link.c

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/*
 *   fs/cifs/link.c
 *
 *   Copyright (C) International Business Machines  Corp., 2002,2008
 *   Author(s): Steve French ([email protected])
 *
 *   This library is free software; you can redistribute it and/or modify
 *   it under the terms of the GNU Lesser General Public License as published
 *   by the Free Software Foundation; either version 2.1 of the License, or
 *   (at your option) any later version.
 *
 *   This library is distributed in the hope that it will be useful,
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See
 *   the GNU Lesser General Public License for more details.
 *
 *   You should have received a copy of the GNU Lesser General Public License
 *   along with this library; if not, write to the Free Software
 *   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 */
#include <linux/fs.h>
#include <linux/stat.h>
#include <linux/slab.h>
#include <linux/namei.h>
#include "cifsfs.h"
#include "cifspdu.h"
#include "cifsglob.h"
#include "cifsproto.h"
#include "cifs_debug.h"
#include "cifs_fs_sb.h"

#define CIFS_MF_SYMLINK_LEN_OFFSET (4+1)
#define CIFS_MF_SYMLINK_MD5_OFFSET (CIFS_MF_SYMLINK_LEN_OFFSET+(4+1))
#define CIFS_MF_SYMLINK_LINK_OFFSET (CIFS_MF_SYMLINK_MD5_OFFSET+(32+1))
#define CIFS_MF_SYMLINK_LINK_MAXLEN (1024)
#define CIFS_MF_SYMLINK_FILE_SIZE \
    (CIFS_MF_SYMLINK_LINK_OFFSET + CIFS_MF_SYMLINK_LINK_MAXLEN)

#define CIFS_MF_SYMLINK_LEN_FORMAT "XSym\n%04u\n"
#define CIFS_MF_SYMLINK_MD5_FORMAT \
    "%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x\n"
#define CIFS_MF_SYMLINK_MD5_ARGS(md5_hash) \
    md5_hash[0],  md5_hash[1],  md5_hash[2],  md5_hash[3], \
    md5_hash[4],  md5_hash[5],  md5_hash[6],  md5_hash[7], \
    md5_hash[8],  md5_hash[9],  md5_hash[10], md5_hash[11],\
    md5_hash[12], md5_hash[13], md5_hash[14], md5_hash[15]

static int
symlink_hash(unsigned int link_len, const char *link_str, u8 *md5_hash)
{
    int rc;
    unsigned int size;
    struct crypto_shash *md5;
    struct sdesc *sdescmd5;

    md5 = crypto_alloc_shash("md5", 0, 0);
    if (IS_ERR(md5)) {
        rc = PTR_ERR(md5);
        cERROR(1, "%s: Crypto md5 allocation error %d", __func__, rc);
        return rc;
    }
    size = sizeof(struct shash_desc) + crypto_shash_descsize(md5);
    sdescmd5 = kmalloc(size, GFP_KERNEL);
    if (!sdescmd5) {
        rc = -ENOMEM;
        cERROR(1, "%s: Memory allocation failure", __func__);
        goto symlink_hash_err;
    }
    sdescmd5->shash.tfm = md5;
    sdescmd5->shash.flags = 0x0;

    rc = crypto_shash_init(&sdescmd5->shash);
    if (rc) {
        cERROR(1, "%s: Could not init md5 shash", __func__);
        goto symlink_hash_err;
    }
    rc = crypto_shash_update(&sdescmd5->shash, link_str, link_len);
    if (rc) {
        cERROR(1, "%s: Could not update iwth link_str", __func__);
        goto symlink_hash_err;
    }
    rc = crypto_shash_final(&sdescmd5->shash, md5_hash);
    if (rc)
        cERROR(1, "%s: Could not generate md5 hash", __func__);

symlink_hash_err:
    crypto_free_shash(md5);
    kfree(sdescmd5);

    return rc;
}

static int
CIFSParseMFSymlink(const u8 *buf,
           unsigned int buf_len,
           unsigned int *_link_len,
           char **_link_str)
{
    int rc;
    unsigned int link_len;
    const char *md5_str1;
    const char *link_str;
    u8 md5_hash[16];
    char md5_str2[34];

    if (buf_len != CIFS_MF_SYMLINK_FILE_SIZE)
        return -EINVAL;

