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linux/fs/nfsd/nfs3acl.c
Christian Brauner cac2f8b8d8
fs: rename current get acl method 
The current way of setting and getting posix acls through the generic
xattr interface is error prone and type unsafe. The vfs needs to
interpret and fixup posix acls before storing or reporting it to
userspace. Various hacks exist to make this work. The code is hard to
understand and difficult to maintain in it's current form. Instead of
making this work by hacking posix acls through xattr handlers we are
building a dedicated posix acl api around the get and set inode
operations. This removes a lot of hackiness and makes the codepaths
easier to maintain. A lot of background can be found in [1].

The current inode operation for getting posix acls takes an inode
argument but various filesystems (e.g., 9p, cifs, overlayfs) need access
to the dentry. In contrast to the ->set_acl() inode operation we cannot
simply extend ->get_acl() to take a dentry argument. The ->get_acl()
inode operation is called from:

acl_permission_check()
-> check_acl()
   -> get_acl()

which is part of generic_permission() which in turn is part of
inode_permission(). Both generic_permission() and inode_permission() are
called in the ->permission() handler of various filesystems (e.g.,
overlayfs). So simply passing a dentry argument to ->get_acl() would
amount to also having to pass a dentry argument to ->permission(). We
should avoid this unnecessary change.

So instead of extending the existing inode operation rename it from
->get_acl() to ->get_inode_acl() and add a ->get_acl() method later that
passes a dentry argument and which filesystems that need access to the
dentry can implement instead of ->get_inode_acl(). Filesystems like cifs
which allow setting and getting posix acls but not using them for
permission checking during lookup can simply not implement
->get_inode_acl().

This is intended to be a non-functional change.

Link: https://lore.kernel.org/all/20220801145520.1532837-1-brauner@kernel.org [1]
Suggested-by/Inspired-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
2022-10-20 10:13:27 +02:00

