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