1 /*
2 * symlink.c --- make a symlink in the filesystem, based on mkdir.c
3 *
4 * Copyright (c) 2012, Intel Corporation.
5 * All Rights Reserved.
6 *
7 * %Begin-Header%
8 * This file may be redistributed under the terms of the GNU Library
9 * General Public License, version 2.
10 * %End-Header%
11 */
12
13 #include "config.h"
14 #include <stdio.h>
15 #include <string.h>
16 #if HAVE_UNISTD_H
17 #include <unistd.h>
18 #endif
19 #include <fcntl.h>
20 #include <time.h>
21 #if HAVE_SYS_STAT_H
22 #include <sys/stat.h>
23 #endif
24 #if HAVE_SYS_TYPES_H
25 #include <sys/types.h>
26 #endif
27
28 #include "ext2_fs.h"
29 #include "ext2fs.h"
30
31 #ifndef HAVE_STRNLEN
32 /*
33 * Incredibly, libc5 doesn't appear to have strnlen. So we have to
34 * provide our own.
35 */
my_strnlen(const char * s,int count)36 static int my_strnlen(const char * s, int count)
37 {
38 const char *cp = s;
39
40 while (count-- && *cp)
41 cp++;
42 return cp - s;
43 }
44 #define strnlen(str, x) my_strnlen((str),(x))
45 #endif
46
ext2fs_symlink(ext2_filsys fs,ext2_ino_t parent,ext2_ino_t ino,const char * name,const char * target)47 errcode_t ext2fs_symlink(ext2_filsys fs, ext2_ino_t parent, ext2_ino_t ino,
48 const char *name, const char *target)
49 {
50 errcode_t retval;
51 struct ext2_inode inode;
52 ext2_ino_t scratch_ino;
53 blk64_t blk;
54 int fastlink, inlinelink;
55 unsigned int target_len;
56 char *block_buf = 0;
57
58 EXT2_CHECK_MAGIC(fs, EXT2_ET_MAGIC_EXT2FS_FILSYS);
59
60 /*
61 * The Linux kernel doesn't allow for links longer than a block
62 * (counting the NUL terminator)
63 */
64 target_len = strnlen(target, fs->blocksize + 1);
65 if (target_len >= fs->blocksize) {
66 retval = EXT2_ET_INVALID_ARGUMENT;
67 goto cleanup;
68 }
69
70 /*
71 * Allocate a data block for slow links
72 */
73 retval = ext2fs_get_mem(fs->blocksize, &block_buf);
74 if (retval)
75 goto cleanup;
76 memset(block_buf, 0, fs->blocksize);
77 strncpy(block_buf, target, fs->blocksize);
78
79 memset(&inode, 0, sizeof(struct ext2_inode));
80 fastlink = (target_len < sizeof(inode.i_block));
81 if (!fastlink) {
82 retval = ext2fs_new_block2(fs, ext2fs_find_inode_goal(fs, ino,
83 &inode,
84 0),
85 NULL, &blk);
86 if (retval)
87 goto cleanup;
88 }
89
90 /*
91 * Allocate an inode, if necessary
92 */
93 if (!ino) {
94 retval = ext2fs_new_inode(fs, parent, LINUX_S_IFLNK | 0755,
95 0, &ino);
96 if (retval)
97 goto cleanup;
98 }
99
100 /*
101 * Create the inode structure....
102 */
103 inode.i_mode = LINUX_S_IFLNK | 0777;
104 inode.i_uid = inode.i_gid = 0;
105 inode.i_links_count = 1;
106 ext2fs_inode_size_set(fs, &inode, target_len);
107 /* The time fields are set by ext2fs_write_new_inode() */
108
109 inlinelink = !fastlink && ext2fs_has_feature_inline_data(fs->super);
110 if (fastlink) {
111 /* Fast symlinks, target stored in inode */
112 strcpy((char *)&inode.i_block, target);
113 } else if (inlinelink) {
114 /* Try inserting an inline data symlink */
115 inode.i_flags |= EXT4_INLINE_DATA_FL;
116 retval = ext2fs_write_new_inode(fs, ino, &inode);
117 if (retval)
118 goto cleanup;
119 retval = ext2fs_inline_data_set(fs, ino, &inode, block_buf,
120 target_len);
121 if (retval) {
122 inode.i_flags &= ~EXT4_INLINE_DATA_FL;
123 inlinelink = 0;
124 goto need_block;
125 }
126 retval = ext2fs_read_inode(fs, ino, &inode);
127 if (retval)
128 goto cleanup;
129 } else {
130 need_block:
131 /* Slow symlinks, target stored in the first block */
132 ext2fs_iblk_set(fs, &inode, 1);
133 if (ext2fs_has_feature_extents(fs->super)) {
134 /*
135 * The extent bmap is setup after the inode and block
136 * have been written out below.
137 */
138 inode.i_flags |= EXT4_EXTENTS_FL;
139 }
140 }
141
142 /*
143 * Write out the inode and inode data block. The inode generation
144 * number is assigned by write_new_inode, which means that the
145 * operations using ino must come after it.
146 */
147 if (inlinelink)
148 retval = ext2fs_write_inode(fs, ino, &inode);
149 else
150 retval = ext2fs_write_new_inode(fs, ino, &inode);
151 if (retval)
152 goto cleanup;
153
154 if (!fastlink && !inlinelink) {
155 retval = ext2fs_bmap2(fs, ino, &inode, NULL, BMAP_SET, 0, NULL,
156 &blk);
157 if (retval)
158 goto cleanup;
159
160 retval = io_channel_write_blk64(fs->io, blk, 1, block_buf);
161 if (retval)
162 goto cleanup;
163 }
164
165 /*
166 * Link the symlink into the filesystem hierarchy
167 */
168 if (name) {
169 retval = ext2fs_lookup(fs, parent, name, strlen(name), 0,
170 &scratch_ino);
171 if (!retval) {
172 retval = EXT2_ET_FILE_EXISTS;
173 goto cleanup;
174 }
175 if (retval != EXT2_ET_FILE_NOT_FOUND)
176 goto cleanup;
177 retval = ext2fs_link(fs, parent, name, ino, EXT2_FT_SYMLINK);
178 if (retval)
179 goto cleanup;
180 }
181
182 /*
183 * Update accounting....
184 */
185 if (!fastlink && !inlinelink)
186 ext2fs_block_alloc_stats2(fs, blk, +1);
187 ext2fs_inode_alloc_stats2(fs, ino, +1, 0);
188
189 cleanup:
190 if (block_buf)
191 ext2fs_free_mem(&block_buf);
192 return retval;
193 }
194
195 /*
196 * Test whether an inode is a fast symlink.
197 *
198 * A fast symlink has its symlink data stored in inode->i_block.
199 */
ext2fs_is_fast_symlink(struct ext2_inode * inode)200 int ext2fs_is_fast_symlink(struct ext2_inode *inode)
201 {
202 return LINUX_S_ISLNK(inode->i_mode) && EXT2_I_SIZE(inode) &&
203 EXT2_I_SIZE(inode) < sizeof(inode->i_block);
204 }
205