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  *  from linux/fs/ext2/symlink.c
  11  *
  12  *  Copyright (C) 1998-99, Frank A. Vorstenbosch
  13  *
  14  *  ncpfs symlink handling code
  15  *  NLS support (c) 1999 Petr Vandrovec
  16  *
  17  */
  18
  19 #include <linux/config.h>
  20
  21 #ifdef CONFIG_NCPFS_EXTRAS
  22
  23 #include <asm/uaccess.h>
  24 #include <asm/segment.h>
  25
  26 #include <linux/errno.h>
  27 #include <linux/fs.h>
  28 #include <linux/ncp_fs.h>
  29 #include <linux/sched.h>
  30 #include <linux/mm.h>
  31 #include <linux/stat.h>
  32 #include "ncplib_kernel.h"
  33
  34
  35 /* these magic numbers must appear in the symlink file -- this makes it a bit
  36    more resilient against the magic attributes being set on random files. */
  37
  38 #define NCP_SYMLINK_MAGIC0      le32_to_cpu(0x6c6d7973)     /* "symlnk->" */
  39 #define NCP_SYMLINK_MAGIC1      le32_to_cpu(0x3e2d6b6e)
  40
  41 static int ncp_readlink(struct dentry *, char *, int);
  42 static struct dentry *ncp_follow_link(struct dentry *, struct dentry *, unsigned int);
  43 int ncp_create_new(struct inode *dir, struct dentry *dentry,
  44                           int mode,int attributes);
  45
  46 /*
  47  * symlinks can't do much...
  48  */
  49 struct inode_operations ncp_symlink_inode_operations={
  50         NULL,                   /* no file-operations */
  51         NULL,                   /* create */
  52         NULL,                   /* lookup */
  53         NULL,                   /* link */
  54         NULL,                   /* unlink */
  55         NULL,                   /* symlink */
  56         NULL,                   /* mkdir */
  57         NULL,                   /* rmdir */
  58         NULL,                   /* mknod */
  59         NULL,                   /* rename */
  60         ncp_readlink,           /* readlink */
  61         ncp_follow_link,        /* follow_link */
  62         NULL,                   /* get_block */
  63         NULL,                   /* readpage */
  64         NULL,                   /* writepage */
  65         NULL,                   /* truncate */
  66         NULL,                   /* permission */
  67         NULL                    /* revalidate */
  68 };
  69
  70 /* ----- follow a symbolic link ------------------------------------------ */
  71
  72 static struct dentry *ncp_follow_link(struct dentry *dentry,
  73                                       struct dentry *base,
  74                                       unsigned int follow)
  75 {
  76         struct inode *inode=dentry->d_inode;
  77         int error, length, cnt;
  78         char *link;
  79
  80 #ifdef DEBUG
  81         PRINTK("ncp_follow_link(dentry=%p,base=%p,follow=%u)\n",dentry,base,follow);
  82 #endif
  83
  84         if(!S_ISLNK(inode->i_mode)) {
  85                 dput(base);
  86                 return ERR_PTR(-EINVAL);
  87         }
  88
  89         if(ncp_make_open(inode,O_RDONLY)) {
  90                 dput(base);
  91                 return ERR_PTR(-EIO);
  92         }
  93
  94         for (cnt = 0; (link=(char *)kmalloc(NCP_MAX_SYMLINK_SIZE+1, GFP_NFS))==NULL; cnt++) {
  95                 if (cnt > 10) {
  96                         dput(base);
  97                         return ERR_PTR(-EAGAIN); /* -ENOMEM? */
  98                 }
  99                 schedule();
 100         }
 101
 102         error=ncp_read_kernel(NCP_SERVER(inode),NCP_FINFO(inode)->file_handle,
 103                          0,NCP_MAX_SYMLINK_SIZE,link,&length);
 104
 105         if (error!=0 || length<NCP_MIN_SYMLINK_SIZE ||
