From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from zeniv.linux.org.uk (zeniv.linux.org.uk [62.89.141.173]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 7EFA62B9AA for ; Thu, 20 Feb 2025 20:39:26 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=62.89.141.173 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1740083969; cv=none; b=jp1uyhZ2IgUaoGjtZRJvSgHwvt130FPhZJcbPdsdEjJPmTqOmRV4+pwXjICn3yh3qpS4xR24VE/7kk6cEeXP1wa4OmJJCcT/sDWD30pkTkb5HVZ/9elHtRnE+7KvfKMYaUyutyvofVHJ5GbMtnlvgo3KPmwwZMMKw42rJznDQMo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1740083969; c=relaxed/simple; bh=GXmby5r7jmhWHpKMuDVtnZrpYoSfgQYzXmWWqJTIRj0=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=Ccs0XM3GJNGwbspATEEzKpnYMRLiCc19mCEpH+RN91piIwzueGby3q5y6nDKXUX+ycpA1qY7ajQ+7W7xvCsrXMZbP1Jp1NSpMxjaY/juqwUe+6DENzo26cGzWmg78LgU6Oz23g7eV9gcbT6negmW8qG2Ya+y8VQkSsoSV7RITnw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=zeniv.linux.org.uk; spf=none smtp.mailfrom=ftp.linux.org.uk; dkim=pass (2048-bit key) header.d=linux.org.uk header.i=@linux.org.uk header.b=uf+7sJ9L; arc=none smtp.client-ip=62.89.141.173 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=zeniv.linux.org.uk Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=ftp.linux.org.uk Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=linux.org.uk header.i=@linux.org.uk header.b="uf+7sJ9L" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=linux.org.uk; s=zeniv-20220401; h=Sender:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=F4MQba6vka5aBfrAWeL4MHPRxEgttf2PmNBq0voUdu8=; b=uf+7sJ9LuyJoTh/5acAs/DXLHz i/mNivKqEHT0vSAoGYnlRfy3UTyQVOOOXWMRn/pjSggCGV6o21aW/C5xWcBNzAXCDWVltk+lY405C P4UkLxAri+TBehx2uTa8QQ2oSTN9o2Ui7Mub4Z708KYIrK9HxqN3vCoa39OSYiVdrAo+Q73G0GMto QFvEyWQXNtJL/BmDnM72rMlX0Ojm1nGzE3+8/Nw8Rl7iHAdMoPxo1Q++USiAXBVGy/So3UyugVeKY auqJtD8wKKDUWJbFzWG/jAnL4wCHOGBr8hKkZn+HlqQUmHglAf3UzXG9NUBEt6styVNHGrVDjm8JC FfVko1MQ==; Received: from viro by zeniv.linux.org.uk with local (Exim 4.98 #2 (Red Hat Linux)) id 1tlDKO-0000000376C-0keQ; Thu, 20 Feb 2025 20:39:24 +0000 Date: Thu, 20 Feb 2025 20:39:24 +0000 From: Al Viro To: Sebastian Andrzej Siewior Cc: syzbot , gregkh@linuxfoundation.org, linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com, tj@kernel.org, Thomas Gleixner Subject: Re: [PATCH] kernfs: Drop kernfs_rwsem while invoking lookup_positive_unlocked(). Message-ID: <20250220203924.GL1977892@ZenIV> References: <67b45276.050a0220.173698.004f.GAE@google.com> <20250218163938.xmvjlJ0K@linutronix.de> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250218163938.xmvjlJ0K@linutronix.de> Sender: Al Viro 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().