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tracing: Get trace_array reference for available_tracers files 

As instances may have different tracers available, we need to look at the
trace_array descriptor that shows the list of the available tracers for the
instance. But there's a race between opening the file and an admin
deleting the instance. The trace_array_get() needs to be called before
accessing the trace_array.

Cc: stable@vger.kernel.org
Fixes: 607e2ea167 ("tracing: Set up infrastructure to allow tracers for instances")
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
alistair/sunxi64-5.4-dsi
Steven Rostedt (VMware) 2019-10-11 18:19:17 -04:00
parent 9ef16693af
commit 194c2c74f5
1 changed files with 15 additions and 2 deletions
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17
kernel/trace/trace.c
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@ -4355,9 +4355,14 @@ static int show_traces_open(struct inode *inode, struct file *file)
if (tracing_disabled)
return -ENODEV;
if (trace_array_get(tr) < 0)
return -ENODEV;
ret = seq_open(file, &show_traces_seq_ops);
if (ret)
if (ret) {
trace_array_put(tr);
return ret;
}
m = file->private_data;
m->private = tr;
@ -4365,6 +4370,14 @@ static int show_traces_open(struct inode *inode, struct file *file)
return 0;
}
static int show_traces_release(struct inode *inode, struct file *file)
{
struct trace_array *tr = inode->i_private;
trace_array_put(tr);
return seq_release(inode, file);
}
static ssize_t
tracing_write_stub(struct file *filp, const char __user *ubuf,
size_t count, loff_t *ppos)
@ -4395,8 +4408,8 @@ static const struct file_operations tracing_fops = {
static const struct file_operations show_traces_fops = {
.open = show_traces_open,
.read = seq_read,
.release = seq_release,
.llseek = seq_lseek,
.release = show_traces_release,
};
static ssize_t