nfs4namespace.c

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/*
 * linux/fs/nfs/nfs4namespace.c
 *
 * Copyright (C) 2005 Trond Myklebust <[email protected]>
 * - Modified by David Howells <[email protected]>
 *
 * NFSv4 namespace
 */

#include <linux/dcache.h>
#include <linux/mount.h>
#include <linux/namei.h>
#include <linux/nfs_fs.h>
#include <linux/slab.h>
#include <linux/string.h>
#include <linux/sunrpc/clnt.h>
#include <linux/vfs.h>
#include <linux/inet.h>
#include "internal.h"
#include "nfs4_fs.h"
#include "dns_resolve.h"

#define NFSDBG_FACILITY     NFSDBG_VFS

/*
 * Convert the NFSv4 pathname components into a standard posix path.
 *
 * Note that the resulting string will be placed at the end of the buffer
 */
static inline char *nfs4_pathname_string(const struct nfs4_pathname *pathname,
                     char *buffer, ssize_t buflen)
{
    char *end = buffer + buflen;
    int n;

    *--end = '\0';
    buflen--;

    n = pathname->ncomponents;
    while (--n >= 0) {
        const struct nfs4_string *component = &pathname->components[n];
        buflen -= component->len + 1;
        if (buflen < 0)
            goto Elong;
        end -= component->len;
        memcpy(end, component->data, component->len);
        *--end = '/';
    }
    return end;
Elong:
    return ERR_PTR(-ENAMETOOLONG);
}

/*
 * return the path component of "<server>:<path>"
 *  nfspath - the "<server>:<path>" string
 *  end - one past the last char that could contain "<server>:"
 * returns NULL on failure
 */
static char *nfs_path_component(const char *nfspath, const char *end)
{
    char *p;

    if (*nfspath == '[') {
        /* parse [] escaped IPv6 addrs */
        p = strchr(nfspath, ']');
        if (p != NULL && ++p < end && *p == ':')
            return p + 1;
    } else {
        /* otherwise split on first colon */
        p = strchr(nfspath, ':');
        if (p != NULL && p < end)
            return p + 1;
    }
    return NULL;
}

/*
 * Determine the mount path as a string
 */
static char *nfs4_path(struct dentry *dentry, char *buffer, ssize_t buflen)
{
    char *limit;
    char *path = nfs_path(&limit, dentry, buffer, buflen,
                  NFS_PATH_CANONICAL);
    if (!IS_ERR(path)) {
        char *path_component = nfs_path_component(path, limit);
        if (path_component)
            return path_component;
    }
    return path;
}

/*
 * Check that fs_locations::fs_root [RFC3530 6.3] is a prefix for what we
 * believe to be the server path to this dentry
 */
static int nfs4_validate_fspath(struct dentry *dentry,
                const struct nfs4_fs_locations *locations,
                char *page, char *page2)
{
    const char *path, *fs_path;

    path = nfs4_path(dentry, page, PAGE_SIZE);
    if (IS_ERR(path))
        return PTR_ERR(path);

    fs_path = nfs4_pathname_string(&locations->fs_path, page2, PAGE_SIZE);
    if (IS_ERR(fs_path))
        return PTR_ERR(fs_path);

    if (strncmp(path, fs_path, strlen(fs_path)) != 0) {
        dprintk("%s: path %s does not begin with fsroot %s\n",
            __func__, path, fs_path);
        return -ENOENT;
    }

    return 0;
}

static size_t nfs_parse_server_name(char *string, size_t len,
        struct sockaddr *sa, size_t salen, struct nfs_server *server)
{
    struct net *net = rpc_net_ns(server->client);
    ssize_t ret;

    ret = rpc_pton(net, string, len, sa, salen);
    if (ret == 0) {
        ret = nfs_dns_resolve_name(net, string, len, sa, salen);
        if (ret < 0)
            ret = 0;
    }
    return ret;
}

