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Salah Triki , Nicolas Pitre , Anders Larsen , Alexander Viro , David Sterba , Chris Mason , Gao Xiang , Chao Yu , Yue Hu , Jeffle Xu , Sandeep Dhavale , Hongbo Li , Chunhai Guo , Jan Kara , Theodore Ts'o , Andreas Dilger , Jaegeuk Kim , OGAWA Hirofumi , David Woodhouse , Richard Weinberger , Dave Kleikamp , Ryusuke Konishi , Viacheslav Dubeyko , Konstantin Komarov , Mark Fasheh , Joel Becker , Joseph Qi , Mike Marshall , Martin Brandenburg , Miklos Szeredi , Phillip Lougher , Carlos Maiolino , Hugh Dickins , Baolin Wang , Andrew Morton , Namjae Jeon , Sungjong Seo , Yuezhang Mo , Alexander Aring , Andreas Gruenbacher , Jonathan Corbet , "Matthew Wilcox (Oracle)" , Eric Van Hensbergen , Latchesar Ionkov , Dominique Martinet , Christian Schoenebeck , Xiubo Li , Ilya Dryomov , Trond Myklebust , Anna Schumaker , Steve French , Paulo Alcantara , Ronnie Sahlberg , Shyam Prasad N , Tom Talpey , Bharath SM , Hans de Goede , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-btrfs@vger.kernel.org, linux-erofs@lists.ozlabs.org, linux-ext4@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, linux-mtd@lists.infradead.org, jfs-discussion@lists.sourceforge.net, linux-nilfs@vger.kernel.org, ntfs3@lists.linux.dev, ocfs2-devel@lists.linux.dev, devel@lists.orangefs.org, linux-unionfs@vger.kernel.org, linux-xfs@vger.kernel.org, linux-mm@kvack.org, gfs2@lists.linux.dev, linux-doc@vger.kernel.org, v9fs@lists.linux.dev, ceph-devel@vger.kernel.org, linux-nfs@vger.kernel.org, linux-cifs@vger.kernel.org, samba-technical@lists.samba.org Date: Tue, 13 Jan 2026 12:06:42 -0500 In-Reply-To: References: <20260108-setlease-6-20-v1-0-ea4dec9b67fa@kernel.org> <8af369636c32b868f83669c49aea708ca3b894ac.camel@kernel.org> <20260113-mondlicht-raven-82fc4eb70e9d@brauner> Autocrypt: addr=jlayton@kernel.org; prefer-encrypt=mutual; keydata=mQINBE6V0TwBEADXhJg7s8wFDwBMEvn0qyhAnzFLTOCHooMZyx7XO7dAiIhDSi7G1NPxw 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Evolution 3.58.2 (3.58.2-1.fc43) MIME-Version: 1.0 X-Stat-Signature: bgy4nkiumy9fwmoweiwu3xuuy56uzgnd X-Rspam-User: X-Rspamd-Queue-Id: F3302100008 X-Rspamd-Server: rspam08 X-HE-Tag: 1768324012-855849 X-HE-Meta: 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29rC790tdlm9JkSJzBj6IcNQm9VyoC1tKZ7sF7jzkKAtlL4Z+StFZVIFw0uFreHM0ewL0hNff9IzPdGTGpsEqeLfVoeAEscJ/14pGMcxhB0lma3VqSR9stvBIMUevlaJUYUI1polJNyE94eiMge5xRqk9r4S8nL/ELIAosm6eYhj5WJynVU5aseXmwuBHVRBrRACvE/cWck3hbR+CL15ddTPHt7HVfOgP0v34JBY8h8LNUNx1ILtB3N+gKOI4q3ZIv0ovlGu93EHrSnSEmS64qUZrDsqo1QAUgbpOiyUmNDjvQrj0/SFQt+3CB+9qWd4lF6On X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue, 2026-01-13 at 06:54 -0800, Christoph Hellwig wrote: > On Tue, Jan 13, 2026 at 09:54:15AM +0100, Christian Brauner wrote: > > I don't think we want to expose cgroupfs via NFS that's super weird. > > It's like remote partial resource management and it would be very > > strange if a remote process suddenly would be able to move things aroun= d > > in the cgroup tree. So I would prefer to not do this. > >=20 > > So my preference would be to really sever file handles from the export > > mechanism so that we can allow stuff like pidfs and nsfs and cgroupfs t= o > > use file handles via name_to_handle_at() and open_by_handle_at() withou= t > > making them exportable. >=20 > I don't understand this discussion. If someone really wants to > expose say cgroupfs to the network they'll find a way, be that using > a userspace nfs server, samba, 9p or a custom fuse thing. What's the > benefit of explicitly prohibiting a knfsd export? >=20 > (not that I think any of this makes much sense to start with) Fair point, but it's not that hard to conceive of a situation where someone inadvertantly exports cgroupfs or some similar filesystem: Could you end up exporting /sys if it's bind mounted into a container somewhere? Bear in mind that exportfs does allow mountpoint crossing, etc. nfsd is a network service, so I think the kernel needs to be quite conservative about what filehandles it can access. --=20 Jeff Layton