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// SPDX-License-Identifier: GPL-2.0-only
/*
* symlink.c
*
* PURPOSE
* Symlink handling routines for the OSTA-UDF(tm) filesystem.
*
* COPYRIGHT
* (C) 1998-2001 Ben Fennema
* (C) 1999 Stelias Computing Inc
*
* HISTORY
*
* 04/16/99 blf Created.
*
*/
#include "udfdecl.h"
#include <linux/uaccess.h>
#include <linux/errno.h>
#include <linux/fs.h>
#include <linux/time.h>
#include <linux/mm.h>
#include <linux/stat.h>
#include <linux/pagemap.h>
#include "udf_i.h"
static int udf_pc_to_char(struct super_block *sb, unsigned char *from,
int fromlen, unsigned char *to, int tolen)
{
struct pathComponent *pc;
int elen = 0;
int comp_len;
unsigned char *p = to;
/* Reserve one byte for terminating \0 */
tolen--;
while (elen < fromlen) {
pc = (struct pathComponent *)(from + elen);
elen += sizeof(struct pathComponent);
switch (pc->componentType) {
case 1:
/*
* Symlink points to some place which should be agreed
* upon between originator and receiver of the media. Ignore.
*/
if (pc->lengthComponentIdent > 0) {
elen += pc->lengthComponentIdent;
break;
}
fallthrough;
case 2:
if (tolen == 0)
return -ENAMETOOLONG;
p = to;
*p++ = '/';
tolen--;
break;
case 3:
if (tolen < 3)
return -ENAMETOOLONG;
memcpy(p, "../", 3);
p += 3;
tolen -= 3;
break;
case 4:
if (tolen < 2)
return -ENAMETOOLONG;
memcpy(p, "./", 2);
p += 2;
tolen -= 2;
/* that would be . - just ignore */
break;
case 5:
elen += pc->lengthComponentIdent;
if (elen > fromlen)
return -EIO;
comp_len = udf_get_filename(sb, pc->componentIdent,
pc->lengthComponentIdent,
p, tolen);
if (comp_len < 0)
return comp_len;
p += comp_len;
tolen -= comp_len;
if (tolen == 0)
return -ENAMETOOLONG;
*p++ = '/';
tolen--;
break;
}
}
if (p > to + 1)
p[-1] = '\0';
else
p[0] = '\0';
return 0;
}
static int udf_symlink_filler(struct file *file, struct folio *folio)
{
struct inode *inode = folio->mapping->host;
struct buffer_head *bh = NULL;
unsigned char *symlink;
int err = 0;
unsigned char *p = folio_address(folio);
struct udf_inode_info *iinfo = UDF_I(inode);
/* We don't support symlinks longer than one block */
if (inode->i_size > inode->i_sb->s_blocksize) {
err = -ENAMETOOLONG;
goto out;
}
if (iinfo->i_alloc_type == ICBTAG_FLAG_AD_IN_ICB) {
symlink = iinfo->i_data + iinfo->i_lenEAttr;
} else {
bh = udf_bread(inode, 0, 0, &err);
if (!bh) {
if (!err)
err = -EFSCORRUPTED;
goto out;
}
symlink = bh->b_data;
}
err = udf_pc_to_char(inode->i_sb, symlink, inode->i_size, p, PAGE_SIZE);
brelse(bh);
out:
folio_end_read(folio, err == 0);
return err;
}
static int udf_symlink_getattr(struct mnt_idmap *idmap,
const struct path *path, struct kstat *stat,
u32 request_mask, unsigned int flags)
{
struct dentry *dentry = path->dentry;
struct inode *inode = d_backing_inode(dentry);
struct folio *folio;
generic_fillattr(&nop_mnt_idmap, request_mask, inode, stat);
folio = read_mapping_folio(inode->i_mapping, 0, NULL);
if (IS_ERR(folio))
return PTR_ERR(folio);
/*
* UDF uses non-trivial encoding of symlinks so i_size does not match
* number of characters reported by readlink(2) which apparently some
* applications expect. Also POSIX says that "The value returned in the
* st_size field shall be the length of the contents of the symbolic
* link, and shall not count a trailing null if one is present." So
* let's report the length of string returned by readlink(2) for
* st_size.
*/
stat->size = strlen(folio_address(folio));
folio_put(folio);
return 0;
}
/*
* symlinks can't do much...
*/
const struct address_space_operations udf_symlink_aops = {
.read_folio = udf_symlink_filler,
};
const struct inode_operations udf_symlink_inode_operations = {
.get_link = page_get_link,
.getattr = udf_symlink_getattr,
};
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