tracing: Change tracing_entries_fops to rely on tracing_get_cpu()

commit 0bc392ee46d0fd8e6b678457ef71f074f19a03c5 upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 12 insertions, 37 deletions

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 801d72b84a2a..83fba3c576e8 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -2975,23 +2975,6 @@ int tracing_open_generic_tr(struct inode *inode, struct file *filp)
         return 0;
 }
 
-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;
@@ -3045,15 +3028,6 @@ 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;
@@ -4374,15 +4348,16 @@ 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;
 
@@ -4409,7 +4384,7 @@ 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);
 
@@ -4421,7 +4396,8 @@ 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;
 
@@ -4435,8 +4411,7 @@ 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;
 
@@ -4884,11 +4859,11 @@ 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 = {
@@ -5572,7 +5547,7 @@ 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,
@@ -6148,7 +6123,7 @@ 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);