops's hashtable is
already initialized by ftrace_set_filter*() etc.
But if a user registers a new fgraph_ops which does not initialize the
hash list, ftrace_ops_test() in function_graph_enter() causes a NULL
pointer dereference BUG because fgraph_ops->ops.func_hash is NULL.
This can be reproduced by the below commands because function profiler's
fgraph_ops does not initialize the hash list;
# cd /sys/kernel/tracing
# echo function_graph > current_tracer
# echo 1 > function_profile_enabled
To fix this problem, add a new fgraph_ops to fgraph_array after
ftrace_startup_subops(). Thus, until the new fgraph_ops is initialized,
we will see fgraph_stub on the corresponding fgraph_array entry.
Fixes: c132be2c4fcc ("function_graph: Have the instances use their own ftrace_ops for filtering")
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@...nel.org>
---
kernel/trace/fgraph.c | 31 ++++++++++++++++++-------------
1 file changed, 18 insertions(+), 13 deletions(-)
diff --git a/kernel/trace/fgraph.c b/kernel/trace/fgraph.c
index d1d5ea2d0a1b..d7d4fb403f6f 100644
--- a/kernel/trace/fgraph.c
+++ b/kernel/trace/fgraph.c
@@ -1206,18 +1206,24 @@ static void init_task_vars(int idx)
read_unlock(&tasklist_lock);
}
-static void ftrace_graph_enable_direct(bool enable_branch)
+static void ftrace_graph_enable_direct(bool enable_branch, struct fgraph_ops *gops)
{
trace_func_graph_ent_t func = NULL;
trace_func_graph_ret_t retfunc = NULL;
int i;
- for_each_set_bit(i, &fgraph_array_bitmask,
- sizeof(fgraph_array_bitmask) * BITS_PER_BYTE) {
- func = fgraph_array[i]->entryfunc;
- retfunc = fgraph_array[i]->retfunc;
- fgraph_direct_gops = fgraph_array[i];
- }
+ if (gops) {
+ func = gops->entryfunc;
+ retfunc = gops->retfunc;
+ fgraph_direct_gops = gops;
+ } else {
+ for_each_set_bit(i, &fgraph_array_bitmask,
+ sizeof(fgraph_array_bitmask) * BITS_PER_BYTE) {
+ func = fgraph_array[i]->entryfunc;
+ retfunc = fgraph_array[i]->retfunc;
+ fgraph_direct_gops = fgraph_array[i];
+ }
+ }
if (WARN_ON_ONCE(!func))
return;
@@ -1256,8 +1262,6 @@ int register_ftrace_graph(struct fgraph_ops *gops)
ret = -ENOSPC;
goto out;
}
-
- fgraph_array[i] = gops;
gops->idx = i;
ftrace_graph_active++;
@@ -1266,7 +1270,7 @@ int register_ftrace_graph(struct fgraph_ops *gops)
ftrace_graph_disable_direct(true);
if (ftrace_graph_active == 1) {
- ftrace_graph_enable_direct(false);
+ ftrace_graph_enable_direct(false, gops);
register_pm_notifier(&ftrace_suspend_notifier);
ret = start_graph_tracing();
if (ret)
@@ -1281,14 +1285,15 @@ int register_ftrace_graph(struct fgraph_ops *gops)
} else {
init_task_vars(gops->idx);
}
-
/* Always save the function, and reset at unregistering */
gops->saved_func = gops->entryfunc;
ret = ftrace_startup_subops(&graph_ops, &gops->ops, command);
+ if (!ret)
+ fgraph_array[i] = gops;
+
error:
if (ret) {
- fgraph_array[i] = &fgraph_stub;
ftrace_graph_active--;
gops->saved_func = NULL;
fgraph_lru_release_index(i);
@@ -1324,7 +1329,7 @@ void unregister_ftrace_graph(struct fgraph_ops *gops)
ftrace_shutdown_subops(&graph_ops, &gops->ops, command);
if (ftrace_graph_active == 1)
- ftrace_graph_enable_direct(true);
+ ftrace_graph_enable_direct(true, NULL);
else if (!ftrace_graph_active)
ftrace_graph_disable_direct(false);
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