NFS clients may bypass restrictive directory permissions by using
open_by_handle() (or other available OS system call) to guess the
filehandles for files below that directory.
In order to harden knfsd servers against this attack, create a method to
sign and verify filehandles using SipHash-2-4 as a MAC (Message
Authentication Code). According to
https://cr.yp.to/siphash/siphash-20120918.pdf, SipHash can be used as a
MAC, and our use of SipHash-2-4 provides a low 1 in 2^64 chance of forgery.
Filehandles that have been signed cannot be tampered with, nor can
clients reasonably guess correct filehandles and hashes that may exist in
parts of the filesystem they cannot access due to directory permissions.
Append the 8 byte SipHash to encoded filehandles for exports that have set
the "sign_fh" export option. Filehandles received from clients are
verified by comparing the appended hash to the expected hash. If the MAC
does not match the server responds with NFS error _STALE. If unsigned
filehandles are received for an export with "sign_fh" they are rejected
with NFS error _STALE.
Signed-off-by: Benjamin Coddington <bcodding@hammerspace.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Sphinx reports htmldocs indentation warnings:
Documentation/filesystems/nfs/nfsd-io-modes.rst:58: ERROR: Unexpected indentation. [docutils]
Documentation/filesystems/nfs/nfsd-io-modes.rst:59: WARNING: Block quote ends without a blank line; unexpected unindent. [docutils]
These caused the lists to be shown as long running paragraphs merged
with their previous paragraphs.
Fix these by separating the lists with a blank line.
Fixes: fa8d4e6784 ("NFSD: add Documentation/filesystems/nfs/nfsd-io-modes.rst")
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Closes: https://lore.kernel.org/linux-next/20251202152506.7a2d2d41@canb.auug.org.au/
Signed-off-by: Bagas Sanjaya <bagasdotme@gmail.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Reviewed-by: Randy Dunlap <rdunlap@infradead.org>
Tested-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
This document details the NFSD IO modes that are configurable using
NFSD's experimental debugfs interfaces:
/sys/kernel/debug/nfsd/io_cache_read
/sys/kernel/debug/nfsd/io_cache_write
This document will evolve as NFSD's interfaces do (e.g. if/when NFSD's
debugfs interfaces are replaced with per-export controls).
Future updates will provide more specific guidance and howto
information to help others use and evaluate NFSD's IO modes:
BUFFERED, DONTCACHE and DIRECT.
Signed-off-by: Mike Snitzer <snitzer@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Sphinx reports htmldocs warnings:
Documentation/filesystems/nfs/nfsd-maintainer-entry-profile.rst:185: ERROR: Unknown target name: "nfsd". [docutils]
Documentation/filesystems/nfs/nfsd-maintainer-entry-profile.rst:188: ERROR: Unknown target name: "nfsdn". [docutils]
Documentation/filesystems/nfs/nfsd-maintainer-entry-profile.rst:192: ERROR: Unknown target name: "nfsd4m". [docutils]
These are due to Sphinx confusing function name prefixes for external
link syntax. Fix the warnings by inlining the prefixes.
Fixes: 3a1ce35030 ("NFSD: Add a subsystem policy document")
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Closes: https://lore.kernel.org/linux-next/20251117174218.29365f30@canb.auug.org.au/
Signed-off-by: Bagas Sanjaya <bagasdotme@gmail.com>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Steer contributors to NFSD's patchworks instance, list our patch
submission preferences, and more. The new document is based on the
existing netdev and xfs subsystem policy documents.
This is an attempt to add transparency to the process of accepting
contributions to NFSD and getting them merged upstream.
Suggested-by: "Darrick J. Wong" <djwong@kernel.org>
Cc: Luis Chamberlain <mcgrof@kernel.org>
Cc: Martin K. Petersen <martin.petersen@oracle.com>
Reviewed-by: NeilBrown <neil@brown.name>
[ cel: Hand-edits to address review comments ]
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
We do not and cannot support file locking with NFS reexport over
NFSv4.x for the same reason we don't do it for NFSv3: NFS reexport
server reboot cannot allow clients to recover locks because the source
NFS server has not rebooted, and so it is not in grace. Since the
source NFS server is not in grace, it cannot offer any guarantees that
the file won't have been changed between the locks getting lost and
any attempt to recover/reclaim them. The same applies to delegations
and any associated locks, so disallow them too.
