From: Steven Rostedt (VMware) rostedt@goodmis.org
commit 194c2c74f5532e62c218adeb8e2b683119503907 upstream.
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: 607e2ea167e56 ("tracing: Set up infrastructure to allow tracers for instances") Signed-off-by: Steven Rostedt (VMware) rostedt@goodmis.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- kernel/trace/trace.c | 17 +++++++++++++++-- 1 file changed, 15 insertions(+), 2 deletions(-)
--- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -4355,9 +4355,14 @@ static int show_traces_open(struct inode 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 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 trac 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