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Commit 6484c71c authored by Oleg Nesterov's avatar Oleg Nesterov Committed by Steven Rostedt
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tracing: Change tracing_fops/snapshot_fops to rely on tracing_get_cpu() 

tracing_open() and tracing_snapshot_open() are racy, the memory
inode->i_private points to can be already freed.

Convert these last users of "inode->i_private == trace_cpu" to
use "i_private = trace_array" and rely on tracing_get_cpu().

v2: incorporate the fix from Steven, tracing_release() must not
    blindly dereference file->private_data unless we know that
    the file was opened for reading.

Link: http://lkml.kernel.org/r/20130723152610.GA23737@redhat.com



Signed-off-by: default avatarOleg Nesterov <oleg@redhat.com>
Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
parent 0bc392ee

kernel/trace/trace.c

+22 −28
Original line number Diff line number Diff line
@@ -2862,9 +2862,9 @@ static const struct seq_operations tracer_seq_ops = { 
};



static struct trace_iterator *

__tracing_open(struct trace_array *tr, struct trace_cpu *tc,

	       struct inode *inode, struct file *file, bool snapshot)

__tracing_open(struct inode *inode, struct file *file, bool snapshot)

{

	struct trace_array *tr = inode->i_private;

	struct trace_iterator *iter;

	int cpu;
@@ -2905,8 +2905,8 @@ __tracing_open(struct trace_array *tr, struct trace_cpu *tc, 
		iter->trace_buffer = &tr->trace_buffer;

	iter->snapshot = snapshot;

	iter->pos = -1;

	iter->cpu_file = tracing_get_cpu(inode);

	mutex_init(&iter->mutex);

	iter->cpu_file = tc->cpu;



	/* Notify the tracer early; before we stop tracing. */

	if (iter->trace && iter->trace->open)
@@ -2986,22 +2986,18 @@ static int tracing_open_generic_tr(struct inode *inode, struct file *filp) 


static int tracing_release(struct inode *inode, struct file *file)

{

	struct trace_array *tr = inode->i_private;

	struct seq_file *m = file->private_data;

	struct trace_iterator *iter;

	struct trace_array *tr;

	int cpu;



	/* Writes do not use seq_file, need to grab tr from inode */

	if (!(file->f_mode & FMODE_READ)) {

		struct trace_cpu *tc = inode->i_private;



		trace_array_put(tc->tr);

		trace_array_put(tr);

		return 0;

	}



	/* Writes do not use seq_file */

	iter = m->private;

	tr = iter->tr;



	mutex_lock(&trace_types_lock);



	for_each_tracing_cpu(cpu) {
@@ -3048,8 +3044,7 @@ static int tracing_single_release_tr(struct inode *inode, struct file *file) 


static int tracing_open(struct inode *inode, struct file *file)

{

	struct trace_cpu *tc = inode->i_private;

	struct trace_array *tr = tc->tr;

	struct trace_array *tr = inode->i_private;

	struct trace_iterator *iter;

	int ret = 0;
@@ -3057,16 +3052,17 @@ static int tracing_open(struct inode *inode, struct file *file) 
		return -ENODEV;



	/* If this file was open for write, then erase contents */

	if ((file->f_mode & FMODE_WRITE) &&

	    (file->f_flags & O_TRUNC)) {

		if (tc->cpu == RING_BUFFER_ALL_CPUS)

	if ((file->f_mode & FMODE_WRITE) && (file->f_flags & O_TRUNC)) {

		int cpu = tracing_get_cpu(inode);



		if (cpu == RING_BUFFER_ALL_CPUS)

			tracing_reset_online_cpus(&tr->trace_buffer);

		else

			tracing_reset(&tr->trace_buffer, tc->cpu);

			tracing_reset(&tr->trace_buffer, cpu);

	}



	if (file->f_mode & FMODE_READ) {

		iter = __tracing_open(tr, tc, inode, file, false);

		iter = __tracing_open(inode, file, false);

		if (IS_ERR(iter))

			ret = PTR_ERR(iter);

		else if (trace_flags & TRACE_ITER_LATENCY_FMT)
@@ -4680,8 +4676,7 @@ struct ftrace_buffer_info { 
#ifdef CONFIG_TRACER_SNAPSHOT

static int tracing_snapshot_open(struct inode *inode, struct file *file)

{

	struct trace_cpu *tc = inode->i_private;

	struct trace_array *tr = tc->tr;

	struct trace_array *tr = inode->i_private;

	struct trace_iterator *iter;

	struct seq_file *m;

	int ret = 0;
@@ -4690,7 +4685,7 @@ static int tracing_snapshot_open(struct inode *inode, struct file *file) 
		return -ENODEV;



	if (file->f_mode & FMODE_READ) {

		iter = __tracing_open(tr, tc, inode, file, true);

		iter = __tracing_open(inode, file, true);

		if (IS_ERR(iter))

			ret = PTR_ERR(iter);

	} else {
@@ -4707,8 +4702,8 @@ static int tracing_snapshot_open(struct inode *inode, struct file *file) 
		ret = 0;



		iter->tr = tr;

		iter->trace_buffer = &tc->tr->max_buffer;

		iter->cpu_file = tc->cpu;

		iter->trace_buffer = &tr->max_buffer;

		iter->cpu_file = tracing_get_cpu(inode);

		m->private = iter;

		file->private_data = m;

	}
@@ -5525,7 +5520,6 @@ trace_create_cpu_file(const char *name, umode_t mode, struct dentry *parent, 
static void

tracing_init_debugfs_percpu(struct trace_array *tr, long cpu)

{

	struct trace_array_cpu *data = per_cpu_ptr(tr->trace_buffer.data, cpu);

	struct dentry *d_percpu = tracing_dentry_percpu(tr, cpu);

	struct dentry *d_cpu;

	char cpu_dir[30]; /* 30 characters should be more than enough */
@@ -5546,7 +5540,7 @@ tracing_init_debugfs_percpu(struct trace_array *tr, long cpu) 


	/* per cpu trace */

	trace_create_cpu_file("trace", 0644, d_cpu,

				&data->trace_cpu, cpu, &tracing_fops);

				tr, cpu, &tracing_fops);



	trace_create_cpu_file("trace_pipe_raw", 0444, d_cpu,

				tr, cpu, &tracing_buffers_fops);
@@ -5559,7 +5553,7 @@ tracing_init_debugfs_percpu(struct trace_array *tr, long cpu) 


#ifdef CONFIG_TRACER_SNAPSHOT

	trace_create_cpu_file("snapshot", 0644, d_cpu,

				&data->trace_cpu, cpu, &snapshot_fops);

				tr, cpu, &snapshot_fops);



	trace_create_cpu_file("snapshot_raw", 0444, d_cpu,

				tr, cpu, &snapshot_raw_fops);
@@ -6125,7 +6119,7 @@ init_tracer_debugfs(struct trace_array *tr, struct dentry *d_tracer) 
			  tr, &tracing_iter_fops);



	trace_create_file("trace", 0644, d_tracer,

			(void *)&tr->trace_cpu, &tracing_fops);

			  tr, &tracing_fops);



	trace_create_file("trace_pipe", 0444, d_tracer,

			  tr, &tracing_pipe_fops);
@@ -6150,7 +6144,7 @@ init_tracer_debugfs(struct trace_array *tr, struct dentry *d_tracer) 


#ifdef CONFIG_TRACER_SNAPSHOT

	trace_create_file("snapshot", 0644, d_tracer,

			  (void *)&tr->trace_cpu, &snapshot_fops);

			  tr, &snapshot_fops);

#endif



	for_each_tracing_cpu(cpu)