Clients are no longer allowed to get file locks or delegations from a
reexport server, any attempts will fail with operation not supported.
Update the "Reboot recovery" section accordingly in
Documentation/filesystems/nfs/reexport.rst
Signed-off-by: Mike Snitzer <snitzer@kernel.org>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Re-enabling NFSv3 LOCALIO is made more complex (than NFSv4) because v3
is stateless. As such, the hueristic used to identify a LOCALIO probe
point is more adhoc by nature: if/when NFSv3 client IO begins to
complete again in terms of normal RPC-based NFSv3 server IO, attempt
nfs_local_probe_async().
Care is taken to throttle the frequency of nfs_local_probe_async(),
otherwise there could be a flood of repeat calls to
nfs_local_probe_async().
The throttle is admin controlled using a new module parameter for
nfsv3, e.g.:
echo 512 > /sys/module/nfsv3/parameters/nfs3_localio_probe_throttle
Probe for NFSv3 LOCALIO every N IO requests (512 in this case). Must
be power-of-2, defaults to 0 (probing disabled).
On systems that expect to use LOCALIO with NFSv3 the admin should
configure the 'nfs3_localio_probe_throttle' module parameter.
This commit backfills module parameter documentation in localio.rst
Signed-off-by: Mike Snitzer <snitzer@kernel.org>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Anna Schumaker <anna.schumaker@oracle.com>
Also update Documentation/filesystems/nfs/localio.rst accordingly
and reduce the technical documentation debt that was previously
captured in that document.
Signed-off-by: Mike Snitzer <snitzer@kernel.org>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Acked-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Anna Schumaker <anna.schumaker@oracle.com>
This commit simply adds the required O_DIRECT plumbing. It doesn't
address the fact that NFS doesn't ensure all writes are page aligned
(nor device logical block size aligned as required by O_DIRECT).
Because NFS will read-modify-write for IO that isn't aligned, LOCALIO
will not use O_DIRECT semantics by default if/when an application
requests the use of O_DIRECT. Allow the use of O_DIRECT semantics by:
1: Adding a flag to the nfs_pgio_header struct to allow the NFS
O_DIRECT layer to signal that O_DIRECT was used by the application
2: Adding a 'localio_O_DIRECT_semantics' NFS module parameter that
when enabled will cause LOCALIO to use O_DIRECT semantics (this may
cause IO to fail if applications do not properly align their IO).
This commit is derived from code developed by Weston Andros Adamson.
Signed-off-by: Mike Snitzer <snitzer@kernel.org>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Anna Schumaker <anna.schumaker@oracle.com>
Benjamin Coddington <bcodding@redhat.com> says:
Last year both GFS2 and OCFS2 had some work done to make their locking more
robust when exported over NFS. Unfortunately, part of that work caused both
NLM (for NFS v3 exports) and kNFSD (for NFSv4.1+ exports) to no longer send
lock notifications to clients.
This in itself is not a huge problem because most NFS clients will still
poll the server in order to acquire a conflicted lock, but now that I've
noticed it I can't help but try to fix it because there are big advantages
for setups that might depend on timely lock notifications, and we've
supported that as a feature for a long time.
Its important for NLM and kNFSD that they do not block their kernel threads
inside filesystem's file_lock implementations because that can produce
deadlocks. We used to make sure of this by only trusting that
posix_lock_file() can correctly handle blocking lock calls asynchronously,
so the lock managers would only setup their file_lock requests for async
callbacks if the filesystem did not define its own lock() file operation.
However, when GFS2 and OCFS2 grew the capability to correctly
handle blocking lock requests asynchronously, they started signalling this
behavior with EXPORT_OP_ASYNC_LOCK, and the check for also trusting
posix_lock_file() was inadvertently dropped, so now most filesystems no
longer produce lock notifications when exported over NFS.
I tried to fix this by simply including the old check for lock(), but the
resulting include mess and layering violations was more than I could accept.
There's a much cleaner way presented here using an fop_flag, which while
potentially flag-greedy, greatly simplifies the problem and grooms the
way for future uses by both filesystems and lock managers alike.
