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1 : // SPDX-License-Identifier: GPL-2.0 2 : /* 3 : * fs/isofs/export.c 4 : * 5 : * (C) 2004 Paul Serice - The new inode scheme requires switching 6 : * from iget() to iget5_locked() which means 7 : * the NFS export operations have to be hand 8 : * coded because the default routines rely on 9 : * iget(). 10 : * 11 : * The following files are helpful: 12 : * 13 : * Documentation/filesystems/nfs/exporting.rst 14 : * fs/exportfs/expfs.c. 15 : */ 16 : 17 : #include "isofs.h" 18 : 19 : static struct dentry * 20 0 : isofs_export_iget(struct super_block *sb, 21 : unsigned long block, 22 : unsigned long offset, 23 : __u32 generation) 24 : { 25 0 : struct inode *inode; 26 : 27 0 : if (block == 0) 28 0 : return ERR_PTR(-ESTALE); 29 0 : inode = isofs_iget(sb, block, offset); 30 0 : if (IS_ERR(inode)) 31 0 : return ERR_CAST(inode); 32 0 : if (generation && inode->i_generation != generation) { 33 0 : iput(inode); 34 0 : return ERR_PTR(-ESTALE); 35 : } 36 0 : return d_obtain_alias(inode); 37 : } 38 : 39 : /* This function is surprisingly simple. The trick is understanding 40 : * that "child" is always a directory. So, to find its parent, you 41 : * simply need to find its ".." entry, normalize its block and offset, 42 : * and return the underlying inode. See the comments for 43 : * isofs_normalize_block_and_offset(). */ 44 0 : static struct dentry *isofs_export_get_parent(struct dentry *child) 45 : { 46 0 : unsigned long parent_block = 0; 47 0 : unsigned long parent_offset = 0; 48 0 : struct inode *child_inode = d_inode(child); 49 0 : struct iso_inode_info *e_child_inode = ISOFS_I(child_inode); 50 0 : struct iso_directory_record *de = NULL; 51 0 : struct buffer_head * bh = NULL; 52 0 : struct dentry *rv = NULL; 53 : 54 : /* "child" must always be a directory. */ 55 0 : if (!S_ISDIR(child_inode->i_mode)) { 56 0 : printk(KERN_ERR "isofs: isofs_export_get_parent(): " 57 : "child is not a directory!\n"); 58 0 : rv = ERR_PTR(-EACCES); 59 0 : goto out; 60 : } 61 : 62 : /* It is an invariant that the directory offset is zero. If 63 : * it is not zero, it means the directory failed to be 64 : * normalized for some reason. */ 65 0 : if (e_child_inode->i_iget5_offset != 0) { 66 0 : printk(KERN_ERR "isofs: isofs_export_get_parent(): " 67 : "child directory not normalized!\n"); 68 0 : rv = ERR_PTR(-EACCES); 69 0 : goto out; 70 : } 71 : 72 : /* The child inode has been normalized such that its 73 : * i_iget5_block value points to the "." entry. Fortunately, 74 : * the ".." entry is located in the same block. */ 75 0 : parent_block = e_child_inode->i_iget5_block; 76 : 77 : /* Get the block in question. */ 78 0 : bh = sb_bread(child_inode->i_sb, parent_block); 79 0 : if (bh == NULL) { 80 0 : rv = ERR_PTR(-EACCES); 81 0 : goto out; 82 : } 83 : 84 : /* This is the "." entry. */ 85 0 : de = (struct iso_directory_record*)bh->b_data; 86 : 87 : /* The ".." entry is always the second entry. */ 88 0 : parent_offset = (unsigned long)isonum_711(de->length); 89 0 : de = (struct iso_directory_record*)(bh->b_data + parent_offset); 90 : 91 : /* Verify it is in fact the ".." entry. */ 92 0 : if ((isonum_711(de->name_len) != 1) || (de->name[0] != 1)) { 93 0 : printk(KERN_ERR "isofs: Unable to find the \"..