fs/ncpfs/symlink.c

   1 /*
   2  *  linux/fs/ncpfs/symlink.c
   3  *
   4  *  Code for allowing symbolic links on NCPFS (i.e. NetWare)
   5  *  Symbolic links are not supported on native NetWare, so we use an
   6  *  infrequently-used flag (Sh) and store a two-word magic header in
   7  *  the file to make sure we don't accidentally use a non-link file
   8  *  as a link.
   9  *
  10  *  When using the NFS namespace, we set the mode to indicate a symlink and
  11  *  don't bother with the magic numbers.
  12  *
  13  *  from linux/fs/ext2/symlink.c
  14  *
  15  *  Copyright (C) 1998-99, Frank A. Vorstenbosch
  16  *
  17  *  ncpfs symlink handling code
  18  *  NLS support (c) 1999 Petr Vandrovec
  19  *  Modified 2000 Ben Harris, University of Cambridge for NFS NS meta-info
  20  *
  21  */
  22
  23
  24 #include <asm/uaccess.h>
  25
  26 #include <linux/errno.h>
  27 #include <linux/fs.h>
  28 #include <linux/time.h>
  29 #include <linux/slab.h>
  30 #include <linux/mm.h>
  31 #include <linux/stat.h>
  32 #include "ncp_fs.h"
  33
  34 /* these magic numbers must appear in the symlink file -- this makes it a bit
  35    more resilient against the magic attributes being set on random files. */
  36
  37 #define NCP_SYMLINK_MAGIC0      cpu_to_le32(0x6c6d7973)     /* "symlnk->" */
  38 #define NCP_SYMLINK_MAGIC1      cpu_to_le32(0x3e2d6b6e)
  39
  40 /* ----- read a symbolic link ------------------------------------------ */
  41
  42 static int ncp_symlink_readpage(struct file *file, struct page *page)
  43 {
  44         struct inode *inode = page->mapping->host;
  45         int error, length, len;
  46         char *link, *rawlink;
  47         char *buf = kmap(page);
  48
  49         error = -ENOMEM;
  50         rawlink = kmalloc(NCP_MAX_SYMLINK_SIZE, GFP_KERNEL);
  51         if (!rawlink)
  52                 goto fail;
  53
  54         if (ncp_make_open(inode,O_RDONLY))
  55                 goto failEIO;
  56
  57         error=ncp_read_kernel(NCP_SERVER(inode),NCP_FINFO(inode)->file_handle,
  58                          0,NCP_MAX_SYMLINK_SIZE,rawlink,&length);
  59
  60         ncp_inode_close(inode);
  61         /* Close file handle if no other users... */
  62         ncp_make_closed(inode);
  63         if (error)
  64                 goto failEIO;
  65
  66         if (NCP_FINFO(inode)->flags & NCPI_KLUDGE_SYMLINK) {
  67                 if (length<NCP_MIN_SYMLINK_SIZE ||
  68                     ((__le32 *)rawlink)[0]!=NCP_SYMLINK_MAGIC0 ||
  69                     ((__le32 *)rawlink)[1]!=NCP_SYMLINK_MAGIC1)
  70                         goto failEIO;
  71                 link = rawlink + 8;
  72                 length -= 8;
  73         } else {
  74                 link = rawlink;
  75         }
  76
  77         len = NCP_MAX_SYMLINK_SIZE;
  78         error = ncp_vol2io(NCP_SERVER(inode), buf, &len, link, length, 0);
  79         kfree(rawlink);
  80         if (error)
  81                 goto fail;
  82         SetPageUptodate(page);
  83         kunmap(page);
  84         unlock_page(page);
  85         return 0;
  86
  87 failEIO:
  88         error = -EIO;
  89         kfree(rawlink);
  90 fail:
  91         SetPageError(page);
  92         kunmap(page);
  93         unlock_page(page);
  94         return error;
  95 }
  96
  97 /*
  98  * symlinks can't do much...
  99  */
 100 const struct address_space_operations ncp_symlink_aops = {
 101         .readpage       = ncp_symlink_readpage,
 102 };
 103
 104 /* ----- create a new symbolic link -------------------------------------- */
 105
 106 int ncp_symlink(struct inode *dir, struct dentry *dentry, const char *symname) {
 107         struct inode *inode;
 108         char *rawlink;
 109         int length, err, i, outlen;
 110         int kludge;
 111         int mode;
 112         __le32 attr;
 113         unsigned int hdr;
 114
 115         DPRINTK("ncp_symlink(dir=%p,dentry=%p,symname=%s)\n",dir,dentry,symname);
 116
 117         if (ncp_is_nfs_extras(NCP_SERVER(dir), NCP_FINFO(dir)->volNumber))
 118                 kludge = 0;
 119         else
 120 #ifdef CONFIG_NCPFS_EXTRAS
 121         if (NCP_SERVER(dir)->m.flags & NCP_MOUNT_SYMLINKS)
 122                 kludge = 1;
 123         else
 124 #endif
 125         /* EPERM is returned by VFS if symlink procedure does not exist */
 126                 return -EPERM;
 127
 128         rawlink = kmalloc(NCP_MAX_SYMLINK_SIZE, GFP_KERNEL);
 129         if (!rawlink)
 130                 return -ENOMEM;
 131
 132         if (kludge) {
 133                 mode = 0;
 134                 attr = aSHARED | aHIDDEN;
 135                 ((__le32 *)rawlink)[0]=NCP_SYMLINK_MAGIC0;
 136                 ((__le32 *)rawlink)[1]=NCP_SYMLINK_MAGIC1;
 137                 hdr = 8;
 138         } else {
 139                 mode = S_IFLNK | S_IRWXUGO;
 140                 attr = 0;
 141                 hdr = 0;
 142         }
 143
 144         length = strlen(symname);
 145         /* map to/from server charset, do not touch upper/lower case as
 146            symlink can point out of ncp filesystem */
 147         outlen = NCP_MAX_SYMLINK_SIZE - hdr;
 148         err = ncp_io2vol(NCP_SERVER(dir), rawlink + hdr, &outlen, symname, length, 0);
 149         if (err)
 150                 goto failfree;
 151
 152         outlen += hdr;
 153
 154         err = -EIO;
 155         if (ncp_create_new(dir,dentry,mode,0,attr)) {
 156                 goto failfree;
 157         }
 158
 159         inode=dentry->d_inode;
 160
 161         if (ncp_make_open(inode, O_WRONLY))
 162                 goto failfree;
 163
 164         if (ncp_write_kernel(NCP_SERVER(inode), NCP_FINFO(inode)->file_handle,
 165                              0, outlen, rawlink, &i) || i!=outlen) {
 166                 goto fail;
 167         }
 168
 169         ncp_inode_close(inode);
 170         ncp_make_closed(inode);
 171         kfree(rawlink);
 172         return 0;
 173 fail:;
 174         ncp_inode_close(inode);
 175         ncp_make_closed(inode);
 176 failfree:;
 177         kfree(rawlink);
 178         return err;
 179 }
 180
 181 /* ----- EOF ----- */