* patches from https://lore.kernel.org/r/cover.1726083391.git.bcodding@redhat.com:
exportfs: Remove EXPORT_OP_ASYNC_LOCK
NLM/NFSD: Fix lock notifications for async-capable filesystems
gfs2/ocfs2: set FOP_ASYNC_LOCK
fs: Introduce FOP_ASYNC_LOCK
NFS: trace: show TIMEDOUT instead of 0x6e
nfsd: use system_unbound_wq for nfsd_file_gc_worker()
nfsd: count nfsd_file allocations
nfsd: fix refcount leak when file is unhashed after being found
nfsd: remove unneeded EEXIST error check in nfsd_do_file_acquire
nfsd: add list_head nf_gc to struct nfsd_file
Link: https://lore.kernel.org/r/cover.1726083391.git.bcodding@redhat.com
Signed-off-by: Christian Brauner <brauner@kernel.org>
This section answers a new FAQ entry:
9. How does LOCALIO make certain that object lifetimes are managed
properly given NFSD and NFS operate in different contexts?
See the detailed "NFS Client and Server Interlock" section below.
The first half of the section details NeilBrown's elegant design
for LOCALIO's nfs_uuid_t based interlock and is heavily based on
Neil's "net namespace refcounting" description here:
https://marc.info/?l=linux-nfs&m=172498546024767&w=2
The second half of the section details the per-cpu-refcount introduced
to ensure NFSD's nfsd_serv isn't destroyed while in use by a LOCALIO
client.
Signed-off-by: Mike Snitzer <snitzer@kernel.org>
Reviewed-by: NeilBrown <neilb@suse.de>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Anna Schumaker <anna.schumaker@oracle.com>
This document gives an overview of the LOCALIO auxiliary RPC protocol
added to the Linux NFS client and server to allow them to reliably
handshake to determine if they are on the same host.
Once an NFS client and server handshake as "local", the client will
bypass the network RPC protocol for read, write and commit operations.
Due to this XDR and RPC bypass, these operations will operate faster.
Signed-off-by: Mike Snitzer <snitzer@kernel.org>
Reviewed-by: NeilBrown <neilb@suse.de>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Anna Schumaker <anna.schumaker@oracle.com>
Pull vfs fanotify fsid updates from Christian Brauner:
"This work is part of the plan to enable fanotify to serve as a drop-in
replacement for inotify. While inotify is availabe on all filesystems,
fanotify currently isn't.
In order to support fanotify on all filesystems two things are needed:
(1) all filesystems need to support AT_HANDLE_FID
(2) all filesystems need to report a non-zero f_fsid
This contains (1) and allows filesystems to encode non-decodable file
handlers for fanotify without implementing any exportfs operations by
encoding a file id of type FILEID_INO64_GEN from i_ino and
i_generation.
Filesystems that want to opt out of encoding non-decodable file ids
for fanotify that don't support NFS export can do so by providing an
empty export_operations struct.
This also partially addresses (2) by generating f_fsid for simple
filesystems as well as freevxfs. Remaining filesystems will be dealt
with by separate patches.
Finally, this contains the patch from the current exportfs maintainers
which moves exportfs under vfs with Chuck, Jeff, and Amir as
maintainers and vfs.git as tree"
* tag 'vfs-6.7.fsid' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs:
MAINTAINERS: create an entry for exportfs
fs: fix build error with CONFIG_EXPORTFS=m or not defined
freevxfs: derive f_fsid from bdev->bd_dev
fs: report f_fsid from s_dev for "simple" filesystems
exportfs: support encoding non-decodeable file handles by default
exportfs: define FILEID_INO64_GEN* file handle types
exportfs: make ->encode_fh() a mandatory method for NFS export
exportfs: add helpers to check if filesystem can encode/decode file handles
Rename the default helper for encoding FILEID_INO32_GEN* file handles to
generic_encode_ino32_fh() and convert the filesystems that used the
default implementation to use the generic helper explicitly.
After this change, exportfs_encode_inode_fh() no longer has a default
implementation to encode FILEID_INO32_GEN* file handles.
This is a step towards allowing filesystems to encode non-decodeable
file handles for fanotify without having to implement any
export_operations.
Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Acked-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Link: https://lore.kernel.org/r/20231023180801.2953446-3-amir73il@gmail.com
Acked-by: Dave Kleikamp <dave.kleikamp@oracle.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Christian Brauner <brauner@kernel.org>
This patch reverts mostly commit 40595cdc93 ("nfs: block notification
on fs with its own ->lock") and introduces an EXPORT_OP_ASYNC_LOCK
export flag to signal that the "own ->lock" implementation supports
async lock requests. The only main user is DLM that is used by GFS2 and
OCFS2 filesystem. Those implement their own lock() implementation and
return FILE_LOCK_DEFERRED as return value. Since commit 40595cdc93
("nfs: block notification on fs with its own ->lock") the DLM
implementation were never updated. This patch should prepare for DLM
to set the EXPORT_OP_ASYNC_LOCK export flag and update the DLM
plock implementation regarding to it.
Acked-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Alexander Aring <aahringo@redhat.com>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Pull nfsd updates from Chuck Lever:
"I'm thrilled to announce that the Linux in-kernel NFS server now
offers NFSv4 write delegations. A write delegation enables a client to
cache data and metadata for a single file more aggressively, reducing
network round trips and server workload. Many thanks to Dai Ngo for
contributing this facility, and to Jeff Layton and Neil Brown for
reviewing and testing it.
This release also sees the removal of all support for DES- and
triple-DES-based Kerberos encryption types in the kernel's SunRPC
implementation. These encryption types have been deprecated by the
Internet community for years and are considered insecure. This change
affects both the in-kernel NFS client and server.
The server's UDP and TCP socket transports have now fully adopted
David Howells' new bio_vec iterator so that no more than one sendmsg()
call is needed to transmit each RPC message. In particular, this helps
kTLS optimize record boundaries when sending RPC-with-TLS replies, and
it takes the server a baby step closer to handling file I/O via
folios.
We've begun work on overhauling the SunRPC thread scheduler to remove
a costly linked-list walk when looking for an idle RPC service thread
to wake. The pre-requisites are included in this release. Thanks to
Neil Brown for his ongoing work on this improvement"
* tag 'nfsd-6.6' of git://git.kernel.org/pub/scm/linux/kernel/git/cel/linux: (56 commits)
Documentation: Add missing documentation for EXPORT_OP flags
SUNRPC: Remove unused declaration rpc_modcount()
SUNRPC: Remove unused declarations
NFSD: da_addr_body field missing in some GETDEVICEINFO replies
SUNRPC: Remove return value of svc_pool_wake_idle_thread()
SUNRPC: make rqst_should_sleep() idempotent()
SUNRPC: Clean up svc_set_num_threads
SUNRPC: Count ingress RPC messages per svc_pool
SUNRPC: Deduplicate thread wake-up code
SUNRPC: Move trace_svc_xprt_enqueue
SUNRPC: Add enum svc_auth_status
SUNRPC: change svc_xprt::xpt_flags bits to enum
SUNRPC: change svc_rqst::rq_flags bits to enum
SUNRPC: change svc_pool::sp_flags bits to enum
SUNRPC: change cache_head.flags bits to enum
SUNRPC: remove timeout arg from svc_recv()
SUNRPC: change svc_recv() to return void.
SUNRPC: call svc_process() from svc_recv().
nfsd: separate nfsd_last_thread() from nfsd_put()
nfsd: Simplify code around svc_exit_thread() call in nfsd()
...
The commits that introduced these flags neglected to update the
Documentation/filesystems/nfs/exporting.rst file.
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
So far, all callers of exportfs_encode_inode_fh(), except for fsnotify's
show_mark_fhandle(), check that filesystem can decode file handles, but
we would like to add more callers that do not require a file handle that
can be decoded.
Introduce a flag to explicitly request a file handle that may not to be
decoded later and a wrapper exportfs_encode_fid() that sets this flag
and convert show_mark_fhandle() to use the new wrapper.
This will be used to allow adding fanotify support to filesystems that
do not support NFS export.
Acked-by: Jeff Layton <jlayton@kernel.org>
Acked-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Message-Id: <20230502124817.3070545-3-amir73il@gmail.com>