 106            ((__u32 *)link)[0]!=NCP_SYMLINK_MAGIC0 || ((__u32 *)link)[1]!=NCP_SYMLINK_MAGIC1) {
 107                 dput(base);
 108                 kfree(link);
 109                 return ERR_PTR(-EIO);
 110         }
 111
 112         link[length]=0;
 113
 114         vol2io(NCP_SERVER(inode), link+8, 0);
 115
 116         /* UPDATE_ATIME(inode); */
 117         base=lookup_dentry(link+8, base, follow);
 118         kfree(link);
 119
 120         return base;
 121 }
 122
 123 /* ----- read symbolic link ---------------------------------------------- */
 124
 125 static int ncp_readlink(struct dentry * dentry, char * buffer, int buflen)
 126 {
 127         struct inode *inode=dentry->d_inode;
 128         char *link;
 129         int length,error;
 130
 131 #ifdef DEBUG
 132         PRINTK("ncp_readlink(dentry=%p,buffer=%p,buflen=%d)\n",dentry,buffer,buflen);
 133 #endif
 134
 135         if(!S_ISLNK(inode->i_mode))
 136                 return -EINVAL;
 137
 138         if(ncp_make_open(inode,O_RDONLY))
 139                 return -EIO;
 140
 141         if((link=(char *)kmalloc(NCP_MAX_SYMLINK_SIZE+1,GFP_NFS))==NULL)
 142                 return -ENOMEM;
 143
 144         error = ncp_read_kernel(NCP_SERVER(inode),NCP_FINFO(inode)->file_handle,
 145                 0,NCP_MAX_SYMLINK_SIZE,link,&length);
 146
 147         if (error!=0 || length < NCP_MIN_SYMLINK_SIZE || buflen < (length-8) ||
 148            ((__u32 *)link)[0]!=NCP_SYMLINK_MAGIC0 ||((__u32 *)link)[1]!=NCP_SYMLINK_MAGIC1) {
 149                 error = -EIO;
 150                 goto out;
 151         }
 152
 153         link[length] = 0;
 154
 155         vol2io(NCP_SERVER(inode), link+8, 0);
 156
 157         error = length - 8;
 158         if(copy_to_user(buffer, link+8, error))
 159                 error = -EFAULT;
 160
 161 out:;
 162         kfree(link);
 163         return error;
 164 }
 165
 166 /* ----- create a new symbolic link -------------------------------------- */
 167
 168 int ncp_symlink(struct inode *dir, struct dentry *dentry, const char *symname) {
 169         int i,length;
 170         struct inode *inode;
 171         char *link;
 172
 173 #ifdef DEBUG
 174         PRINTK("ncp_symlink(dir=%p,dentry=%p,symname=%s)\n",dir,dentry,symname);
 175 #endif
 176
 177         if (!(NCP_SERVER(dir)->m.flags & NCP_MOUNT_SYMLINKS))
 178                 return -EPERM;  /* EPERM is returned by VFS if symlink procedure does not exist */
 179
 180         if ((length=strlen(symname))>NCP_MAX_SYMLINK_SIZE)
 181                 return -EINVAL;
 182
 183         if ((link=(char *)kmalloc(length+9,GFP_NFS))==NULL)
 184                 return -ENOMEM;
 185
 186         if (ncp_create_new(dir,dentry,0,aSHARED|aHIDDEN)) {
 187                 kfree(link);
 188                 return -EIO;
 189         }
 190
 191         inode=dentry->d_inode;
 192
 193         ((__u32 *)link)[0]=NCP_SYMLINK_MAGIC0;
 194         ((__u32 *)link)[1]=NCP_SYMLINK_MAGIC1;
 195         memcpy(link+8, symname, length+1); /* including last zero for io2vol */
 196
 197         /* map to/from server charset, do not touch upper/lower case as
 198            symlink can point out of ncp filesystem */
 199         io2vol(NCP_SERVER(inode), link+8, 0);
 200
 201         if(ncp_write_kernel(NCP_SERVER(inode), NCP_FINFO(inode)->file_handle,
 202                             0, length+8, link, &i) || i!=length+8) {
 203                 kfree(link);
 204                 return -EIO;
 205         }
 206
 207         kfree(link);
 208         return 0;
 209 }
 210 #endif
 211
 212 /* ----- EOF ----- */