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Date: Tue, 28 Jan 2025 03:07:28 +0000
From: Al Viro <viro@zeniv.linux.org.uk>
To: Viacheslav Dubeyko <slava@dubeyko.com>
Cc: ceph-devel@vger.kernel.org, idryomov@gmail.com,
	linux-fsdevel@vger.kernel.org, pdonnell@redhat.com,
	amarkuze@redhat.com, Slava.Dubeyko@ibm.com
Subject: Re: [PATCH] ceph: is_root_ceph_dentry() cleanup
Message-ID: <20250128030728.GN1977892@ZenIV>
References: <20250128011023.55012-1-slava@dubeyko.com>
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Sender: Al Viro <viro@ftp.linux.org.uk>

On Mon, Jan 27, 2025 at 05:10:23PM -0800, Viacheslav Dubeyko wrote:
> From: Viacheslav Dubeyko <Slava.Dubeyko@ibm.com>
> 
> This patch introduces CEPH_HIDDEN_DIR_NAME. It
> declares name of the hidden directory .ceph in
> the include/linux/ceph/ceph_fs.h instead of hiding
> it in dir.c file. Also hardcoded length of the name
> is changed on strlen(CEPH_HIDDEN_DIR_NAME).

Hmm...

Speaking of that area
	* how the hell could ceph_lookup() ever be called with dentry
that is *NOT* negative?  VFS certainly won't do that; I'm not sure about
ceph_handle_notrace_create(), but it doesn't look like that's possible
without server being malicious (if it's possible at all).

	* speaking of malicious servers, what happens if
it gets CEPH_MDS_OP_LOOKUP and it returns a normal reply to positive
lookup, but with cpu_to_le32(-ENOENT) shoved into head->result?
	AFAICS, ceph_handle_snapdir() will be called with dentry
that is already made positive; results will not be pretty...