    md5_str1 = (const char *)&buf[CIFS_MF_SYMLINK_MD5_OFFSET];
    link_str = (const char *)&buf[CIFS_MF_SYMLINK_LINK_OFFSET];

    rc = sscanf(buf, CIFS_MF_SYMLINK_LEN_FORMAT, &link_len);
    if (rc != 1)
        return -EINVAL;

    rc = symlink_hash(link_len, link_str, md5_hash);
    if (rc) {
        cFYI(1, "%s: MD5 hash failure: %d", __func__, rc);
        return rc;
    }

    snprintf(md5_str2, sizeof(md5_str2),
         CIFS_MF_SYMLINK_MD5_FORMAT,
         CIFS_MF_SYMLINK_MD5_ARGS(md5_hash));

    if (strncmp(md5_str1, md5_str2, 17) != 0)
        return -EINVAL;

    if (_link_str) {
        *_link_str = kstrndup(link_str, link_len, GFP_KERNEL);
        if (!*_link_str)
            return -ENOMEM;
    }

    *_link_len = link_len;
    return 0;
}

static int
CIFSFormatMFSymlink(u8 *buf, unsigned int buf_len, const char *link_str)
{
    int rc;
    unsigned int link_len;
    unsigned int ofs;
    u8 md5_hash[16];

    if (buf_len != CIFS_MF_SYMLINK_FILE_SIZE)
        return -EINVAL;

    link_len = strlen(link_str);

    if (link_len > CIFS_MF_SYMLINK_LINK_MAXLEN)
        return -ENAMETOOLONG;

    rc = symlink_hash(link_len, link_str, md5_hash);
    if (rc) {
        cFYI(1, "%s: MD5 hash failure: %d", __func__, rc);
        return rc;
    }

    snprintf(buf, buf_len,
         CIFS_MF_SYMLINK_LEN_FORMAT CIFS_MF_SYMLINK_MD5_FORMAT,
         link_len,
         CIFS_MF_SYMLINK_MD5_ARGS(md5_hash));

    ofs = CIFS_MF_SYMLINK_LINK_OFFSET;
    memcpy(buf + ofs, link_str, link_len);

    ofs += link_len;
    if (ofs < CIFS_MF_SYMLINK_FILE_SIZE) {
        buf[ofs] = '\n';
        ofs++;
    }

    while (ofs < CIFS_MF_SYMLINK_FILE_SIZE) {
        buf[ofs] = ' ';
        ofs++;
    }

    return 0;
}

static int
CIFSCreateMFSymLink(const unsigned int xid, struct cifs_tcon *tcon,
            const char *fromName, const char *toName,
            struct cifs_sb_info *cifs_sb)
{
    int rc;
    int oplock = 0;
    int remap;
    int create_options = CREATE_NOT_DIR;
    __u16 netfid = 0;
    u8 *buf;
    unsigned int bytes_written = 0;
    struct cifs_io_parms io_parms;
    struct nls_table *nls_codepage;

    nls_codepage = cifs_sb->local_nls;
    remap = cifs_sb->mnt_cifs_flags & CIFS_MOUNT_MAP_SPECIAL_CHR;

    buf = kmalloc(CIFS_MF_SYMLINK_FILE_SIZE, GFP_KERNEL);
    if (!buf)
        return -ENOMEM;

    rc = CIFSFormatMFSymlink(buf, CIFS_MF_SYMLINK_FILE_SIZE, toName);
    if (rc != 0) {
        kfree(buf);
        return rc;
    }

    if (backup_cred(cifs_sb))
        create_options |= CREATE_OPEN_BACKUP_INTENT;

    rc = CIFSSMBOpen(xid, tcon, fromName, FILE_CREATE, GENERIC_WRITE,
             create_options, &netfid, &oplock, NULL,
             nls_codepage, remap);
    if (rc != 0) {
        kfree(buf);
        return rc;
    }

    io_parms.netfid = netfid;
    io_parms.pid = current->tgid;
    io_parms.tcon = tcon;
    io_parms.offset = 0;
    io_parms.length = CIFS_MF_SYMLINK_FILE_SIZE;

    rc = CIFSSMBWrite(xid, &io_parms, &bytes_written, buf, NULL, 0);
    CIFSSMBClose(xid, tcon, netfid);
    kfree(buf);
    if (rc != 0)
        return rc;