\" " 94 : "directory for NFS.\n"); 95 0 : rv = ERR_PTR(-EACCES); 96 0 : goto out; 97 : } 98 : 99 : /* Normalize */ 100 0 : isofs_normalize_block_and_offset(de, &parent_block, &parent_offset); 101 : 102 0 : rv = d_obtain_alias(isofs_iget(child_inode->i_sb, parent_block, 103 : parent_offset)); 104 0 : out: 105 0 : if (bh) 106 0 : brelse(bh); 107 0 : return rv; 108 : } 109 : 110 : static int 111 0 : isofs_export_encode_fh(struct inode *inode, 112 : __u32 *fh32, 113 : int *max_len, 114 : struct inode *parent) 115 : { 116 0 : struct iso_inode_info * ei = ISOFS_I(inode); 117 0 : int len = *max_len; 118 0 : int type = 1; 119 0 : __u16 *fh16 = (__u16*)fh32; 120 : 121 : /* 122 : * WARNING: max_len is 5 for NFSv2. Because of this 123 : * limitation, we use the lower 16 bits of fh32[1] to hold the 124 : * offset of the inode and the upper 16 bits of fh32[1] to 125 : * hold the offset of the parent. 126 : */ 127 0 : if (parent && (len < 5)) { 128 0 : *max_len = 5; 129 0 : return FILEID_INVALID; 130 0 : } else if (len < 3) { 131 0 : *max_len = 3; 132 0 : return FILEID_INVALID; 133 : } 134 : 135 0 : len = 3; 136 0 : fh32[0] = ei->i_iget5_block; 137 0 : fh16[2] = (__u16)ei->i_iget5_offset; /* fh16 [sic] */ 138 0 : fh16[3] = 0; /* avoid leaking uninitialized data */ 139 0 : fh32[2] = inode->i_generation; 140 0 : if (parent) { 141 0 : struct iso_inode_info *eparent; 142 0 : eparent = ISOFS_I(parent); 143 0 : fh32[3] = eparent->i_iget5_block; 144 0 : fh16[3] = (__u16)eparent->i_iget5_offset; /* fh16 [sic] */ 145 0 : fh32[4] = parent->i_generation; 146 0 : len = 5; 147 0 : type = 2; 148 : } 149 0 : *max_len = len; 150 0 : return type; 151 : } 152 : 153 : struct isofs_fid { 154 : u32 block; 155 : u16 offset; 156 : u16 parent_offset; 157 : u32 generation; 158 : u32 parent_block; 159 : u32 parent_generation; 160 : }; 161 : 162 0 : static struct dentry *isofs_fh_to_dentry(struct super_block *sb, 163 : struct fid *fid, int fh_len, int fh_type) 164 : { 165 0 : struct isofs_fid *ifid = (struct isofs_fid *)fid; 166 : 167 0 : if (fh_len < 3 || fh_type > 2) 168 : return NULL; 169 : 170 0 : return isofs_export_iget(sb, ifid->block, ifid->offset, 171 : ifid->generation); 172 : } 173 : 174 0 : static struct dentry *isofs_fh_to_parent(struct super_block *sb, 175 : struct fid *fid, int fh_len, int fh_type) 176 : { 177 0 : struct isofs_fid *ifid = (struct isofs_fid *)fid; 178 : 179 0 : if (fh_len < 2 || fh_type != 2) 180 : return NULL; 181 : 182 0 : return isofs_export_iget(sb, 183 0 : fh_len > 2 ? ifid->parent_block : 0, 184 0 : ifid->parent_offset, 185 : fh_len > 4 ? ifid->parent_generation : 0); 186 : } 187 : 188 : const struct export_operations isofs_export_ops = { 189 : .encode_fh = isofs_export_encode_fh, 190 : .fh_to_dentry = isofs_fh_to_dentry, 191 : .fh_to_parent = isofs_fh_to_parent, 192 : .get_parent = isofs_export_get_parent, 193 : };
