From 1a11126bcb7c93c289bf3218fa546fd3b0c0df8b Mon Sep 17 00:00:00 2001 From: Oleg Nesterov Date: Fri, 26 Jul 2013 19:25:32 +0200 Subject: [PATCH] tracing: Turn event/id->i_private into call->event.type event_id_read() is racy, ftrace_event_call can be already freed by trace_remove_event_call() callers. Change event_create_dir() to pass "data = call->event.type", this is all event_id_read() needs. ftrace_event_id_fops no longer needs tracing_open_generic(). We add the new helper, event_file_data(), to read ->i_private, it will have more users. Note: currently ACCESS_ONCE() and "id != 0" check are not needed, but we are going to change event_remove/rmdir to clear ->i_private. Link: http://lkml.kernel.org/r/20130726172532.GA3605@redhat.com Reviewed-by: Masami Hiramatsu Signed-off-by: Oleg Nesterov Signed-off-by: Steven Rostedt --- kernel/trace/trace_events.c | 18 +++++++++++++----- 1 file changed, 13 insertions(+), 5 deletions(-) diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c index 898f868..c2d13c5 100644 --- a/kernel/trace/trace_events.c +++ b/kernel/trace/trace_events.c @@ -409,6 +409,11 @@ static void put_system(struct ftrace_subsystem_dir *dir) mutex_unlock(&event_mutex); } +static void *event_file_data(struct file *filp) +{ + return ACCESS_ONCE(file_inode(filp)->i_private); +} + /* * Open and update trace_array ref count. * Must have the current trace_array passed to it. @@ -946,14 +951,18 @@ static int trace_format_open(struct inode *inode, struct file *file) static ssize_t event_id_read(struct file *filp, char __user *ubuf, size_t cnt, loff_t *ppos) { - struct ftrace_event_call *call = filp->private_data; + int id = (long)event_file_data(filp); char buf[32]; int len; if (*ppos) return 0; - len = sprintf(buf, "%d\n", call->event.type); + if (unlikely(!id)) + return -ENODEV; + + len = sprintf(buf, "%d\n", id); + return simple_read_from_buffer(ubuf, cnt, ppos, buf, len); } @@ -1240,7 +1249,6 @@ static const struct file_operations ftrace_event_format_fops = { }; static const struct file_operations ftrace_event_id_fops = { - .open = tracing_open_generic, .read = event_id_read, .llseek = default_llseek, }; @@ -1488,8 +1496,8 @@ event_create_dir(struct dentry *parent, #ifdef CONFIG_PERF_EVENTS if (call->event.type && call->class->reg) - trace_create_file("id", 0444, file->dir, call, - id); + trace_create_file("id", 0444, file->dir, + (void *)(long)call->event.type, id); #endif /* -- 2.7.4