tracing: Add tracing_check_open_get_tr()

Currently, most files in the tracefs directory test if tracing_disabled is
set. If so, it should return -ENODEV. The tracing_disabled is called when
tracing is found to be broken. Originally it was done in case the ring
buffer was found to be corrupted, and we wanted to prevent reading it from
crashing the kernel. But it's also called if a tracing selftest fails on
boot. It's a one way switch. That is, once it is triggered, tracing is
disabled until reboot.

As most tracefs files can also be used by instances in the tracefs
directory, they need to be carefully done. Each instance has a trace_array
associated to it, and when the instance is removed, the trace_array is
freed. But if an instance is opened with a reference to the trace_array,
then it requires looking up the trace_array to get its ref counter (as there
could be a race with it being deleted and the open itself). Once it is
found, a reference is added to prevent the instance from being removed (and
the trace_array associated with it freed).

Combine the two checks (tracing_disabled and trace_array_get()) into a
single helper function. This will also make it easier to add lockdown to
tracefs later.

Link: http://lkml.kernel.org/r/20191011135458.7399da44@gandalf.local.home
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 32c2eb167de0d6718f67a54ade450407c67cf367..8b765a55e01cfcd415a2b50ad603319f1736bc71 100644 (file)
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -3547,7 +3547,7 @@ ftrace_regex_open(struct ftrace_ops *ops, int flag,
        if (unlikely(ftrace_disabled))
                return -ENODEV;
 
-       if (tr && trace_array_get(tr) < 0)
+       if (tracing_check_open_get_tr(tr))
                return -ENODEV;
 
        iter = kzalloc(sizeof(*iter), GFP_KERNEL);
@@ -6546,8 +6546,9 @@ ftrace_pid_open(struct inode *inode, struct file *file)
        struct seq_file *m;
        int ret = 0;
 
-       if (trace_array_get(tr) < 0)
-               return -ENODEV;
+       ret = tracing_check_open_get_tr(tr);
+       if (ret)
+               return ret;
 
        if ((file->f_mode & FMODE_WRITE) &&
            (file->f_flags & O_TRUNC))

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 94f1b91249398e03ee1ceb3b74fa76e487e1fad7..26ee280f852b17e0b8890b64e51afdc683249853 100644 (file)
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -304,6 +304,17 @@ void trace_array_put(struct trace_array *this_tr)
        mutex_unlock(&trace_types_lock);
 }
 
+int tracing_check_open_get_tr(struct trace_array *tr)
+{
+       if (tracing_disabled)
+               return -ENODEV;
+
+       if (tr && trace_array_get(tr) < 0)
+               return -ENODEV;
+
+       return 0;
+}
+
 int call_filter_check_discard(struct trace_event_call *call, void *rec,
                              struct ring_buffer *buffer,
                              struct ring_buffer_event *event)
@@ -4140,8 +4151,11 @@ release:
 
 int tracing_open_generic(struct inode *inode, struct file *filp)
 {
-       if (tracing_disabled)
-               return -ENODEV;
+       int ret;
+
+       ret = tracing_check_open_get_tr(NULL);
+       if (ret)
+               return ret;
 
        filp->private_data = inode->i_private;
        return 0;
@@ -4159,12 +4173,11 @@ bool tracing_is_disabled(void)
 int tracing_open_generic_tr(struct inode *inode, struct file *filp)
 {
        struct trace_array *tr = inode->i_private;
+       int ret;
 
-       if (tracing_disabled)
-               return -ENODEV;
-
-       if (trace_array_get(tr) < 0)
-               return -ENODEV;
+       ret = tracing_check_open_get_tr(tr);
+       if (ret)
+               return ret;
 
        filp->private_data = inode->i_private;
 
@@ -4233,10 +4246,11 @@ static int tracing_open(struct inode *inode, struct file *file)
 {
        struct trace_array *tr = inode->i_private;
        struct trace_iterator *iter;
-       int ret = 0;
+       int ret;
 
-       if (trace_array_get(tr) < 0)
-               return -ENODEV;
+       ret = tracing_check_open_get_tr(tr);
+       if (ret)
+               return ret;
 
        /* If this file was open for write, then erase contents */
        if ((file->f_mode & FMODE_WRITE) && (file->f_flags & O_TRUNC)) {
@@ -4352,11 +4366,9 @@ static int show_traces_open(struct inode *inode, struct file *file)
        struct seq_file *m;
        int ret;
 
