tracing: Change tracing_entries_fops to rely on tracing_get_cpu()

tracing_open_generic_tc() is racy, the memory inode->i_private
points to can be already freed.

1. Change its last user, tracing_entries_fops, to use
   tracing_*_generic_tr() instead.

2. Change debugfs_create_file("buffer_size_kb", data) callers
   to pass "data = tr".

3. Change tracing_entries_read() and tracing_entries_write() to
   use tracing_get_cpu().

4. Kill the no longer used tracing_open_generic_tc() and
   tracing_release_generic_tc().

Link: http://lkml.kernel.org/r/20130723152606.GA23730@redhat.com
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index e29dc8f..68b4685 100644 (file)
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -2984,23 +2984,6 @@ static int tracing_open_generic_tr(struct inode *inode, struct file *filp)
        return 0;
 }
 
-static int tracing_open_generic_tc(struct inode *inode, struct file *filp)
-{
-       struct trace_cpu *tc = inode->i_private;
-       struct trace_array *tr = tc->tr;
-
-       if (tracing_disabled)
-               return -ENODEV;
-
-       if (trace_array_get(tr) < 0)
-               return -ENODEV;
-
-       filp->private_data = inode->i_private;
-
-       return 0;
-       
-}
-
 static int tracing_release(struct inode *inode, struct file *file)
 {
        struct seq_file *m = file->private_data;
@@ -3054,15 +3037,6 @@ static int tracing_release_generic_tr(struct inode *inode, struct file *file)
        return 0;
 }
 
-static int tracing_release_generic_tc(struct inode *inode, struct file *file)
-{
-       struct trace_cpu *tc = inode->i_private;
-       struct trace_array *tr = tc->tr;
-
-       trace_array_put(tr);
-       return 0;
-}
-
 static int tracing_single_release_tr(struct inode *inode, struct file *file)
 {
        struct trace_array *tr = inode->i_private;
@@ -4382,15 +4356,16 @@ static ssize_t
 tracing_entries_read(struct file *filp, char __user *ubuf,
                     size_t cnt, loff_t *ppos)
 {
-       struct trace_cpu *tc = filp->private_data;
-       struct trace_array *tr = tc->tr;
+       struct inode *inode = file_inode(filp);
+       struct trace_array *tr = inode->i_private;
+       int cpu = tracing_get_cpu(inode);
        char buf[64];
        int r = 0;
        ssize_t ret;
 
        mutex_lock(&trace_types_lock);
 
-       if (tc->cpu == RING_BUFFER_ALL_CPUS) {
+       if (cpu == RING_BUFFER_ALL_CPUS) {
                int cpu, buf_size_same;
                unsigned long size;
 
@@ -4417,7 +4392,7 @@ tracing_entries_read(struct file *filp, char __user *ubuf,
                } else
                        r = sprintf(buf, "X\n");
        } else
-               r = sprintf(buf, "%lu\n", per_cpu_ptr(tr->trace_buffer.data, tc->cpu)->entries >> 10);
+               r = sprintf(buf, "%lu\n", per_cpu_ptr(tr->trace_buffer.data, cpu)->entries >> 10);
 
        mutex_unlock(&trace_types_lock);
 
@@ -4429,7 +4404,8 @@ static ssize_t
 tracing_entries_write(struct file *filp, const char __user *ubuf,
                      size_t cnt, loff_t *ppos)
 {
-       struct trace_cpu *tc = filp->private_data;
+       struct inode *inode = file_inode(filp);
+       struct trace_array *tr = inode->i_private;
        unsigned long val;
        int ret;
 
@@ -4443,8 +4419,7 @@ tracing_entries_write(struct file *filp, const char __user *ubuf,
 
        /* value is in KB */
        val <<= 10;
-
-       ret = tracing_resize_ring_buffer(tc->tr, val, tc->cpu);
+       ret = tracing_resize_ring_buffer(tr, val, tracing_get_cpu(inode));
        if (ret < 0)
                return ret;
 
@@ -4892,11 +4867,11 @@ static const struct file_operations tracing_pipe_fops = {
 };
 
 static const struct file_operations tracing_entries_fops = {
-       .open           = tracing_open_generic_tc,
+       .open           = tracing_open_generic_tr,
        .read           = tracing_entries_read,
        .write          = tracing_entries_write,
        .llseek         = generic_file_llseek,
-       .release        = tracing_release_generic_tc,
+       .release        = tracing_release_generic_tr,
 };
 
 static const struct file_operations tracing_total_entries_fops = {
@@ -5580,7 +5555,7 @@ tracing_init_debugfs_percpu(struct trace_array *tr, long cpu)
                                tr, cpu, &tracing_stats_fops);
 
        trace_create_cpu_file("buffer_size_kb", 0444, d_cpu,
-                               &data->trace_cpu, cpu, &tracing_entries_fops);
+                               tr, cpu, &tracing_entries_fops);
 
 #ifdef CONFIG_TRACER_SNAPSHOT
        trace_create_cpu_file("snapshot", 0644, d_cpu,
@@ -6156,7 +6131,7 @@ init_tracer_debugfs(struct trace_array *tr, struct dentry *d_tracer)
                          tr, &tracing_pipe_fops);
 
        trace_create_file("buffer_size_kb", 0644, d_tracer,
-                       (void *)&tr->trace_cpu, &tracing_entries_fops);
+                         tr, &tracing_entries_fops);
 
        trace_create_file("buffer_total_size_kb", 0444, d_tracer,
                          tr, &tracing_total_entries_fops);