1/*
2 *  linux/fs/ext4/symlink.c
3 *
4 * Only fast symlinks left here - the rest is done by generic code. AV, 1999
5 *
6 * Copyright (C) 1992, 1993, 1994, 1995
7 * Remy Card (card@masi.ibp.fr)
8 * Laboratoire MASI - Institut Blaise Pascal
9 * Universite Pierre et Marie Curie (Paris VI)
10 *
11 *  from
12 *
13 *  linux/fs/minix/symlink.c
14 *
15 *  Copyright (C) 1991, 1992  Linus Torvalds
16 *
17 *  ext4 symlink handling code
18 */
19
20#include <linux/fs.h>
21#include <linux/namei.h>
22#include "ext4.h"
23#include "xattr.h"
24
25#ifdef CONFIG_EXT4_FS_ENCRYPTION
26static void *ext4_follow_link(struct dentry *dentry, struct nameidata *nd)
27{
28	struct page *cpage = NULL;
29	char *caddr, *paddr = NULL;
30	struct ext4_str cstr, pstr;
31	struct inode *inode = d_inode(dentry);
32	struct ext4_fname_crypto_ctx *ctx = NULL;
33	struct ext4_encrypted_symlink_data *sd;
34	loff_t size = min_t(loff_t, i_size_read(inode), PAGE_SIZE - 1);
35	int res;
36	u32 plen, max_size = inode->i_sb->s_blocksize;
37
38	if (!ext4_encrypted_inode(inode))
39		return page_follow_link_light(dentry, nd);
40
41	ctx = ext4_get_fname_crypto_ctx(inode, inode->i_sb->s_blocksize);
42	if (IS_ERR(ctx))
43		return ctx;
44
45	if (ext4_inode_is_fast_symlink(inode)) {
46		caddr = (char *) EXT4_I(inode)->i_data;
47		max_size = sizeof(EXT4_I(inode)->i_data);
48	} else {
49		cpage = read_mapping_page(inode->i_mapping, 0, NULL);
50		if (IS_ERR(cpage)) {
51			ext4_put_fname_crypto_ctx(&ctx);
52			return cpage;
53		}
54		caddr = kmap(cpage);
55		caddr[size] = 0;
56	}
57
58	/* Symlink is encrypted */
59	sd = (struct ext4_encrypted_symlink_data *)caddr;
60	cstr.name = sd->encrypted_path;
61	cstr.len  = le32_to_cpu(sd->len);
62	if ((cstr.len +
63	     sizeof(struct ext4_encrypted_symlink_data) - 1) >
64	    max_size) {
65		/* Symlink data on the disk is corrupted */
66		res = -EIO;
67		goto errout;
68	}
69	plen = (cstr.len < EXT4_FNAME_CRYPTO_DIGEST_SIZE*2) ?
70		EXT4_FNAME_CRYPTO_DIGEST_SIZE*2 : cstr.len;
71	paddr = kmalloc(plen + 1, GFP_NOFS);
72	if (!paddr) {
73		res = -ENOMEM;
74		goto errout;
75	}
76	pstr.name = paddr;
77	res = _ext4_fname_disk_to_usr(ctx, NULL, &cstr, &pstr);
78	if (res < 0)
79		goto errout;
80	/* Null-terminate the name */
81	if (res <= plen)
82		paddr[res] = '\0';
83	nd_set_link(nd, paddr);
84	ext4_put_fname_crypto_ctx(&ctx);
85	if (cpage) {
86		kunmap(cpage);
87		page_cache_release(cpage);
88	}
89	return NULL;
90errout:
91	ext4_put_fname_crypto_ctx(&ctx);
92	if (cpage) {
93		kunmap(cpage);
94		page_cache_release(cpage);
95	}
96	kfree(paddr);
97	return ERR_PTR(res);
98}
99
100static void ext4_put_link(struct dentry *dentry, struct nameidata *nd,
101			  void *cookie)
102{
103	struct page *page = cookie;
104
105	if (!page) {
106		kfree(nd_get_link(nd));
107	} else {
108		kunmap(page);
109		page_cache_release(page);
110	}
111}
112#endif
113
114static void *ext4_follow_fast_link(struct dentry *dentry, struct nameidata *nd)
115{
116	struct ext4_inode_info *ei = EXT4_I(d_inode(dentry));
117	nd_set_link(nd, (char *) ei->i_data);
118	return NULL;
119}
120
121const struct inode_operations ext4_symlink_inode_operations = {
122	.readlink	= generic_readlink,
123#ifdef CONFIG_EXT4_FS_ENCRYPTION
124	.follow_link    = ext4_follow_link,
125	.put_link       = ext4_put_link,
126#else
127	.follow_link	= page_follow_link_light,
128	.put_link	= page_put_link,
129#endif
130	.setattr	= ext4_setattr,
131	.setxattr	= generic_setxattr,
132	.getxattr	= generic_getxattr,
133	.listxattr	= ext4_listxattr,
134	.removexattr	= generic_removexattr,
135};
136
137const struct inode_operations ext4_fast_symlink_inode_operations = {
138	.readlink	= generic_readlink,
139	.follow_link    = ext4_follow_fast_link,
140	.setattr	= ext4_setattr,
141	.setxattr	= generic_setxattr,
142	.getxattr	= generic_getxattr,
143	.listxattr	= ext4_listxattr,
144	.removexattr	= generic_removexattr,
145};
146