linux-kernel - Re: [PATCH 3/6] tracefs: dentry lookup crapectomy

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Date: Wed, 31 Jan 2024 00:07:32 +0000
From: Al Viro <viro@...iv.linux.org.uk>
To: Steven Rostedt <rostedt@...dmis.org>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>,
	Masami Hiramatsu <mhiramat@...nel.org>,
	linux-kernel@...r.kernel.org, linux-trace-kernel@...r.kernel.org
Subject: Re: [PATCH 3/6] tracefs: dentry lookup crapectomy

On Tue, Jan 30, 2024 at 06:55:36PM -0500, Steven Rostedt wrote:

> Actually it's the tracefs_start_creating() locks the inode, the
> eventfs_start_creating() doesn't.

Right.

> > 
> > >  	if (unlikely(!inode))
> > >  		return eventfs_failed_creating(dentry);  
> > 
> > ... and that still unlocks it.

This is still bogus, though - both the stray dput() and
dropping a reference to internal mount.

struct dentry *eventfs_failed_creating(struct dentry *dentry)
{
        dput(dentry);
	simple_release_fs(&tracefs_mount, &tracefs_mount_count);
	return NULL;
}