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Subject[for-next-3.11][PATCH 4/9] tracing: Change tracing_stats_fops to rely on tracing_get_cpu()
From: Oleg Nesterov <oleg@redhat.com>

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

1. Change one of its users, tracing_stats_fops, to use
tracing_*_generic_tr() instead.

2. Change trace_create_cpu_file("stats", data) to pass "data = tr".

3. Change tracing_stats_read() to use tracing_get_cpu().

Link: http://lkml.kernel.org/r/20130723152603.GA23727@redhat.com

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
kernel/trace/trace.c | 13 ++++++-------
1 file changed, 6 insertions(+), 7 deletions(-)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 30c058a..e29dc8f 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -2982,7 +2982,6 @@ static int tracing_open_generic_tr(struct inode *inode, struct file *filp)
filp->private_data = inode->i_private;

return 0;
-
}

static int tracing_open_generic_tc(struct inode *inode, struct file *filp)
@@ -5285,14 +5284,14 @@ static ssize_t
tracing_stats_read(struct file *filp, char __user *ubuf,
size_t count, 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;
struct trace_buffer *trace_buf = &tr->trace_buffer;
+ int cpu = tracing_get_cpu(inode);
struct trace_seq *s;
unsigned long cnt;
unsigned long long t;
unsigned long usec_rem;
- int cpu = tc->cpu;

s = kmalloc(sizeof(*s), GFP_KERNEL);
if (!s)
@@ -5345,10 +5344,10 @@ tracing_stats_read(struct file *filp, char __user *ubuf,
}

static const struct file_operations tracing_stats_fops = {
- .open = tracing_open_generic_tc,
+ .open = tracing_open_generic_tr,
.read = tracing_stats_read,
.llseek = generic_file_llseek,
- .release = tracing_release_generic_tc,
+ .release = tracing_release_generic_tr,
};

#ifdef CONFIG_DYNAMIC_FTRACE
@@ -5578,7 +5577,7 @@ tracing_init_debugfs_percpu(struct trace_array *tr, long cpu)
tr, cpu, &tracing_buffers_fops);

trace_create_cpu_file("stats", 0444, d_cpu,
- &data->trace_cpu, cpu, &tracing_stats_fops);
+ tr, cpu, &tracing_stats_fops);

trace_create_cpu_file("buffer_size_kb", 0444, d_cpu,
&data->trace_cpu, cpu, &tracing_entries_fops);
--
1.7.10.4



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