[PATCH 6/6] nfsd: add nfsd_file_acquire_local().

NeilBrown
2024-07-01T02:59:19Z

nfsd_file_acquire_local() can be used to look up a file by filehandle
without having a struct rqst. This can be used by NFS LOCALIO to allow
the NFS client to by the NFS protocol to directly access a file provided
by the NFS server which is running in the same kernel.

Signed-off-by: NeilBrown <neilb@suse.de>
---
fs/nfsd/filecache.c | 54 ++++++++++++++++++++++++++++++++++++++++-----
fs/nfsd/filecache.h | 4 ++++
fs/nfsd/nfsfh.c | 2 +-
fs/nfsd/nfsfh.h | 5 +++++
4 files changed, 59 insertions(+), 6 deletions(-)

diff --git a/fs/nfsd/filecache.c b/fs/nfsd/filecache.c
index ad9083ca144b..87f965d2574b 100644
--- a/fs/nfsd/filecache.c
+++ b/fs/nfsd/filecache.c
@@ -977,7 +977,10 @@ 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 nfsd_net *nn,
+ struct svc_cred *cred, int nfs_vers,
+ struct auth_domain *client,
+ struct svc_fh *fhp,
unsigned int may_flags, struct file *file,
struct nfsd_file **pnf, bool want_gc)
{
@@ -991,7 +994,7 @@ nfsd_file_do_acquire(struct svc_rqst *rqstp, struct svc_fh *fhp,
int ret;

retry:
- status = fh_verify(rqstp, fhp, S_IFREG,
+ status = __fh_verify(rqstp, nn, cred, nfs_vers, client, fhp, S_IFREG,
may_flags|NFSD_MAY_OWNER_OVERRIDE);
if (status != nfs_ok)
return status;
@@ -1139,7 +1142,8 @@ __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, NULL, NULL, 0, NULL,
+ fhp, may_flags, NULL, pnf, true);
}

/**
@@ -1163,7 +1167,46 @@ __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, NULL, NULL, 0, NULL, fhp,
+ may_flags, NULL, pnf, false);
+}
+
+/**
+ * nfsd_file_acquire_local - Get a struct nfsd_file with an open file for localio
+ * @nn: The nfsd network namespace in which to perform a lookup
+ * @cred: the user credential with which to validate access
+ * @nfs_vers: NFS version number to assume for request
+ * @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
+ * but not garbage-collected. The object is unhashed after the
+ * final nfsd_file_put().
+ *
+ * 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 nfsd_net *nn, struct svc_cred *cred,
+ int nfs_vers, struct auth_domain *client,
+ struct svc_fh *fhp,
+ unsigned int may_flags, struct nfsd_file **pnf)
+{
+ return nfsd_file_do_acquire(NULL, nn, cred, nfs_vers, client,
+ fhp, may_flags, NULL, pnf, false);
}

/**
@@ -1189,7 +1232,8 @@ 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, NULL, NULL, 0, NULL,
+ fhp, may_flags, file, pnf, false);
}

/*
diff --git a/fs/nfsd/filecache.h b/fs/nfsd/filecache.h
index c61884def906..d179dbae98e3 100644
--- a/fs/nfsd/filecache.h
+++ b/fs/nfsd/filecache.h
@@ -65,5 +65,9 @@ __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 nfsd_net *nn, struct svc_cred *cred,
+ int nfs_vers, 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 fb5a23060a4c..fa7e358d91ab 100644
--- a/fs/nfsd/nfsfh.c
+++ b/fs/nfsd/nfsfh.c
@@ -328,7 +328,7 @@ static __be32 nfsd_set_fh_dentry(struct svc_rqst *rqstp, struct nfsd_net *nn,
* @access is formed from the NFSD_MAY_* constants defined in
* fs/nfsd/vfs.h.
*/
-static __be32
+__be32
__fh_verify(struct svc_rqst *rqstp,
struct nfsd_net *nn, struct svc_cred *cred,
int nfs_vers, struct auth_domain *client,
diff --git a/fs/nfsd/nfsfh.h b/fs/nfsd/nfsfh.h
index 6ebdf7ea27bf..a2d9962f1bf8 100644
--- a/fs/nfsd/nfsfh.h
+++ b/fs/nfsd/nfsfh.h
@@ -214,7 +214,12 @@ extern char * SVCFH_fmt(struct svc_fh *fhp);
/*
* Function prototypes
*/
+struct nfsd_net;
__be32 fh_verify(struct svc_rqst *, struct svc_fh *, umode_t, int);
+__be32 __fh_verify(struct svc_rqst *rqstp,
+ struct nfsd_net *nn, struct svc_cred *cred,
+ int nfs_vers, struct auth_domain *client,
+ struct svc_fh *fhp, umode_t type, int access);
__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 *);
--
2.44.0