rpc_authflavor_t nfs_find_best_sec(struct nfs4_secinfo_flavors *flavors)
{
    struct gss_api_mech *mech;
    struct xdr_netobj oid;
    int i;
    rpc_authflavor_t pseudoflavor = RPC_AUTH_UNIX;

    for (i = 0; i < flavors->num_flavors; i++) {
        struct nfs4_secinfo_flavor *flavor;
        flavor = &flavors->flavors[i];

        if (flavor->flavor == RPC_AUTH_NULL || flavor->flavor == RPC_AUTH_UNIX) {
            pseudoflavor = flavor->flavor;
            break;
        } else if (flavor->flavor == RPC_AUTH_GSS) {
            oid.len  = flavor->gss.sec_oid4.len;
            oid.data = flavor->gss.sec_oid4.data;
            mech = gss_mech_get_by_OID(&oid);
            if (!mech)
                continue;
            pseudoflavor = gss_svc_to_pseudoflavor(mech, flavor->gss.service);
            gss_mech_put(mech);
            break;
        }
    }

    return pseudoflavor;
}

static rpc_authflavor_t nfs4_negotiate_security(struct inode *inode, struct qstr *name)
{
    struct page *page;
    struct nfs4_secinfo_flavors *flavors;
    rpc_authflavor_t flavor;
    int err;

    page = alloc_page(GFP_KERNEL);
    if (!page)
        return -ENOMEM;
    flavors = page_address(page);

    err = nfs4_proc_secinfo(inode, name, flavors);
    if (err < 0) {
        flavor = err;
        goto out;
    }

    flavor = nfs_find_best_sec(flavors);

out:
    put_page(page);
    return flavor;
}

/*
 * Please call rpc_shutdown_client() when you are done with this client.
 */
struct rpc_clnt *nfs4_create_sec_client(struct rpc_clnt *clnt, struct inode *inode,
                    struct qstr *name)
{
    rpc_authflavor_t flavor;

    flavor = nfs4_negotiate_security(inode, name);
    if ((int)flavor < 0)
        return ERR_PTR((int)flavor);

    return rpc_clone_client_set_auth(clnt, flavor);
}

static struct vfsmount *try_location(struct nfs_clone_mount *mountdata,
                     char *page, char *page2,
                     const struct nfs4_fs_location *location)
{
    const size_t addr_bufsize = sizeof(struct sockaddr_storage);
    struct vfsmount *mnt = ERR_PTR(-ENOENT);
    char *mnt_path;
    unsigned int maxbuflen;
    unsigned int s;

    mnt_path = nfs4_pathname_string(&location->rootpath, page2, PAGE_SIZE);
    if (IS_ERR(mnt_path))
        return ERR_CAST(mnt_path);
    mountdata->mnt_path = mnt_path;
    maxbuflen = mnt_path - 1 - page2;

    mountdata->addr = kmalloc(addr_bufsize, GFP_KERNEL);
    if (mountdata->addr == NULL)
        return ERR_PTR(-ENOMEM);

    for (s = 0; s < location->nservers; s++) {
        const struct nfs4_string *buf = &location->servers[s];

        if (buf->len <= 0 || buf->len >= maxbuflen)
            continue;

        if (memchr(buf->data, IPV6_SCOPE_DELIMITER, buf->len))
            continue;

        mountdata->addrlen = nfs_parse_server_name(buf->data, buf->len,
                mountdata->addr, addr_bufsize,
                NFS_SB(mountdata->sb));
        if (mountdata->addrlen == 0)
            continue;

        rpc_set_port(mountdata->addr, NFS_PORT);

        memcpy(page2, buf->data, buf->len);
        page2[buf->len] = '\0';
        mountdata->hostname = page2;

        snprintf(page, PAGE_SIZE, "%s:%s",
                mountdata->hostname,
                mountdata->mnt_path);

        mnt = vfs_kern_mount(&nfs4_referral_fs_type, 0, page, mountdata);
        if (!IS_ERR(mnt))
            break;
    }
    kfree(mountdata->addr);
    return mnt;
}