    if (bytes_written != CIFS_MF_SYMLINK_FILE_SIZE)
        return -EIO;

    return 0;
}

static int
CIFSQueryMFSymLink(const unsigned int xid, struct cifs_tcon *tcon,
           const unsigned char *searchName, char **symlinkinfo,
           const struct nls_table *nls_codepage, int remap)
{
    int rc;
    int oplock = 0;
    __u16 netfid = 0;
    u8 *buf;
    char *pbuf;
    unsigned int bytes_read = 0;
    int buf_type = CIFS_NO_BUFFER;
    unsigned int link_len = 0;
    struct cifs_io_parms io_parms;
    FILE_ALL_INFO file_info;

    rc = CIFSSMBOpen(xid, tcon, searchName, FILE_OPEN, GENERIC_READ,
             CREATE_NOT_DIR, &netfid, &oplock, &file_info,
             nls_codepage, remap);
    if (rc != 0)
        return rc;

    if (file_info.EndOfFile != cpu_to_le64(CIFS_MF_SYMLINK_FILE_SIZE)) {
        CIFSSMBClose(xid, tcon, netfid);
        /* it's not a symlink */
        return -EINVAL;
    }

    buf = kmalloc(CIFS_MF_SYMLINK_FILE_SIZE, GFP_KERNEL);
    if (!buf)
        return -ENOMEM;
    pbuf = buf;
    io_parms.netfid = netfid;
    io_parms.pid = current->tgid;
    io_parms.tcon = tcon;
    io_parms.offset = 0;
    io_parms.length = CIFS_MF_SYMLINK_FILE_SIZE;

    rc = CIFSSMBRead(xid, &io_parms, &bytes_read, &pbuf, &buf_type);
    CIFSSMBClose(xid, tcon, netfid);
    if (rc != 0) {
        kfree(buf);
        return rc;
    }

    rc = CIFSParseMFSymlink(buf, bytes_read, &link_len, symlinkinfo);
    kfree(buf);
    if (rc != 0)
        return rc;

    return 0;
}

bool
CIFSCouldBeMFSymlink(const struct cifs_fattr *fattr)
{
    if (!(fattr->cf_mode & S_IFREG))
        /* it's not a symlink */
        return false;

    if (fattr->cf_eof != CIFS_MF_SYMLINK_FILE_SIZE)
        /* it's not a symlink */
        return false;

    return true;
}

int
CIFSCheckMFSymlink(struct cifs_fattr *fattr,
           const unsigned char *path,
           struct cifs_sb_info *cifs_sb, unsigned int xid)
{
    int rc;
    int oplock = 0;
    __u16 netfid = 0;
    struct tcon_link *tlink;
    struct cifs_tcon *pTcon;
    struct cifs_io_parms io_parms;
    u8 *buf;
    char *pbuf;
    unsigned int bytes_read = 0;
    int buf_type = CIFS_NO_BUFFER;
    unsigned int link_len = 0;
    FILE_ALL_INFO file_info;

    if (!CIFSCouldBeMFSymlink(fattr))
        /* it's not a symlink */
        return 0;

    tlink = cifs_sb_tlink(cifs_sb);
    if (IS_ERR(tlink))
        return PTR_ERR(tlink);
    pTcon = tlink_tcon(tlink);

    rc = CIFSSMBOpen(xid, pTcon, path, FILE_OPEN, GENERIC_READ,
             CREATE_NOT_DIR, &netfid, &oplock, &file_info,
             cifs_sb->local_nls,
             cifs_sb->mnt_cifs_flags &
                CIFS_MOUNT_MAP_SPECIAL_CHR);
    if (rc != 0)
        goto out;

    if (file_info.EndOfFile != cpu_to_le64(CIFS_MF_SYMLINK_FILE_SIZE)) {
        CIFSSMBClose(xid, pTcon, netfid);
        /* it's not a symlink */
        goto out;
    }

    buf = kmalloc(CIFS_MF_SYMLINK_FILE_SIZE, GFP_KERNEL);
    if (!buf) {
        rc = -ENOMEM;
        goto out;
    }
    pbuf = buf;
    io_parms.netfid = netfid;
    io_parms.pid = current->tgid;
    io_parms.tcon = pTcon;
    io_parms.offset = 0;
    io_parms.length = CIFS_MF_SYMLINK_FILE_SIZE;

    rc = CIFSSMBRead(xid, &io_parms, &bytes_read, &pbuf, &buf_type);
    CIFSSMBClose(xid, pTcon, netfid);
    if (rc != 0) {
        kfree(buf);
        goto out;
    }

    rc = CIFSParseMFSymlink(buf, bytes_read, &link_len, NULL);
    kfree(buf);
    if (rc == -EINVAL) {
        /* it's not a symlink */
        rc = 0;
        goto out;
    }

    if (rc != 0)
        goto out;

