ftrace: Fix regression with module command in stack_trace_filter

When doing the following command:

 # echo ":mod:kvm_intel" > /sys/kernel/tracing/stack_trace_filter

it triggered a crash.

This happened with the clean up of probes. It required all callers to the
regex function (doing ftrace filtering) to have ops->private be a pointer to
a trace_array. But for the stack tracer, that is not the case.

Allow for the ops->private to be NULL, and change the function command
callbacks to handle the trace_array pointer being NULL as well.

Fixes: d2afd57a4b96 ("tracing/ftrace: Allow instances to have their own function probes")
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

1 files changed, 12 insertions, 0 deletions

diff --git a/kernel/trace/trace_functions.c b/kernel/trace/trace_functions.c
index a3bddbfd0874..a0910c0cdf2e 100644
--- a/kernel/trace/trace_functions.c
+++ b/kernel/trace/trace_functions.c
@@ -654,6 +654,9 @@ ftrace_trace_onoff_callback(struct trace_array *tr, struct ftrace_hash *hash,
 {
         struct ftrace_probe_ops *ops;
 
+        if (!tr)
+                return -ENODEV;
+
         /* we register both traceon and traceoff to this callback */
         if (strcmp(cmd, "traceon") == 0)
                 ops = param ? &traceon_count_probe_ops : &traceon_probe_ops;
@@ -670,6 +673,9 @@ ftrace_stacktrace_callback(struct trace_array *tr, struct ftrace_hash *hash,
 {
         struct ftrace_probe_ops *ops;
 
+        if (!tr)
+                return -ENODEV;
+
         ops = param ? &stacktrace_count_probe_ops : &stacktrace_probe_ops;
 
         return ftrace_trace_probe_callback(tr, ops, hash, glob, cmd,
@@ -682,6 +688,9 @@ ftrace_dump_callback(struct trace_array *tr, struct ftrace_hash *hash,
 {
         struct ftrace_probe_ops *ops;
 
+        if (!tr)
+                return -ENODEV;
+
         ops = &dump_probe_ops;
 
         /* Only dump once. */
@@ -695,6 +704,9 @@ ftrace_cpudump_callback(struct trace_array *tr, struct ftrace_hash *hash,
 {
         struct ftrace_probe_ops *ops;
 
+        if (!tr)
+                return -ENODEV;
+
         ops = &cpudump_probe_ops;
 
         /* Only dump once. */