On Wed, 2024-08-28 at 21:04 -0400, Mike Snitzer wrote:
> From: NeilBrown <neilb@xxxxxxx>
>
> nfsd_file_acquire_local() can be used to look up a file by filehandle
> without having a struct svc_rqst. This can be used by NFS LOCALIO to
> allow the NFS client to bypass the NFS protocol to directly access a
> file provided by the NFS server which is running in the same kernel.
>
> In nfsd_file_do_acquire() care is taken to always use fh_verify() if
> rqstp is not NULL (as is the case for non-LOCALIO callers). Otherwise
> the non-LOCALIO callers will not supply the correct and required
> arguments to __fh_verify (e.g. gssclient isn't passed).
>
> Introduce fh_verify_local() wrapper around __fh_verify to make it
> clear that LOCALIO is intended caller.
>
> Also, use GC for nfsd_file returned by nfsd_file_acquire_local. GC
> offers performance improvements if/when a file is reopened before
> launderette cleans it from the filecache's LRU.
>
> Suggested-by: Jeff Layton <jlayton@xxxxxxxxxx> # use filecache's GC
> Signed-off-by: NeilBrown <neilb@xxxxxxx>
> Co-developed-by: Mike Snitzer <snitzer@xxxxxxxxxx>
> Signed-off-by: Mike Snitzer <snitzer@xxxxxxxxxx>
> Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
> ---
> fs/nfsd/filecache.c | 71 ++++++++++++++++++++++++++++++++++++++++-----
> fs/nfsd/filecache.h | 3 ++
> fs/nfsd/nfsfh.c | 39 +++++++++++++++++++++++++
> fs/nfsd/nfsfh.h | 2 ++
> 4 files changed, 108 insertions(+), 7 deletions(-)
>
> diff --git a/fs/nfsd/filecache.c b/fs/nfsd/filecache.c
> index 9e9d246f993c..2dc72de31f61 100644
> --- a/fs/nfsd/filecache.c
> +++ b/fs/nfsd/filecache.c
> @@ -982,12 +982,14 @@ nfsd_file_is_cached(struct inode *inode)
> }
>
> static __be32
> -nfsd_file_do_acquire(struct svc_rqst *rqstp, struct svc_fh *fhp,
> +nfsd_file_do_acquire(struct svc_rqst *rqstp, struct net *net,
> + struct svc_cred *cred,
> + struct auth_domain *client,
> + struct svc_fh *fhp,
> unsigned int may_flags, struct file *file,
> struct nfsd_file **pnf, bool want_gc)
> {
> unsigned char need = may_flags & NFSD_FILE_MAY_MASK;
> - struct net *net = SVC_NET(rqstp);
> struct nfsd_file *new, *nf;
> bool stale_retry = true;
> bool open_retry = true;
> @@ -996,8 +998,13 @@ nfsd_file_do_acquire(struct svc_rqst *rqstp, struct svc_fh *fhp,
> int ret;
>
> retry:
> - status = fh_verify(rqstp, fhp, S_IFREG,
> - may_flags|NFSD_MAY_OWNER_OVERRIDE);
> + if (rqstp) {
> + status = fh_verify(rqstp, fhp, S_IFREG,
> + may_flags|NFSD_MAY_OWNER_OVERRIDE);
> + } else {
> + status = fh_verify_local(net, cred, client, fhp, S_IFREG,
> + may_flags|NFSD_MAY_OWNER_OVERRIDE);
> + }
> if (status != nfs_ok)
> return status;
> inode = d_inode(fhp->fh_dentry);
> @@ -1143,7 +1150,8 @@ __be32
> nfsd_file_acquire_gc(struct svc_rqst *rqstp, struct svc_fh *fhp,
> unsigned int may_flags, struct nfsd_file **pnf)
> {
> - return nfsd_file_do_acquire(rqstp, fhp, may_flags, NULL, pnf, true);
> + return nfsd_file_do_acquire(rqstp, SVC_NET(rqstp), NULL, NULL,
> + fhp, may_flags, NULL, pnf, true);
> }
>
> /**
> @@ -1167,7 +1175,55 @@ __be32
> nfsd_file_acquire(struct svc_rqst *rqstp, struct svc_fh *fhp,
> unsigned int may_flags, struct nfsd_file **pnf)
> {
> - return nfsd_file_do_acquire(rqstp, fhp, may_flags, NULL, pnf, false);
> + return nfsd_file_do_acquire(rqstp, SVC_NET(rqstp), NULL, NULL,
> + fhp, may_flags, NULL, pnf, false);
> +}
> +
> +/**
> + * nfsd_file_acquire_local - Get a struct nfsd_file with an open file for localio
> + * @net: The network namespace in which to perform a lookup
> + * @cred: the user credential with which to validate access
> + * @client: the auth_domain for LOCALIO lookup
> + * @fhp: the NFS filehandle of the file to be opened
> + * @may_flags: NFSD_MAY_ settings for the file
> + * @pnf: OUT: new or found "struct nfsd_file" object
> + *
> + * This file lookup interface provide access to a file given the
> + * filehandle and credential. No connection-based authorisation
> + * is performed and in that way it is quite different to other
> + * file access mediated by nfsd. It allows a kernel module such as the NFS
> + * client to reach across network and filesystem namespaces to access
> + * a file. The security implications of this should be carefully
> + * considered before use.
> + *
> + * The nfsd_file object returned by this API is reference-counted
> + * and garbage-collected. The object is retained for a few
> + * seconds after the final nfsd_file_put() in case the caller
> + * wants to re-use it.
