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Wed, 13 Nov 2024 05:17:11 -0500 (EST) Message-ID: Date: Wed, 13 Nov 2024 11:17:10 +0100 Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 0/4] pidfs: implement file handle support Content-Language: en-GB To: "Darrick J. Wong" Cc: Christian Brauner , Jeff Layton , Amir Goldstein , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, christian@brauner.io, paul@paul-moore.com, bluca@debian.org, Chuck Lever References: <20241101135452.19359-1-erin.shepherd@e43.eu> <20241112-banknoten-ehebett-211d59cb101e@brauner> <05af74a9-51cc-4914-b285-b50d69758de7@e43.eu> <20241113004011.GG9421@frogsfrogsfrogs> From: Erin Shepherd In-Reply-To: <20241113004011.GG9421@frogsfrogsfrogs> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 13/11/2024 01:40, Darrick J. Wong wrote: >> Hmm, I guess I might have made that possible, though I'm certainly not >> familiar enough with the internals of nfsd to be able to test if I've done >> so. > AFAIK check_export() in fs/nfsd/export.c spells this it out: > > /* There are two requirements on a filesystem to be exportable. > * 1: We must be able to identify the filesystem from a number. > * either a device number (so FS_REQUIRES_DEV needed) > * or an FSID number (so NFSEXP_FSID or ->uuid is needed). > * 2: We must be able to find an inode from a filehandle. > * This means that s_export_op must be set. > * 3: We must not currently be on an idmapped mount. > */ > > Granted I've been wrong on account of stale docs before. :$ > > Though it would be kinda funny if you *could* mess with another > machine's processes over NFS. > > --D To be clear I'm not familiar enough with the workings of nfsd to tell if pidfs fails those requirements and therefore wouldn't become exportable as a result of this patch, though I gather from you're message that we're in the clear? Regardless I think my question is: do we think either those requirements could change in the future, or the properties of pidfs could change in the future, in ways that could accidentally make the filesystem exportable? I guess though that the same concern would apply to cgroupfs and it hasn't posed an issue so far. - Erin