| 1 | // SPDX-License-Identifier: GPL-2.0-only |
| 2 | /* |
| 3 | * symlink.c |
| 4 | * |
| 5 | * PURPOSE |
| 6 | * Symlink handling routines for the OSTA-UDF(tm) filesystem. |
| 7 | * |
| 8 | * COPYRIGHT |
| 9 | * (C) 1998-2001 Ben Fennema |
| 10 | * (C) 1999 Stelias Computing Inc |
| 11 | * |
| 12 | * HISTORY |
| 13 | * |
| 14 | * 04/16/99 blf Created. |
| 15 | * |
| 16 | */ |
| 17 | |
| 18 | #include "udfdecl.h" |
| 19 | #include <linux/uaccess.h> |
| 20 | #include <linux/errno.h> |
| 21 | #include <linux/fs.h> |
| 22 | #include <linux/time.h> |
| 23 | #include <linux/mm.h> |
| 24 | #include <linux/stat.h> |
| 25 | #include <linux/pagemap.h> |
| 26 | #include "udf_i.h" |
| 27 | |
| 28 | static int udf_pc_to_char(struct super_block *sb, unsigned char *from, |
| 29 | int fromlen, unsigned char *to, int tolen) |
| 30 | { |
| 31 | struct pathComponent *pc; |
| 32 | int elen = 0; |
| 33 | int comp_len; |
| 34 | unsigned char *p = to; |
| 35 | |
| 36 | /* Reserve one byte for terminating \0 */ |
| 37 | tolen--; |
| 38 | while (elen < fromlen) { |
| 39 | pc = (struct pathComponent *)(from + elen); |
| 40 | elen += sizeof(struct pathComponent); |
| 41 | switch (pc->componentType) { |
| 42 | case 1: |
| 43 | /* |
| 44 | * Symlink points to some place which should be agreed |
| 45 | * upon between originator and receiver of the media. Ignore. |
| 46 | */ |
| 47 | if (pc->lengthComponentIdent > 0) { |
| 48 | elen += pc->lengthComponentIdent; |
| 49 | break; |
| 50 | } |
| 51 | fallthrough; |
| 52 | case 2: |
| 53 | if (tolen == 0) |
| 54 | return -ENAMETOOLONG; |
| 55 | p = to; |
| 56 | *p++ = '/'; |
| 57 | tolen--; |
| 58 | break; |
| 59 | case 3: |
| 60 | if (tolen < 3) |
| 61 | return -ENAMETOOLONG; |
| 62 | memcpy(p, "../", 3); |
| 63 | p += 3; |
| 64 | tolen -= 3; |
| 65 | break; |
| 66 | case 4: |
| 67 | if (tolen < 2) |
| 68 | return -ENAMETOOLONG; |
| 69 | memcpy(p, "./", 2); |
| 70 | p += 2; |
| 71 | tolen -= 2; |
| 72 | /* that would be . - just ignore */ |
| 73 | break; |
| 74 | case 5: |
| 75 | elen += pc->lengthComponentIdent; |
| 76 | if (elen > fromlen) |
| 77 | return -EIO; |
| 78 | comp_len = udf_get_filename(sb, pc->componentIdent, |
| 79 | pc->lengthComponentIdent, |
| 80 | p, tolen); |
| 81 | if (comp_len < 0) |
| 82 | return comp_len; |
| 83 | |
| 84 | p += comp_len; |
| 85 | tolen -= comp_len; |
| 86 | if (tolen == 0) |
| 87 | return -ENAMETOOLONG; |
| 88 | *p++ = '/'; |
| 89 | tolen--; |
| 90 | break; |
| 91 | } |
| 92 | } |
| 93 | if (p > to + 1) |
| 94 | p[-1] = '\0'; |
| 95 | else |
| 96 | p[0] = '\0'; |
| 97 | return 0; |
| 98 | } |
| 99 | |
| 100 | static int udf_symlink_filler(struct file *file, struct folio *folio) |
| 101 | { |
| 102 | struct inode *inode = folio->mapping->host; |
| 103 | struct buffer_head *bh = NULL; |
| 104 | unsigned char *symlink; |
| 105 | int err = 0; |
| 106 | unsigned char *p = folio_address(folio); |
| 107 | struct udf_inode_info *iinfo = UDF_I(inode); |
| 108 | |
| 109 | /* We don't support symlinks longer than one block */ |
| 110 | if (inode->i_size > inode->i_sb->s_blocksize) { |
| 111 | err = -ENAMETOOLONG; |
| 112 | goto out; |
| 113 | } |
| 114 | |
| 115 | if (iinfo->i_alloc_type == ICBTAG_FLAG_AD_IN_ICB) { |
| 116 | symlink = iinfo->i_data + iinfo->i_lenEAttr; |
| 117 | } else { |
| 118 | bh = udf_bread(inode, 0, 0, &err); |
| 119 | if (!bh) { |
| 120 | if (!err) |
| 121 | err = -EFSCORRUPTED; |
| 122 | goto out; |
| 123 | } |
| 124 | symlink = bh->b_data; |
| 125 | } |
| 126 | |
| 127 | err = udf_pc_to_char(inode->i_sb, symlink, inode->i_size, p, PAGE_SIZE); |
| 128 | brelse(bh); |
| 129 | out: |
| 130 | folio_end_read(folio, err == 0); |
| 131 | return err; |
| 132 | } |
| 133 | |
| 134 | static int udf_symlink_getattr(struct mnt_idmap *idmap, |
| 135 | const struct path *path, struct kstat *stat, |
| 136 | u32 request_mask, unsigned int flags) |
| 137 | { |
| 138 | struct dentry *dentry = path->dentry; |
| 139 | struct inode *inode = d_backing_inode(dentry); |
| 140 | struct folio *folio; |
| 141 | |
| 142 | generic_fillattr(&nop_mnt_idmap, request_mask, inode, stat); |
| 143 | folio = read_mapping_folio(inode->i_mapping, 0, NULL); |
| 144 | if (IS_ERR(folio)) |
| 145 | return PTR_ERR(folio); |
| 146 | /* |
| 147 | * UDF uses non-trivial encoding of symlinks so i_size does not match |
| 148 | * number of characters reported by readlink(2) which apparently some |
| 149 | * applications expect. Also POSIX says that "The value returned in the |
| 150 | * st_size field shall be the length of the contents of the symbolic |
| 151 | * link, and shall not count a trailing null if one is present." So |
| 152 | * let's report the length of string returned by readlink(2) for |
| 153 | * st_size. |
| 154 | */ |
| 155 | stat->size = strlen(folio_address(folio)); |
| 156 | folio_put(folio); |
| 157 | |
| 158 | return 0; |
| 159 | } |
| 160 | |
| 161 | /* |
| 162 | * symlinks can't do much... |
| 163 | */ |
| 164 | const struct address_space_operations udf_symlink_aops = { |
| 165 | .read_folio = udf_symlink_filler, |
| 166 | }; |
| 167 | |
| 168 | const struct inode_operations udf_symlink_inode_operations = { |
| 169 | .get_link = page_get_link, |
| 170 | .getattr = udf_symlink_getattr, |
| 171 | }; |