| 1 | |
| 2 | |
| 3 | * symlink.c
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| 4 | *
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| 5 | * PURPOSE
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| 6 | * Symlink handling routines for the OSTA-UDF(tm) filesystem.
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| 7 | *
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| 8 | * COPYRIGHT
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| 9 | * (C) 1998-2001 Ben Fennema
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| 10 | * (C) 1999 Stelias Computing Inc
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| 11 | *
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| 12 | * HISTORY
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| 13 | *
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| 14 | * 04/16/99 blf Created.
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| 15 | *
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| 16 |
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| 17 |
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| 18 | #include "udfdecl.h"
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| 19 | #include <linux/uaccess.h>
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| 20 | #include <linux/errno.h>
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| 21 | #include <linux/fs.h>
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| 22 | #include <linux/time.h>
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| 23 | #include <linux/mm.h>
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| 24 | #include <linux/stat.h>
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| 25 | #include <linux/pagemap.h>
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| 26 | #include "udf_i.h"
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| 27 |
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| 28 | static int udf_pc_to_char(struct super_block *sb, unsigned char *from,
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| 29 | int fromlen, unsigned char *to, int tolen)
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| 30 | {
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| 31 | struct pathComponent *pc;
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| 32 | int elen = 0;
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| 33 | int comp_len;
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| 34 | unsigned char *p = to;
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| 35 |
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| 36 |
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| 37 | tolen--;
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| 38 | while (elen < fromlen) {
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| 39 | if (fromlen - elen < sizeof(struct pathComponent))
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| 40 | return -EIO;
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| 41 | pc = (struct pathComponent *)(from + elen);
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| 42 | elen += sizeof(struct pathComponent);
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| 43 | switch (pc->componentType) {
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| 44 | case 1:
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| 45 | |
| 46 | * Symlink points to some place which should be agreed
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| 47 | * upon between originator and receiver of the media. Ignore.
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| 48 |
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| 49 | if (pc->lengthComponentIdent > 0) {
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| 50 | elen += pc->lengthComponentIdent;
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| 51 | break;
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| 52 | }
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| 53 | fallthrough;
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| 54 | case 2:
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| 55 | if (tolen == 0)
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| 56 | return -ENAMETOOLONG;
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| 57 | p = to;
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| 58 | *p++ = '/';
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| 59 | tolen--;
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| 60 | break;
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| 61 | case 3:
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| 62 | if (tolen < 3)
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| 63 | return -ENAMETOOLONG;
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| 64 | memcpy(p, "../", 3);
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| 65 | p += 3;
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| 66 | tolen -= 3;
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| 67 | break;
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| 68 | case 4:
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| 69 | if (tolen < 2)
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| 70 | return -ENAMETOOLONG;
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| 71 | memcpy(p, "./", 2);
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| 72 | p += 2;
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| 73 | tolen -= 2;
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| 74 |
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| 75 | break;
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| 76 | case 5:
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| 77 | elen += pc->lengthComponentIdent;
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| 78 | if (elen > fromlen)
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| 79 | return -EIO;
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| 80 | comp_len = udf_get_filename(sb, pc->componentIdent,
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| 81 | pc->lengthComponentIdent,
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| 82 | p, tolen);
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| 83 | if (comp_len < 0)
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| 84 | return comp_len;
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| 85 |
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| 86 | p += comp_len;
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| 87 | tolen -= comp_len;
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| 88 | if (tolen == 0)
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| 89 | return -ENAMETOOLONG;
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| 90 | *p++ = '/';
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| 91 | tolen--;
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| 92 | break;
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| 93 | }
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| 94 | }
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| 95 | if (p > to + 1)
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| 96 | p[-1] = '\0';
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| 97 | else
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| 98 | p[0] = '\0';
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| 99 | return 0;
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| 100 | }
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| 101 |
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| 102 | static int udf_symlink_filler(struct file *file, struct folio *folio)
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| 103 | {
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| 104 | struct inode *inode = folio->mapping->host;
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| 105 | struct buffer_head *bh = NULL;
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| 106 | unsigned char *symlink;
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| 107 | int err = 0;
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| 108 | unsigned char *p = folio_address(folio);
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| 109 | struct udf_inode_info *iinfo = UDF_I(inode);
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| 110 |
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| 111 |
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| 112 | if (inode->i_size > inode->i_sb->s_blocksize) {
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| 113 | err = -ENAMETOOLONG;
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| 114 | goto out;
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| 115 | }
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| 116 |
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| 117 | if (iinfo->i_alloc_type == ICBTAG_FLAG_AD_IN_ICB) {
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| 118 | symlink = iinfo->i_data + iinfo->i_lenEAttr;
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| 119 | } else {
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| 120 | bh = udf_bread(inode, 0, 0, &err);
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| 121 | if (!bh) {
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| 122 | if (!err)
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| 123 | err = -EFSCORRUPTED;
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| 124 | goto out;
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| 125 | }
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| 126 | symlink = bh->b_data;
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| 127 | }
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| 128 |
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| 129 | err = udf_pc_to_char(inode->i_sb, symlink, inode->i_size, p, PAGE_SIZE);
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| 130 | brelse(bh);
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| 131 | out:
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| 132 | folio_end_read(folio, err == 0);
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| 133 | return err;
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| 134 | }
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| 135 |
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| 136 | static int udf_symlink_getattr(const struct mnt_idmap *idmap,
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| 137 | const struct path *path, struct kstat *stat,
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| 138 | u32 request_mask, unsigned int flags)
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| 139 | {
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| 140 | struct dentry *dentry = path->dentry;
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| 141 | struct inode *inode = d_backing_inode(dentry);
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| 142 | struct folio *folio;
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| 143 |
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| 144 | generic_fillattr(&nop_mnt_idmap, request_mask, inode, stat);
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| 145 | folio = read_mapping_folio(inode->i_mapping, 0, NULL);
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| 146 | if (IS_ERR(folio))
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| 147 | return PTR_ERR(folio);
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| 148 | |
| 149 | * UDF uses non-trivial encoding of symlinks so i_size does not match
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| 150 | * number of characters reported by readlink(2) which apparently some
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| 151 | * applications expect. Also POSIX says that "The value returned in the
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| 152 | * st_size field shall be the length of the contents of the symbolic
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| 153 | * link, and shall not count a trailing null if one is present." So
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| 154 | * let's report the length of string returned by readlink(2) for
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| 155 | * st_size.
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| 156 |
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| 157 | stat->size = strlen(folio_address(folio));
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| 158 | folio_put(folio);
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| 159 |
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| 160 | return 0;
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| 161 | }
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| 162 |
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| 163 | |
| 164 | * symlinks can't do much...
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| 165 |
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| 166 | const struct address_space_operations udf_symlink_aops = {
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| 167 | .read_folio = udf_symlink_filler,
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| 168 | };
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| 169 |
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| 170 | const struct inode_operations udf_symlink_inode_operations = {
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| 171 | .get_link = page_get_link,
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| 172 | .getattr = udf_symlink_getattr,
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| 173 | };
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