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 int drop_refcount = 0;
58
59 EXT2_CHECK_MAGIC(fs, EXT2_ET_MAGIC_EXT2FS_FILSYS);
60
61 /*
62 * The Linux kernel doesn't allow for links longer than a block
63 * (counting the NUL terminator)
64 */
65 target_len = strnlen(target, fs->blocksize + 1);
66 if (target_len >= fs->blocksize) {
67 retval = EXT2_ET_INVALID_ARGUMENT;
68 goto cleanup;
69 }
70
71 /*
72 * Allocate a data block for slow links
73 */
74 retval = ext2fs_get_mem(fs->blocksize, &block_buf);
75 if (retval)
76 goto cleanup;
77 memset(block_buf, 0, fs->blocksize);
78 strncpy(block_buf, target, fs->blocksize);
79
80 memset(&inode, 0, sizeof(struct ext2_inode));
81 fastlink = (target_len < sizeof(inode.i_block));
82 if (!fastlink) {
83 retval = ext2fs_new_block2(fs, ext2fs_find_inode_goal(fs, ino,
84 &inode,
85 0),
86 NULL, &blk);
87 if (retval)
88 goto cleanup;
89 }
90
91 /*
92 * Allocate an inode, if necessary
93 */
94 if (!ino) {
95 retval = ext2fs_new_inode(fs, parent, LINUX_S_IFLNK | 0755,
96 0, &ino);
97 if (retval)
98 goto cleanup;
99 }
100
101 /*
102 * Create the inode structure....
103 */
104 inode.i_mode = LINUX_S_IFLNK | 0777;
105 inode.i_uid = inode.i_gid = 0;
106 inode.i_links_count = 1;
107 ext2fs_inode_size_set(fs, &inode, target_len);
108 /* The time fields are set by ext2fs_write_new_inode() */
109
110 inlinelink = !fastlink && ext2fs_has_feature_inline_data(fs->super);
111 if (fastlink) {
112 /* Fast symlinks, target stored in inode */
113 strcpy((char *)&inode.i_block, target);
114 } else if (inlinelink) {
115 /* Try inserting an inline data symlink */
116 inode.i_flags |= EXT4_INLINE_DATA_FL;
117 retval = ext2fs_write_new_inode(fs, ino, &inode);
118 if (retval)
119 goto cleanup;
120 retval = ext2fs_inline_data_set(fs, ino, &inode, block_buf,
121 target_len);
122 if (retval) {
123 inode.i_flags &= ~EXT4_INLINE_DATA_FL;
124 inlinelink = 0;
125 goto need_block;
126 }
127 retval = ext2fs_read_inode(fs, ino, &inode);
128 if (retval)
129 goto cleanup;
130 } else {
131 need_block:
132 /* Slow symlinks, target stored in the first block */
133 ext2fs_iblk_set(fs, &inode, 1);
134 if (ext2fs_has_feature_extents(fs->super)) {
135 /*
136 * The extent bmap is setup after the inode and block
137 * have been written out below.
138 */
139 inode.i_flags |= EXT4_EXTENTS_FL;
140 }
141 }
142
143 /*
144 * Write out the inode and inode data block. The inode generation
145 * number is assigned by write_new_inode, which means that the
146 * operations using ino must come after it.
147 */
148 if (inlinelink)
149 retval = ext2fs_write_inode(fs, ino, &inode);
150 else
151 retval = ext2fs_write_new_inode(fs, ino, &inode);
152 if (retval)
153 goto cleanup;
154
155 if (!fastlink && !inlinelink) {
156 retval = ext2fs_bmap2(fs, ino, &inode, NULL, BMAP_SET, 0, NULL,
157 &blk);
158 if (retval)
159 goto cleanup;
160
161 retval = io_channel_write_blk64(fs->io, blk, 1, block_buf);
162 if (retval)
163 goto cleanup;
164 }
165
166 /*
167 * Update accounting....
168 */
169 if (!fastlink && !inlinelink)
170 ext2fs_block_alloc_stats2(fs, blk, +1);
171 ext2fs_inode_alloc_stats2(fs, ino, +1, 0);
172 drop_refcount = 1;
173
174 /*
175 * Link the symlink into the filesystem hierarchy
176 */
177 if (name) {
178 retval = ext2fs_lookup(fs, parent, name, strlen(name), 0,
179 &scratch_ino);
180 if (!retval) {
181 retval = EXT2_ET_FILE_EXISTS;
182 goto cleanup;
183 }
184 if (retval != EXT2_ET_FILE_NOT_FOUND)
185 goto cleanup;
186 retval = ext2fs_link(fs, parent, name, ino, EXT2_FT_SYMLINK);
187 if (retval)
188 goto cleanup;
189 }
190 drop_refcount = 0;
191
192 cleanup:
193 if (block_buf)
194 ext2fs_free_mem(&block_buf);
195 if (drop_refcount) {
196 if (!fastlink && !inlinelink)
197 ext2fs_block_alloc_stats2(fs, blk, -1);
198 ext2fs_inode_alloc_stats2(fs, ino, -1, 0);
199 }
200 return retval;
201 }
202
203 /*
204 * Test whether an inode is a fast symlink.
205 *
206 * A fast symlink has its symlink data stored in inode->i_block.
207 */
ext2fs_is_fast_symlink(struct ext2_inode * inode)208 int ext2fs_is_fast_symlink(struct ext2_inode *inode)
209 {
210 return LINUX_S_ISLNK(inode->i_mode) && EXT2_I_SIZE(inode) &&
211 EXT2_I_SIZE(inode) < sizeof(inode->i_block);
212 }
213