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Message-ID: <CAN-5tyFFx+_WnLbHq0bLH0uQ7XkK=wh2urooqvauTW-hxxz7cw@mail.gmail.com>
Date: Thu, 23 Oct 2025 10:15:42 -0400
From: Olga Kornievskaia <aglo@...ch.edu>
To: Jeff Layton <jlayton@...nel.org>
Cc: Chuck Lever <chuck.lever@...cle.com>, NeilBrown <neil@...wn.name>,
Olga Kornievskaia <okorniev@...hat.com>, Dai Ngo <Dai.Ngo@...cle.com>, Tom Talpey <tom@...pey.com>,
Trond Myklebust <trondmy@...nel.org>, Anna Schumaker <anna@...nel.org>, Mike Snitzer <snitzer@...nel.org>,
linux-nfs@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] lockd: don't allow locking on reexported NFSv2/3
On Thu, Oct 23, 2025 at 9:13 AM Jeff Layton <jlayton@...nel.org> wrote:
>
> Since commit 9254c8ae9b81 ("nfsd: disallow file locking and delegations
> for NFSv4 reexport"), file locking when reexporting an NFS mount via
> NFSv4 is expressly prohibited by nfsd. Do the same in lockd:
>
> Add a new nlmsvc_file_cannot_lock() helper that will test whether file
> locking is allowed for a given file, and return nlm_lck_denied_nolocks
> if it isn't.
>
> Signed-off-by: Jeff Layton <jlayton@...nel.org>
Tested-by: Olga Kornievskaia <okorniev@...hat.com>
> ---
> Regardless of how we fix the bug that Olga found recently, I think we
> need to do this as well. We don't allow locking when reexporting via v4,
> and I don't think we want to allow it when reexporting via v2/3 either.
> ---
> fs/lockd/svclock.c | 12 ++++++++++++
> fs/lockd/svcshare.c | 6 ++++++
> include/linux/lockd/lockd.h | 9 ++++++++-
> 3 files changed, 26 insertions(+), 1 deletion(-)
>
> diff --git a/fs/lockd/svclock.c b/fs/lockd/svclock.c
> index c1315df4b350bbd753305b5c08550d50f67b92aa..cd42e480a7000f1b3ec7fca5ecc7fb8dc4755a09 100644
> --- a/fs/lockd/svclock.c
> +++ b/fs/lockd/svclock.c
> @@ -495,6 +495,9 @@ nlmsvc_lock(struct svc_rqst *rqstp, struct nlm_file *file,
> (long long)lock->fl.fl_end,
> wait);
>
> + if (nlmsvc_file_cannot_lock(file))
> + return nlm_lck_denied_nolocks;
> +
> if (!locks_can_async_lock(nlmsvc_file_file(file)->f_op)) {
> async_block = wait;
> wait = 0;
> @@ -621,6 +624,9 @@ nlmsvc_testlock(struct svc_rqst *rqstp, struct nlm_file *file,
> (long long)lock->fl.fl_start,
> (long long)lock->fl.fl_end);
>
> + if (nlmsvc_file_cannot_lock(file))
> + return nlm_lck_denied_nolocks;
> +
> if (locks_in_grace(SVC_NET(rqstp))) {
> ret = nlm_lck_denied_grace_period;
> goto out;
> @@ -678,6 +684,9 @@ nlmsvc_unlock(struct net *net, struct nlm_file *file, struct nlm_lock *lock)
> (long long)lock->fl.fl_start,
> (long long)lock->fl.fl_end);
>
> + if (nlmsvc_file_cannot_lock(file))
> + return nlm_lck_denied_nolocks;
> +
> /* First, cancel any lock that might be there */
> nlmsvc_cancel_blocked(net, file, lock);
>
> @@ -715,6 +724,9 @@ nlmsvc_cancel_blocked(struct net *net, struct nlm_file *file, struct nlm_lock *l
> (long long)lock->fl.fl_start,
> (long long)lock->fl.fl_end);
>
> + if (nlmsvc_file_cannot_lock(file))
> + return nlm_lck_denied_nolocks;
> +
> if (locks_in_grace(net))
> return nlm_lck_denied_grace_period;
>
> diff --git a/fs/lockd/svcshare.c b/fs/lockd/svcshare.c
> index ade4931b2da247abd23bd16923f1d2388dc6ce00..88c81ce1148d92bd29ec580ac399ac944ba5ecf8 100644
> --- a/fs/lockd/svcshare.c
> +++ b/fs/lockd/svcshare.c
> @@ -32,6 +32,9 @@ nlmsvc_share_file(struct nlm_host *host, struct nlm_file *file,
> struct xdr_netobj *oh = &argp->lock.oh;
> u8 *ohdata;
>
> + if (nlmsvc_file_cannot_lock(file))
> + return nlm_lck_denied_nolocks;
> +
> for (share = file->f_shares; share; share = share->s_next) {
> if (share->s_host == host && nlm_cmp_owner(share, oh))
> goto update;
> @@ -72,6 +75,9 @@ nlmsvc_unshare_file(struct nlm_host *host, struct nlm_file *file,
> struct nlm_share *share, **shpp;
> struct xdr_netobj *oh = &argp->lock.oh;
>
> + if (nlmsvc_file_cannot_lock(file))
> + return nlm_lck_denied_nolocks;
> +
> for (shpp = &file->f_shares; (share = *shpp) != NULL;
> shpp = &share->s_next) {
> if (share->s_host == host && nlm_cmp_owner(share, oh)) {
> diff --git a/include/linux/lockd/lockd.h b/include/linux/lockd/lockd.h
> index c8f0f9458f2cc035fd9161f8f2486ba76084abf1..330e38776bb20d09c20697fc38a96c161ad0313a 100644
> --- a/include/linux/lockd/lockd.h
> +++ b/include/linux/lockd/lockd.h
> @@ -12,6 +12,7 @@
>
> /* XXX: a lot of this should really be under fs/lockd. */
>
> +#include <linux/exportfs.h>
> #include <linux/in.h>
> #include <linux/in6.h>
> #include <net/ipv6.h>
> @@ -307,7 +308,7 @@ void nlmsvc_invalidate_all(void);
> int nlmsvc_unlock_all_by_sb(struct super_block *sb);
> int nlmsvc_unlock_all_by_ip(struct sockaddr *server_addr);
>
> -static inline struct file *nlmsvc_file_file(struct nlm_file *file)
> +static inline struct file *nlmsvc_file_file(const struct nlm_file *file)
> {
> return file->f_file[O_RDONLY] ?
> file->f_file[O_RDONLY] : file->f_file[O_WRONLY];
> @@ -318,6 +319,12 @@ static inline struct inode *nlmsvc_file_inode(struct nlm_file *file)
> return file_inode(nlmsvc_file_file(file));
> }
>
> +static inline bool
> +nlmsvc_file_cannot_lock(const struct nlm_file *file)
> +{
> + return exportfs_cannot_lock(nlmsvc_file_file(file)->f_path.dentry->d_sb->s_export_op);
> +}
> +
> static inline int __nlm_privileged_request4(const struct sockaddr *sap)
> {
> const struct sockaddr_in *sin = (struct sockaddr_in *)sap;
>
> ---
> base-commit: 316f960d9ffb8439e0876dc2eab812e55f3ccb2a
> change-id: 20251023-lockd-owner-a529e45d8622
>
> Best regards,
> --
> Jeff Layton <jlayton@...nel.org>
>
>
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