1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * Copyright (C) 2017-2018 HUAWEI, Inc.
4 * https://www.huawei.com/
5 */
6 #include "internal.h"
7
debug_one_dentry(unsigned char d_type,const char * de_name,unsigned int de_namelen)8 static void debug_one_dentry(unsigned char d_type, const char *de_name,
9 unsigned int de_namelen)
10 {
11 #ifdef CONFIG_EROFS_FS_DEBUG
12 /* since the on-disk name could not have the trailing '\0' */
13 unsigned char dbg_namebuf[EROFS_NAME_LEN + 1];
14
15 memcpy(dbg_namebuf, de_name, de_namelen);
16 dbg_namebuf[de_namelen] = '\0';
17
18 erofs_dbg("found dirent %s de_len %u d_type %d", dbg_namebuf,
19 de_namelen, d_type);
20 #endif
21 }
22
erofs_fill_dentries(struct inode * dir,struct dir_context * ctx,void * dentry_blk,unsigned int * ofs,unsigned int nameoff,unsigned int maxsize)23 static int erofs_fill_dentries(struct inode *dir, struct dir_context *ctx,
24 void *dentry_blk, unsigned int *ofs,
25 unsigned int nameoff, unsigned int maxsize)
26 {
27 struct erofs_dirent *de = dentry_blk + *ofs;
28 const struct erofs_dirent *end = dentry_blk + nameoff;
29
30 while (de < end) {
31 const char *de_name;
32 unsigned int de_namelen;
33 unsigned char d_type;
34
35 d_type = fs_ftype_to_dtype(de->file_type);
36
37 nameoff = le16_to_cpu(de->nameoff);
38 de_name = (char *)dentry_blk + nameoff;
39
40 /* the last dirent in the block? */
41 if (de + 1 >= end)
42 de_namelen = strnlen(de_name, maxsize - nameoff);
43 else
44 de_namelen = le16_to_cpu(de[1].nameoff) - nameoff;
45
46 /* a corrupted entry is found */
47 if (nameoff + de_namelen > maxsize ||
48 de_namelen > EROFS_NAME_LEN) {
49 erofs_err(dir->i_sb, "bogus dirent @ nid %llu",
50 EROFS_I(dir)->nid);
51 DBG_BUGON(1);
52 return -EFSCORRUPTED;
53 }
54
55 debug_one_dentry(d_type, de_name, de_namelen);
56 if (!dir_emit(ctx, de_name, de_namelen,
57 le64_to_cpu(de->nid), d_type))
58 /* stopped by some reason */
59 return 1;
60 ++de;
61 *ofs += sizeof(struct erofs_dirent);
62 }
63 *ofs = maxsize;
64 return 0;
65 }
66
erofs_readdir(struct file * f,struct dir_context * ctx)67 static int erofs_readdir(struct file *f, struct dir_context *ctx)
68 {
69 struct inode *dir = file_inode(f);
70 struct address_space *mapping = dir->i_mapping;
71 const size_t dirsize = i_size_read(dir);
72 unsigned int i = ctx->pos / EROFS_BLKSIZ;
73 unsigned int ofs = ctx->pos % EROFS_BLKSIZ;
74 int err = 0;
75 bool initial = true;
76
77 while (ctx->pos < dirsize) {
78 struct page *dentry_page;
79 struct erofs_dirent *de;
80 unsigned int nameoff, maxsize;
81
82 dentry_page = read_mapping_page(mapping, i, NULL);
83 if (dentry_page == ERR_PTR(-ENOMEM)) {
84 err = -ENOMEM;
85 break;
86 } else if (IS_ERR(dentry_page)) {
87 erofs_err(dir->i_sb,
88 "fail to readdir of logical block %u of nid %llu",
89 i, EROFS_I(dir)->nid);
90 err = -EFSCORRUPTED;
91 break;
92 }
93
94 de = (struct erofs_dirent *)kmap(dentry_page);
95
96 nameoff = le16_to_cpu(de->nameoff);
97
98 if (nameoff < sizeof(struct erofs_dirent) ||
99 nameoff >= PAGE_SIZE) {
100 erofs_err(dir->i_sb,
101 "invalid de[0].nameoff %u @ nid %llu",
102 nameoff, EROFS_I(dir)->nid);
103 err = -EFSCORRUPTED;
104 goto skip_this;
105 }
106
107 maxsize = min_t(unsigned int,
108 dirsize - ctx->pos + ofs, PAGE_SIZE);
109
110 /* search dirents at the arbitrary position */
111 if (initial) {
112 initial = false;
113
114 ofs = roundup(ofs, sizeof(struct erofs_dirent));
115 if (ofs >= nameoff)
116 goto skip_this;
117 }
118
119 err = erofs_fill_dentries(dir, ctx, de, &ofs,
120 nameoff, maxsize);
121 skip_this:
122 kunmap(dentry_page);
123
124 put_page(dentry_page);
125
126 ctx->pos = blknr_to_addr(i) + ofs;
127
128 if (err)
129 break;
130 ++i;
131 ofs = 0;
132 }
133 return err < 0 ? err : 0;
134 }
135
136 const struct file_operations erofs_dir_fops = {
137 .llseek = generic_file_llseek,
138 .read = generic_read_dir,
139 .iterate_shared = erofs_readdir,
140 };
141