xref: /kernel/linux/linux-5.10/fs/erofs/dir.c (revision 8c2ecf20) 
1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * Copyright (C) 2017-2018 HUAWEI, Inc.
4 *             https://www.huawei.com/
5 * Created by Gao Xiang <gaoxiang25@huawei.com>
6 */
7#include "internal.h"
8
9static void debug_one_dentry(unsigned char d_type, const char *de_name,
10			     unsigned int de_namelen)
11{
12#ifdef CONFIG_EROFS_FS_DEBUG
13	/* since the on-disk name could not have the trailing '\0' */
14	unsigned char dbg_namebuf[EROFS_NAME_LEN + 1];
15
16	memcpy(dbg_namebuf, de_name, de_namelen);
17	dbg_namebuf[de_namelen] = '\0';
18
19	erofs_dbg("found dirent %s de_len %u d_type %d", dbg_namebuf,
20		  de_namelen, d_type);
21#endif
22}
23
24static int erofs_fill_dentries(struct inode *dir, struct dir_context *ctx,
25			       void *dentry_blk, unsigned int *ofs,
26			       unsigned int nameoff, unsigned int maxsize)
27{
28	struct erofs_dirent *de = dentry_blk + *ofs;
29	const struct erofs_dirent *end = dentry_blk + nameoff;
30
31	while (de < end) {
32		const char *de_name;
33		unsigned int de_namelen;
34		unsigned char d_type;
35
36		d_type = fs_ftype_to_dtype(de->file_type);
37
38		nameoff = le16_to_cpu(de->nameoff);
39		de_name = (char *)dentry_blk + nameoff;
40
41		/* the last dirent in the block? */
42		if (de + 1 >= end)
43			de_namelen = strnlen(de_name, maxsize - nameoff);
44		else
45			de_namelen = le16_to_cpu(de[1].nameoff) - nameoff;
46
47		/* a corrupted entry is found */
48		if (nameoff + de_namelen > maxsize ||
49		    de_namelen > EROFS_NAME_LEN) {
50			erofs_err(dir->i_sb, "bogus dirent @ nid %llu",
51				  EROFS_I(dir)->nid);
52			DBG_BUGON(1);
53			return -EFSCORRUPTED;
54		}
55
56		debug_one_dentry(d_type, de_name, de_namelen);
57		if (!dir_emit(ctx, de_name, de_namelen,
58			      le64_to_cpu(de->nid), d_type))
59			/* stopped by some reason */
60			return 1;
61		++de;
62		*ofs += sizeof(struct erofs_dirent);
63	}
64	*ofs = maxsize;
65	return 0;
66}
67
68static int erofs_readdir(struct file *f, struct dir_context *ctx)
69{
70	struct inode *dir = file_inode(f);
71	struct address_space *mapping = dir->i_mapping;
72	const size_t dirsize = i_size_read(dir);
73	unsigned int i = ctx->pos / EROFS_BLKSIZ;
74	unsigned int ofs = ctx->pos % EROFS_BLKSIZ;
75	int err = 0;
76	bool initial = true;
77
78	while (ctx->pos < dirsize) {
79		struct page *dentry_page;
80		struct erofs_dirent *de;
81		unsigned int nameoff, maxsize;
82
83		dentry_page = read_mapping_page(mapping, i, NULL);
84		if (dentry_page == ERR_PTR(-ENOMEM)) {
85			err = -ENOMEM;
86			break;
87		} else if (IS_ERR(dentry_page)) {
88			erofs_err(dir->i_sb,
89				  "fail to readdir of logical block %u of nid %llu",
90				  i, EROFS_I(dir)->nid);
91			err = -EFSCORRUPTED;
92			break;
93		}
94
95		de = (struct erofs_dirent *)kmap(dentry_page);
96
97		nameoff = le16_to_cpu(de->nameoff);
98
99		if (nameoff < sizeof(struct erofs_dirent) ||
100		    nameoff >= PAGE_SIZE) {
101			erofs_err(dir->i_sb,
102				  "invalid de[0].nameoff %u @ nid %llu",
103				  nameoff, EROFS_I(dir)->nid);
104			err = -EFSCORRUPTED;
105			goto skip_this;
106		}
107
108		maxsize = min_t(unsigned int,
109				dirsize - ctx->pos + ofs, PAGE_SIZE);
110
111		/* search dirents at the arbitrary position */
112		if (initial) {
113			initial = false;
114
115			ofs = roundup(ofs, sizeof(struct erofs_dirent));
116			if (ofs >= nameoff)
117				goto skip_this;
118		}
119
120		err = erofs_fill_dentries(dir, ctx, de, &ofs,
121					  nameoff, maxsize);
122skip_this:
123		kunmap(dentry_page);
124
125		put_page(dentry_page);
126
127		ctx->pos = blknr_to_addr(i) + ofs;
128
129		if (err)
130			break;
131		++i;
132		ofs = 0;
133	}
134	return err < 0 ? err : 0;
135}
136
137const struct file_operations erofs_dir_fops = {
138	.llseek		= generic_file_llseek,
139	.read		= generic_read_dir,
140	.iterate_shared	= erofs_readdir,
141};
142
143