    /* it is a symlink */
    fattr->cf_eof = link_len;
    fattr->cf_mode &= ~S_IFMT;
    fattr->cf_mode |= S_IFLNK | S_IRWXU | S_IRWXG | S_IRWXO;
    fattr->cf_dtype = DT_LNK;
out:
    cifs_put_tlink(tlink);
    return rc;
}

int
cifs_hardlink(struct dentry *old_file, struct inode *inode,
          struct dentry *direntry)
{
    int rc = -EACCES;
    unsigned int xid;
    char *from_name = NULL;
    char *to_name = NULL;
    struct cifs_sb_info *cifs_sb = CIFS_SB(inode->i_sb);
    struct tcon_link *tlink;
    struct cifs_tcon *tcon;
    struct TCP_Server_Info *server;
    struct cifsInodeInfo *cifsInode;

    tlink = cifs_sb_tlink(cifs_sb);
    if (IS_ERR(tlink))
        return PTR_ERR(tlink);
    tcon = tlink_tcon(tlink);

    xid = get_xid();

    from_name = build_path_from_dentry(old_file);
    to_name = build_path_from_dentry(direntry);
    if ((from_name == NULL) || (to_name == NULL)) {
        rc = -ENOMEM;
        goto cifs_hl_exit;
    }

    if (tcon->unix_ext)
        rc = CIFSUnixCreateHardLink(xid, tcon, from_name, to_name,
                        cifs_sb->local_nls,
                        cifs_sb->mnt_cifs_flags &
                        CIFS_MOUNT_MAP_SPECIAL_CHR);
    else {
        server = tcon->ses->server;
        if (!server->ops->create_hardlink)
            return -ENOSYS;
        rc = server->ops->create_hardlink(xid, tcon, from_name, to_name,
                          cifs_sb);
        if ((rc == -EIO) || (rc == -EINVAL))
            rc = -EOPNOTSUPP;
    }

    d_drop(direntry);   /* force new lookup from server of target */

    /*
     * if source file is cached (oplocked) revalidate will not go to server
     * until the file is closed or oplock broken so update nlinks locally
     */
    if (old_file->d_inode) {
        cifsInode = CIFS_I(old_file->d_inode);
        if (rc == 0) {
            spin_lock(&old_file->d_inode->i_lock);
            inc_nlink(old_file->d_inode);
            spin_unlock(&old_file->d_inode->i_lock);
            /*
             * BB should we make this contingent on superblock flag
             * NOATIME?
             */
            /* old_file->d_inode->i_ctime = CURRENT_TIME; */
            /*
             * parent dir timestamps will update from srv within a
             * second, would it really be worth it to set the parent
             * dir cifs inode time to zero to force revalidate
             * (faster) for it too?
             */
        }
        /*
         * if not oplocked will force revalidate to get info on source
         * file from srv
         */
        cifsInode->time = 0;

        /*
         * Will update parent dir timestamps from srv within a second.
         * Would it really be worth it to set the parent dir (cifs
         * inode) time field to zero to force revalidate on parent
         * directory faster ie
         *
         * CIFS_I(inode)->time = 0;
         */
    }

cifs_hl_exit:
    kfree(from_name);
    kfree(to_name);
    free_xid(xid);
    cifs_put_tlink(tlink);
    return rc;
}

void *
cifs_follow_link(struct dentry *direntry, struct nameidata *nd)
{
    struct inode *inode = direntry->d_inode;
    int rc = -ENOMEM;
    unsigned int xid;
    char *full_path = NULL;
    char *target_path = NULL;
    struct cifs_sb_info *cifs_sb = CIFS_SB(inode->i_sb);
    struct tcon_link *tlink = NULL;
    struct cifs_tcon *tcon;

    xid = get_xid();

    tlink = cifs_sb_tlink(cifs_sb);
    if (IS_ERR(tlink)) {
        rc = PTR_ERR(tlink);
        tlink = NULL;
        goto out;
    }
    tcon = tlink_tcon(tlink);

