tracing: Change remove_event_file_dir() to clear "d_subdirs"->i_private (bf682c31) · Commits · 戴 / test

Change remove_event_file_dir() to clear ->i_private for every file we are going to remove. We need to check file->dir != NULL because event_create_dir() can fail. debugfs_remove_recursive(NULL) is fine but the patch moves it under the same check anyway for readability. spin_lock(d_lock) and "d_inode != NULL" check are not needed afaics, but I do not understand this code enough. tracing_open_generic_file() and tracing_release_generic_file() can go away, ftrace_enable_fops and ftrace_event_filter_fops() use tracing_open_generic() but only to check tracing_disabled. This fixes all races with event_remove() or instance_delete(). f_op->read/write/whatever can never use the freed file/call, all event/* files were changed to check and use ->i_private under event_mutex. Note: this doesn't not fix other problems, event_remove() can destroy the active ftrace_event_call, we need more changes but those changes are completely orthogonal. Link: http://lkml.kernel.org/r/20130728183527.GB16723@redhat.com Reviewed-by:

Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Signed-off-by:

Oleg Nesterov <oleg@redhat.com> Signed-off-by:

Steven Rostedt <rostedt@goodmis.org>

kernel/trace/trace_events.c

+15 −32

Original line number	Diff line number	Diff line
		@@ -428,39 +428,23 @@ static void event_file_data(struct file filp)

		static void remove_event_file_dir(struct ftrace_event_file *file)
		{
		list_del(&file->list);
		debugfs_remove_recursive(file->dir);
		remove_subsystem(file->system);
		kmem_cache_free(file_cachep, file);
		}

		/*
		* Open and update trace_array ref count.
		* Must have the current trace_array passed to it.
		*/
		static int tracing_open_generic_file(struct inode inode, struct file filp)
		{
		struct ftrace_event_file *file = inode->i_private;
		struct trace_array *tr = file->tr;
		int ret;
		struct dentry *dir = file->dir;
		struct dentry *child;

		if (trace_array_get(tr) < 0)
		return -ENODEV;

		ret = tracing_open_generic(inode, filp);
		if (ret < 0)
		trace_array_put(tr);
		return ret;
		if (dir) {
		spin_lock(&dir->d_lock); /* probably unneeded */
		list_for_each_entry(child, &dir->d_subdirs, d_u.d_child) {
		if (child->d_inode) /* probably unneeded */
		child->d_inode->i_private = NULL;
		}
		spin_unlock(&dir->d_lock);

		static int tracing_release_generic_file(struct inode inode, struct file filp)
		{
		struct ftrace_event_file *file = inode->i_private;
		struct trace_array *tr = file->tr;

		trace_array_put(tr);
		debugfs_remove_recursive(dir);
		}

		return 0;
		list_del(&file->list);
		remove_subsystem(file->system);
		kmem_cache_free(file_cachep, file);
		}

		/*
		@@ -1281,10 +1265,9 @@ static const struct file_operations ftrace_set_event_fops = {
		};

		static const struct file_operations ftrace_enable_fops = {
		.open = tracing_open_generic_file,
		.open = tracing_open_generic,
		.read = event_enable_read,
		.write = event_enable_write,
		.release = tracing_release_generic_file,
		.llseek = default_llseek,
		};

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