-       if (tracing_disabled)
-               return -ENODEV;
-
-       if (trace_array_get(tr) < 0)
-               return -ENODEV;
+       ret = tracing_check_open_get_tr(tr);
+       if (ret)
+               return ret;
 
        ret = seq_open(file, &show_traces_seq_ops);
        if (ret) {
@@ -4710,11 +4722,9 @@ static int tracing_trace_options_open(struct inode *inode, struct file *file)
        struct trace_array *tr = inode->i_private;
        int ret;
 
-       if (tracing_disabled)
-               return -ENODEV;
-
-       if (trace_array_get(tr) < 0)
-               return -ENODEV;
+       ret = tracing_check_open_get_tr(tr);
+       if (ret)
+               return ret;
 
        ret = single_open(file, tracing_trace_options_show, inode->i_private);
        if (ret < 0)
@@ -5051,8 +5061,11 @@ static const struct seq_operations tracing_saved_tgids_seq_ops = {
 
 static int tracing_saved_tgids_open(struct inode *inode, struct file *filp)
 {
-       if (tracing_disabled)
-               return -ENODEV;
+       int ret;
+
+       ret = tracing_check_open_get_tr(NULL);
+       if (ret)
+               return ret;
 
        return seq_open(filp, &tracing_saved_tgids_seq_ops);
 }
@@ -5128,8 +5141,11 @@ static const struct seq_operations tracing_saved_cmdlines_seq_ops = {
 
 static int tracing_saved_cmdlines_open(struct inode *inode, struct file *filp)
 {
-       if (tracing_disabled)
-               return -ENODEV;
+       int ret;
+
+       ret = tracing_check_open_get_tr(NULL);
+       if (ret)
+               return ret;
 
        return seq_open(filp, &tracing_saved_cmdlines_seq_ops);
 }
@@ -5293,8 +5309,11 @@ static const struct seq_operations tracing_eval_map_seq_ops = {
 
 static int tracing_eval_map_open(struct inode *inode, struct file *filp)
 {
-       if (tracing_disabled)
-               return -ENODEV;
+       int ret;
+
+       ret = tracing_check_open_get_tr(NULL);
+       if (ret)
+               return ret;
 
        return seq_open(filp, &tracing_eval_map_seq_ops);
 }
@@ -5817,13 +5836,11 @@ static int tracing_open_pipe(struct inode *inode, struct file *filp)
 {
        struct trace_array *tr = inode->i_private;
        struct trace_iterator *iter;
-       int ret = 0;
-
-       if (tracing_disabled)
-               return -ENODEV;
+       int ret;
 
-       if (trace_array_get(tr) < 0)
-               return -ENODEV;
+       ret = tracing_check_open_get_tr(tr);
+       if (ret)
+               return ret;
 
        mutex_lock(&trace_types_lock);
 
@@ -6560,11 +6577,9 @@ static int tracing_clock_open(struct inode *inode, struct file *file)
        struct trace_array *tr = inode->i_private;
        int ret;
 
-       if (tracing_disabled)
-               return -ENODEV;
-
-       if (trace_array_get(tr))
-               return -ENODEV;
+       ret = tracing_check_open_get_tr(tr);
+       if (ret)
+               return ret;
 
        ret = single_open(file, tracing_clock_show, inode->i_private);
        if (ret < 0)
@@ -6594,11 +6609,9 @@ static int tracing_time_stamp_mode_open(struct inode *inode, struct file *file)
        struct trace_array *tr = inode->i_private;
        int ret;
 
-       if (tracing_disabled)
-               return -ENODEV;
-
-       if (trace_array_get(tr))
-               return -ENODEV;
+       ret = tracing_check_open_get_tr(tr);
+       if (ret)
+               return ret;
 
        ret = single_open(file, tracing_time_stamp_mode_show, inode->i_private);
        if (ret < 0)
@@ -6651,10 +6664,11 @@ static int tracing_snapshot_open(struct inode *inode, struct file *file)
        struct trace_array *tr = inode->i_private;
        struct trace_iterator *iter;
        struct seq_file *m;
-       int ret = 0;
+       int ret;
 
