linux-kernel - Re: [PATCH] kernfs: Drop kernfs_rwsem while invoking lookup_positive

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Message-ID: <20250221074957.6Gqax5ib@linutronix.de>
Date: Fri, 21 Feb 2025 08:49:57 +0100
From: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To: Al Viro <viro@...iv.linux.org.uk>
Cc: syzbot <syzbot+ecccecbc636b455f9084@...kaller.appspotmail.com>,
	gregkh@...uxfoundation.org, linux-kernel@...r.kernel.org,
	syzkaller-bugs@...glegroups.com, tj@...nel.org,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH] kernfs: Drop kernfs_rwsem while invoking
 lookup_positive_unlocked().

On 2025-02-20 20:39:24 [+0000], Al Viro wrote:
> On Tue, Feb 18, 2025 at 05:39:38PM +0100, Sebastian Andrzej Siewior wrote:
> 
> > +	scoped_guard(rcu) {
> > +		knparent = find_next_ancestor(kn, NULL);
> > +		if (WARN_ON(!knparent)) {
> > +			dput(dentry);
> > +			return ERR_PTR(-EINVAL);
> > +		}
> 
> NAK.  dput() is blocking; you *can't* do that under rcu_read_lock().

Thank you.
Since it got merged, let me do another one on top.

Sebastian