> + *
> + * Return values:
> + * %nfs_ok - @pnf points to an nfsd_file with its reference
> + * count boosted.
> + *
> + * On error, an nfsstat value in network byte order is returned.
> + */
> +__be32
> +nfsd_file_acquire_local(struct net *net, struct svc_cred *cred,
> + struct auth_domain *client, struct svc_fh *fhp,
> + unsigned int may_flags, struct nfsd_file **pnf)
> +{
> + /*
> + * Save creds before calling nfsd_file_do_acquire() (which calls
> + * nfsd_setuser). Important because caller (LOCALIO) is from
> + * client context.
> + */
> + const struct cred *save_cred = get_current_cred();
> + __be32 beres;
> +
> + beres = nfsd_file_do_acquire(NULL, net, cred, client,
> + fhp, may_flags, NULL, pnf, true);
> + revert_creds(save_cred);
> + return beres;
> }
>
> /**
> @@ -1193,7 +1249,8 @@ nfsd_file_acquire_opened(struct svc_rqst *rqstp, struct svc_fh *fhp,
> unsigned int may_flags, struct file *file,
> struct nfsd_file **pnf)
> {
> - return nfsd_file_do_acquire(rqstp, fhp, may_flags, file, pnf, false);
> + return nfsd_file_do_acquire(rqstp, SVC_NET(rqstp), NULL, NULL,
> + fhp, may_flags, file, pnf, false);
> }
>
> /*
> diff --git a/fs/nfsd/filecache.h b/fs/nfsd/filecache.h
> index 3fbec24eea6c..26ada78b8c1e 100644
> --- a/fs/nfsd/filecache.h
> +++ b/fs/nfsd/filecache.h
> @@ -66,5 +66,8 @@ __be32 nfsd_file_acquire(struct svc_rqst *rqstp, struct svc_fh *fhp,
> __be32 nfsd_file_acquire_opened(struct svc_rqst *rqstp, struct svc_fh *fhp,
> unsigned int may_flags, struct file *file,
> struct nfsd_file **nfp);
> +__be32 nfsd_file_acquire_local(struct net *net, struct svc_cred *cred,
> + struct auth_domain *client, struct svc_fh *fhp,
> + unsigned int may_flags, struct nfsd_file **pnf);
> int nfsd_file_cache_stats_show(struct seq_file *m, void *v);
> #endif /* _FS_NFSD_FILECACHE_H */
> diff --git a/fs/nfsd/nfsfh.c b/fs/nfsd/nfsfh.c
> index 80c06e170e9a..49468e478d23 100644
> --- a/fs/nfsd/nfsfh.c
> +++ b/fs/nfsd/nfsfh.c
> @@ -301,6 +301,22 @@ static __be32 nfsd_set_fh_dentry(struct svc_rqst *rqstp, struct net *net,
> return error;
> }
>
> +/**
> + * __fh_verify - filehandle lookup and access checking
> + * @rqstp: RPC transaction context, or NULL
> + * @net: net namespace in which to perform the export lookup
> + * @cred: RPC user credential
> + * @client: RPC auth domain
> + * @gssclient: RPC GSS auth domain, or NULL
> + * @fhp: filehandle to be verified
> + * @type: expected type of object pointed to by filehandle
> + * @access: type of access needed to object
> + *
> + * This internal API can be used by callers who do not have an RPC
> + * transaction context (ie are not running in an nfsd thread).
> + *
> + * See fh_verify() for further descriptions of @fhp, @type, and @access.
> + */
> static __be32
> __fh_verify(struct svc_rqst *rqstp,
> struct net *net, struct svc_cred *cred,
> @@ -382,6 +398,29 @@ __fh_verify(struct svc_rqst *rqstp,
> return error;
> }
>
> +/**
> + * fh_verify_local - filehandle lookup and access checking
> + * @net: net namespace in which to perform the export lookup
> + * @cred: RPC user credential
> + * @client: RPC auth domain
> + * @fhp: filehandle to be verified
> + * @type: expected type of object pointed to by filehandle
> + * @access: type of access needed to object
> + *
> + * This API can be used by callers who do not have an RPC
> + * transaction context (ie are not running in an nfsd thread).
> + *
> + * See fh_verify() for further descriptions of @fhp, @type, and @access.
> + */
> +__be32
> +fh_verify_local(struct net *net, struct svc_cred *cred,
> + struct auth_domain *client, struct svc_fh *fhp,
> + umode_t type, int access)
> +{
> + return __fh_verify(NULL, net, cred, client, NULL,
> + fhp, type, access);
> +}
> +
> /**
> * fh_verify - filehandle lookup and access checking
> * @rqstp: pointer to current rpc request
> diff --git a/fs/nfsd/nfsfh.h b/fs/nfsd/nfsfh.h
> index 8d46e203d139..5b7394801dc4 100644
> --- a/fs/nfsd/nfsfh.h
> +++ b/fs/nfsd/nfsfh.h
> @@ -217,6 +217,8 @@ extern char * SVCFH_fmt(struct svc_fh *fhp);
> * Function prototypes
> */
> __be32 fh_verify(struct svc_rqst *, struct svc_fh *, umode_t, int);
> +__be32 fh_verify_local(struct net *, struct svc_cred *, struct auth_domain *,
> + struct svc_fh *, umode_t, int);
> __be32 fh_compose(struct svc_fh *, struct svc_export *, struct dentry *, struct svc_fh *);
> __be32 fh_update(struct svc_fh *);
> void fh_put(struct svc_fh *);
Reviewed-by: Jeff Layton <jlayton@xxxxxxxxxx>