    /*
     * For now, we just handle symlinks with unix extensions enabled.
     * Eventually we should handle NTFS reparse points, and MacOS
     * symlink support. For instance...
     *
     * rc = CIFSSMBQueryReparseLinkInfo(...)
     *
     * For now, just return -EACCES when the server doesn't support posix
     * extensions. Note that we still allow querying symlinks when posix
     * extensions are manually disabled. We could disable these as well
     * but there doesn't seem to be any harm in allowing the client to
     * read them.
     */
    if (!(cifs_sb->mnt_cifs_flags & CIFS_MOUNT_MF_SYMLINKS) &&
        !cap_unix(tcon->ses)) {
        rc = -EACCES;
        goto out;
    }

    full_path = build_path_from_dentry(direntry);
    if (!full_path)
        goto out;

    cFYI(1, "Full path: %s inode = 0x%p", full_path, inode);

    rc = -EACCES;
    /*
     * First try Minshall+French Symlinks, if configured
     * and fallback to UNIX Extensions Symlinks.
     */
    if (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_MF_SYMLINKS)
        rc = CIFSQueryMFSymLink(xid, tcon, full_path, &target_path,
                    cifs_sb->local_nls,
                    cifs_sb->mnt_cifs_flags &
                        CIFS_MOUNT_MAP_SPECIAL_CHR);

    if ((rc != 0) && cap_unix(tcon->ses))
        rc = CIFSSMBUnixQuerySymLink(xid, tcon, full_path, &target_path,
                         cifs_sb->local_nls);

    kfree(full_path);
out:
    if (rc != 0) {
        kfree(target_path);
        target_path = ERR_PTR(rc);
    }

    free_xid(xid);
    if (tlink)
        cifs_put_tlink(tlink);
    nd_set_link(nd, target_path);
    return NULL;
}

int
cifs_symlink(struct inode *inode, struct dentry *direntry, const char *symname)
{
    int rc = -EOPNOTSUPP;
    unsigned int xid;
    struct cifs_sb_info *cifs_sb = CIFS_SB(inode->i_sb);
    struct tcon_link *tlink;
    struct cifs_tcon *pTcon;
    char *full_path = NULL;
    struct inode *newinode = NULL;

    xid = get_xid();

    tlink = cifs_sb_tlink(cifs_sb);
    if (IS_ERR(tlink)) {
        rc = PTR_ERR(tlink);
        goto symlink_exit;
    }
    pTcon = tlink_tcon(tlink);

    full_path = build_path_from_dentry(direntry);
    if (full_path == NULL) {
        rc = -ENOMEM;
        goto symlink_exit;
    }

    cFYI(1, "Full path: %s", full_path);
    cFYI(1, "symname is %s", symname);

    /* BB what if DFS and this volume is on different share? BB */
    if (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_MF_SYMLINKS)
        rc = CIFSCreateMFSymLink(xid, pTcon, full_path, symname,
                    cifs_sb);
    else if (pTcon->unix_ext)
        rc = CIFSUnixCreateSymLink(xid, pTcon, full_path, symname,
                       cifs_sb->local_nls);
    /* else
       rc = CIFSCreateReparseSymLink(xid, pTcon, fromName, toName,
                    cifs_sb_target->local_nls); */

    if (rc == 0) {
        if (pTcon->unix_ext)
            rc = cifs_get_inode_info_unix(&newinode, full_path,
                              inode->i_sb, xid);
        else
            rc = cifs_get_inode_info(&newinode, full_path, NULL,
                         inode->i_sb, xid, NULL);

        if (rc != 0) {
            cFYI(1, "Create symlink ok, getinodeinfo fail rc = %d",
                  rc);
        } else {
            d_instantiate(direntry, newinode);
        }
    }
symlink_exit:
    kfree(full_path);
    cifs_put_tlink(tlink);
    free_xid(xid);
    return rc;
}

void cifs_put_link(struct dentry *direntry, struct nameidata *nd, void *cookie)
{
    char *p = nd_get_link(nd);
    if (!IS_ERR(p))
        kfree(p);
}