From mboxrd@z Thu Jan 1 00:00:00 1970 From: Steven Rostedt Subject: [PATCH 3/7 v2] tracing: Get trace_array reference for available_tracers files Date: Fri, 11 Oct 2019 20:57:50 -0400 Message-ID: <20191012005920.942012497@goodmis.org> References: <20191012005747.210722465@goodmis.org> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Return-path: Sender: linux-kernel-owner@vger.kernel.org To: linux-kernel@vger.kernel.org Cc: Linus Torvalds , Ingo Molnar , Andrew Morton , Matthew Garrett , James Morris James Morris , LSM List , Linux API , Ben Hutchings , Al Viro , stable@vger.kernel.org List-Id: linux-api@vger.kernel.org From: "Steven Rostedt (VMware)" As instances may have different tracers available, we need to look at the trace_array descriptor that shows lists the available tracers for the instance. But there's a race between opening the file and the admin from 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) --- kernel/trace/trace.c | 17 +++++++++++++++-- 1 file changed, 15 insertions(+), 2 deletions(-) diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index 252f79c435f8..fa7d813b04c6 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -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 -- 2.23.0