-       if (trace_array_get(tr) < 0)
-               return -ENODEV;
+       ret = tracing_check_open_get_tr(tr);
+       if (ret)
+               return ret;
 
        if (file->f_mode & FMODE_READ) {
                iter = __tracing_open(inode, file, true);
@@ -7118,8 +7132,9 @@ static int tracing_err_log_open(struct inode *inode, struct file *file)
        struct trace_array *tr = inode->i_private;
        int ret = 0;
 
-       if (trace_array_get(tr) < 0)
-               return -ENODEV;
+       ret = tracing_check_open_get_tr(tr);
+       if (ret)
+               return ret;
 
        /* If this file was opened for write, then erase contents */
        if ((file->f_mode & FMODE_WRITE) && (file->f_flags & O_TRUNC))
@@ -7170,11 +7185,9 @@ static int tracing_buffers_open(struct inode *inode, struct file *filp)
        struct ftrace_buffer_info *info;
        int ret;
 
-       if (tracing_disabled)
-               return -ENODEV;
-
-       if (trace_array_get(tr) < 0)
-               return -ENODEV;
+       ret = tracing_check_open_get_tr(tr);
+       if (ret)
+               return ret;
 
        info = kzalloc(sizeof(*info), GFP_KERNEL);
        if (!info) {

diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 854dbf4050f8e29903ef42318316e01244cd8cf1..d685c61085c0ddd028ce90db179dc22c8c4630c4 100644 (file)
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -338,6 +338,7 @@ extern struct mutex trace_types_lock;
 
 extern int trace_array_get(struct trace_array *tr);
 extern void trace_array_put(struct trace_array *tr);
+extern int tracing_check_open_get_tr(struct trace_array *tr);
 
 extern int tracing_set_time_stamp_abs(struct trace_array *tr, bool abs);
 extern int tracing_set_clock(struct trace_array *tr, const char *clockstr);

diff --git a/kernel/trace/trace_dynevent.c b/kernel/trace/trace_dynevent.c
index a41fed46c285c3f83726b184b723b4a9e3dd772b..89779eb84a0778ac052e8d1c7300cf4dabdb09e0 100644 (file)
--- a/kernel/trace/trace_dynevent.c
+++ b/kernel/trace/trace_dynevent.c
@@ -174,6 +174,10 @@ static int dyn_event_open(struct inode *inode, struct file *file)
 {
        int ret;
 
+       ret = tracing_check_open_get_tr(NULL);
+       if (ret)
+               return ret;
+
        if ((file->f_mode & FMODE_WRITE) && (file->f_flags & O_TRUNC)) {
                ret = dyn_events_release_all(NULL);
                if (ret < 0)

diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index 9613a757c90270d05bcd6c1bc775d162c2668d60..71ab0a3660f4b521d3b13056e2afde766bf55100 100644 (file)
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -1794,8 +1794,9 @@ ftrace_event_set_open(struct inode *inode, struct file *file)
        struct trace_array *tr = inode->i_private;
        int ret;
 
-       if (trace_array_get(tr) < 0)
-               return -ENODEV;
+       ret = tracing_check_open_get_tr(tr);
+       if (ret)
+               return ret;
 
        if ((file->f_mode & FMODE_WRITE) &&
            (file->f_flags & O_TRUNC))
@@ -1814,8 +1815,9 @@ ftrace_event_set_pid_open(struct inode *inode, struct file *file)
        struct trace_array *tr = inode->i_private;
        int ret;
 
-       if (trace_array_get(tr) < 0)
-               return -ENODEV;
+       ret = tracing_check_open_get_tr(tr);
+       if (ret)
+               return ret;
 
        if ((file->f_mode & FMODE_WRITE) &&
            (file->f_flags & O_TRUNC))

diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
index 9468bd8d44a2d687939b83f081b4bcf5051fd54d..dd18d76bf1bd00beea7b29f5b37f58773df57442 100644 (file)
--- a/kernel/trace/trace_events_hist.c
+++ b/kernel/trace/trace_events_hist.c
@@ -1680,7 +1680,7 @@ static int save_hist_vars(struct hist_trigger_data *hist_data)
        if (var_data)
                return 0;
 
-       if (trace_array_get(tr) < 0)
+       if (tracing_check_open_get_tr(tr))
                return -ENODEV;
 
        var_data = kzalloc(sizeof(*var_data), GFP_KERNEL);