static struct vfsmount *nfs_follow_referral(struct dentry *dentry,
                        const struct nfs4_fs_locations *locations)
{
    struct vfsmount *mnt = ERR_PTR(-ENOENT);
    struct nfs_clone_mount mountdata = {
        .sb = dentry->d_sb,
        .dentry = dentry,
        .authflavor = NFS_SB(dentry->d_sb)->client->cl_auth->au_flavor,
    };
    char *page = NULL, *page2 = NULL;
    int loc, error;

    if (locations == NULL || locations->nlocations <= 0)
        goto out;

    dprintk("%s: referral at %s/%s\n", __func__,
        dentry->d_parent->d_name.name, dentry->d_name.name);

    page = (char *) __get_free_page(GFP_USER);
    if (!page)
        goto out;

    page2 = (char *) __get_free_page(GFP_USER);
    if (!page2)
        goto out;

    /* Ensure fs path is a prefix of current dentry path */
    error = nfs4_validate_fspath(dentry, locations, page, page2);
    if (error < 0) {
        mnt = ERR_PTR(error);
        goto out;
    }

    for (loc = 0; loc < locations->nlocations; loc++) {
        const struct nfs4_fs_location *location = &locations->locations[loc];

        if (location == NULL || location->nservers <= 0 ||
            location->rootpath.ncomponents == 0)
            continue;

        mnt = try_location(&mountdata, page, page2, location);
        if (!IS_ERR(mnt))
            break;
    }

out:
    free_page((unsigned long) page);
    free_page((unsigned long) page2);
    dprintk("%s: done\n", __func__);
    return mnt;
}

/*
 * nfs_do_refmount - handle crossing a referral on server
 * @dentry - dentry of referral
 *
 */
static struct vfsmount *nfs_do_refmount(struct rpc_clnt *client, struct dentry *dentry)
{
    struct vfsmount *mnt = ERR_PTR(-ENOMEM);
    struct dentry *parent;
    struct nfs4_fs_locations *fs_locations = NULL;
    struct page *page;
    int err;

    /* BUG_ON(IS_ROOT(dentry)); */
    dprintk("%s: enter\n", __func__);

    page = alloc_page(GFP_KERNEL);
    if (page == NULL)
        goto out;

    fs_locations = kmalloc(sizeof(struct nfs4_fs_locations), GFP_KERNEL);
    if (fs_locations == NULL)
        goto out_free;

    /* Get locations */
    mnt = ERR_PTR(-ENOENT);

    parent = dget_parent(dentry);
    dprintk("%s: getting locations for %s/%s\n",
        __func__, parent->d_name.name, dentry->d_name.name);

    err = nfs4_proc_fs_locations(client, parent->d_inode, &dentry->d_name, fs_locations, page);
    dput(parent);
    if (err != 0 ||
        fs_locations->nlocations <= 0 ||
        fs_locations->fs_path.ncomponents <= 0)
        goto out_free;

    mnt = nfs_follow_referral(dentry, fs_locations);
out_free:
    __free_page(page);
    kfree(fs_locations);
out:
    dprintk("%s: done\n", __func__);
    return mnt;
}

struct vfsmount *nfs4_submount(struct nfs_server *server, struct dentry *dentry,
                   struct nfs_fh *fh, struct nfs_fattr *fattr)
{
    struct dentry *parent = dget_parent(dentry);
    struct rpc_clnt *client;
    struct vfsmount *mnt;

    /* Look it up again to get its attributes and sec flavor */
    client = nfs4_proc_lookup_mountpoint(parent->d_inode, &dentry->d_name, fh, fattr);
    dput(parent);
    if (IS_ERR(client))
        return ERR_CAST(client);

    if (fattr->valid & NFS_ATTR_FATTR_V4_REFERRAL)
        mnt = nfs_do_refmount(client, dentry);
    else
        mnt = nfs_do_submount(dentry, fh, fattr, client->cl_auth->au_flavor);

    rpc_shutdown_client(client);
    return mnt;
}