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// SPDX-License-Identifier: GPL-2.0
/*
* Process version 3 NFSACL requests.
*
* Copyright (C) 2002-2003 Andreas Gruenbacher <agruen@suse.de>
*/
#include "nfsd.h"
/* FIXME: nfsacl.h is a broken header */
#include <linux/nfsacl.h>
#include <linux/gfp.h>
#include "cache.h"
#include "xdr3.h"
#include "vfs.h"
/*
* NULL call.
*/
static __be32
nfsd3_proc_null(struct svc_rqst *rqstp)
{
return rpc_success;
}
/*
* Get the Access and/or Default ACL of a file.
*/
static __be32 nfsd3_proc_getacl(struct svc_rqst *rqstp)
{
struct nfsd3_getaclargs *argp = rqstp->rq_argp;
struct nfsd3_getaclres *resp = rqstp->rq_resp;
struct posix_acl *acl;
struct inode *inode;
svc_fh *fh;
fh = fh_copy(&resp->fh, &argp->fh);
resp->status = fh_verify(rqstp, &resp->fh, 0, NFSD_MAY_NOP);
if (resp->status != nfs_ok)
goto out;
inode = d_inode(fh->fh_dentry);
if (argp->mask & ~NFS_ACL_MASK) {
resp->status = nfserr_inval;
goto out;
}
resp->mask = argp->mask;
if (resp->mask & (NFS_ACL|NFS_ACLCNT)) {
acl = get_inode_acl(inode, ACL_TYPE_ACCESS);
if (acl == NULL) {
/* Solaris returns the inode's minimum ACL. */
acl = posix_acl_from_mode(inode->i_mode, GFP_KERNEL);
}
if (IS_ERR(acl)) {
resp->status = nfserrno(PTR_ERR(acl));
goto fail;
}
resp->acl_access = acl;
}
if (resp->mask & (NFS_DFACL|NFS_DFACLCNT)) {
/* Check how Solaris handles requests for the Default ACL
of a non-directory! */
acl = get_inode_acl(inode, ACL_TYPE_DEFAULT);
if (IS_ERR(acl)) {
resp->status = nfserrno(PTR_ERR(acl));
goto fail;
}
resp->acl_default = acl;
}
/* resp->acl_{access,default} are released in nfs3svc_release_getacl. */
out:
return rpc_success;
fail:
posix_acl_release(resp->acl_access);
posix_acl_release(resp->acl_default);
goto out;
}
/*
* Set the Access and/or Default ACL of a file.
*/
static __be32 nfsd3_proc_setacl(struct svc_rqst *rqstp)
{
struct nfsd3_setaclargs *argp = rqstp->rq_argp;
struct nfsd3_attrstat *resp = rqstp->rq_resp;
struct inode *inode;
svc_fh *fh;
int error;
fh = fh_copy(&resp->fh, &argp->fh);
resp->status = fh_verify(rqstp, &resp->fh, 0, NFSD_MAY_SATTR);
if (resp->status != nfs_ok)
goto out;
inode = d_inode(fh->fh_dentry);
error = fh_want_write(fh);
if (error)
goto out_errno;
inode_lock(inode);
error = set_posix_acl(&init_user_ns, fh->fh_dentry, ACL_TYPE_ACCESS,
argp->acl_access);
if (error)
goto out_drop_lock;
error = set_posix_acl(&init_user_ns, fh->fh_dentry, ACL_TYPE_DEFAULT,
argp->acl_default);
out_drop_lock:
inode_unlock(inode);
fh_drop_write(fh);
out_errno:
resp->status = nfserrno(error);
out:
/* argp->acl_{access,default} may have been allocated in
nfs3svc_decode_setaclargs. */
posix_acl_release(argp->acl_access);
posix_acl_release(argp->acl_default);
return rpc_success;
}
/*
* XDR decode functions
*/
static bool
nfs3svc_decode_getaclargs(struct svc_rqst *rqstp, struct xdr_stream *xdr)
{
struct nfsd3_getaclargs *args = rqstp->rq_argp;
if (!svcxdr_decode_nfs_fh3(xdr, &args->fh))
return false;
if (xdr_stream_decode_u32(xdr, &args->mask) < 0)
return false;
return true;
}
static bool
nfs3svc_decode_setaclargs(struct svc_rqst *rqstp, struct xdr_stream *xdr)
{
struct nfsd3_setaclargs *argp = rqstp->rq_argp;
if (!svcxdr_decode_nfs_fh3(xdr, &argp->fh))
return false;
if (xdr_stream_decode_u32(xdr, &argp->mask) < 0)
return false;
if (argp->mask & ~NFS_ACL_MASK)
return false;
if (!nfs_stream_decode_acl(xdr, NULL, (argp->mask & NFS_ACL) ?
&argp->acl_access : NULL))
return false;
if (!nfs_stream_decode_acl(xdr, NULL, (argp->mask & NFS_DFACL) ?
&argp->acl_default : NULL))
return false;
return true;
}
/*
* XDR encode functions
*/
/* GETACL */
static bool
nfs3svc_encode_getaclres(struct svc_rqst *rqstp, struct xdr_stream *xdr)
{
struct nfsd3_getaclres *resp = rqstp->rq_resp;
struct dentry *dentry = resp->fh.fh_dentry;
struct kvec *head = rqstp->rq_res.head;
struct inode *inode;
unsigned int base;
int n;
int w;
if (!svcxdr_encode_nfsstat3(xdr, resp->status))
return false;
switch (resp->status) {
case nfs_ok:
inode = d_inode(dentry);
if (!svcxdr_encode_post_op_attr(rqstp, xdr, &resp->fh))
return false;
if (xdr_stream_encode_u32(xdr, resp->mask) < 0)
return false;
base = (char *)xdr->p - (char *)head->iov_base;
rqstp->rq_res.page_len = w = nfsacl_size(
(resp->mask & NFS_ACL) ? resp->acl_access : NULL,
(resp->mask & NFS_DFACL) ? resp->acl_default : NULL);
while (w > 0) {
if (!*(rqstp->rq_next_page++))
return false;
w -= PAGE_SIZE;
}
n = nfsacl_encode(&rqstp->rq_res, base, inode,
resp->acl_access,
resp->mask & NFS_ACL, 0);
if (n > 0)
n = nfsacl_encode(&rqstp->rq_res, base + n, inode,
resp->acl_default,
resp->mask & NFS_DFACL,
NFS_ACL_DEFAULT);
if (n <= 0)
return false;
break;
default:
if (!svcxdr_encode_post_op_attr(rqstp, xdr, &resp->fh))
return false;
}
return true;
}
/* SETACL */
static bool
nfs3svc_encode_setaclres(struct svc_rqst *rqstp, struct xdr_stream *xdr)
{
struct nfsd3_attrstat *resp = rqstp->rq_resp;
return svcxdr_encode_nfsstat3(xdr, resp->status) &&
svcxdr_encode_post_op_attr(rqstp, xdr, &resp->fh);
}
/*
* XDR release functions
*/
static void nfs3svc_release_getacl(struct svc_rqst *rqstp)
{
struct nfsd3_getaclres *resp = rqstp->rq_resp;
fh_put(&resp->fh);
posix_acl_release(resp->acl_access);
posix_acl_release(resp->acl_default);
}
struct nfsd3_voidargs { int dummy; };
#define ST 1 /* status*/
#define AT 21 /* attributes */
#define pAT (1+AT) /* post attributes - conditional */
#define ACL (1+NFS_ACL_MAX_ENTRIES*3) /* Access Control List */
static const struct svc_procedure nfsd_acl_procedures3[3] = {
[ACLPROC3_NULL] = {
.pc_func = nfsd3_proc_null,
.pc_decode = nfssvc_decode_voidarg,
.pc_encode = nfssvc_encode_voidres,
.pc_argsize = sizeof(struct nfsd_voidargs),
.pc_argzero = sizeof(struct nfsd_voidargs),
.pc_ressize = sizeof(struct nfsd_voidres),
.pc_cachetype = RC_NOCACHE,
.pc_xdrressize = ST,
.pc_name = "NULL",
},
[ACLPROC3_GETACL] = {
.pc_func = nfsd3_proc_getacl,
.pc_decode = nfs3svc_decode_getaclargs,
.pc_encode = nfs3svc_encode_getaclres,
.pc_release = nfs3svc_release_getacl,
.pc_argsize = sizeof(struct nfsd3_getaclargs),
.pc_argzero = sizeof(struct nfsd3_getaclargs),
.pc_ressize = sizeof(struct nfsd3_getaclres),
.pc_cachetype = RC_NOCACHE,
.pc_xdrressize = ST+1+2*(1+ACL),
.pc_name = "GETACL",
},
[ACLPROC3_SETACL] = {
.pc_func = nfsd3_proc_setacl,
.pc_decode = nfs3svc_decode_setaclargs,
.pc_encode = nfs3svc_encode_setaclres,
.pc_release = nfs3svc_release_fhandle,
.pc_argsize = sizeof(struct nfsd3_setaclargs),
.pc_argzero = sizeof(struct nfsd3_setaclargs),
.pc_ressize = sizeof(struct nfsd3_attrstat),
.pc_cachetype = RC_NOCACHE,
.pc_xdrressize = ST+pAT,
.pc_name = "SETACL",
},
};
static unsigned int nfsd_acl_count3[ARRAY_SIZE(nfsd_acl_procedures3)];
const struct svc_version nfsd_acl_version3 = {
.vs_vers = 3,
.vs_nproc = 3,
.vs_proc = nfsd_acl_procedures3,
.vs_count = nfsd_acl_count3,
.vs_dispatch = nfsd_dispatch,
.vs_xdrsize = NFS3_SVC_XDRSIZE,
};
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