symlink.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright (C) 2018 Ernesto A. Fernández <ernesto.mnd.fernandez@gmail.com>
 */

#include<linux/fs.h>
#include<linux/slab.h>
#include"apfs.h"

/**
 * apfs_get_link - Follow a symbolic link
 * @dentry: dentry for the link
 * @inode: inode for the link
 * @done: delayed call to free the returned buffer after use
 *
 * Returns a pointer to a buffer containing the target path, or an appropriate
 * error pointer in case of failure.
 */
staticconstchar*apfs_get_link(structdentry*dentry, structinode*inode,
structdelayed_call*done)
{
structsuper_block*sb=inode->i_sb;
structapfs_nxsb_info*nxi=APFS_NXI(sb);
char*target=NULL;
interr;
intsize;

down_read(&nxi->nx_big_sem);

if (!dentry) {
err=-ECHILD;
 goto fail;
 }

size=__apfs_xattr_get(inode, APFS_XATTR_NAME_SYMLINK,
NULL/* buffer */, 0/* size */);
if (size<0) { /* TODO: return a better error code */
apfs_err(sb, "symlink size read failed");
err=size;
 goto fail;
 }

target=kmalloc(size, GFP_KERNEL);
if (!target) {
err=-ENOMEM;
 goto fail;
 }

size=__apfs_xattr_get(inode, APFS_XATTR_NAME_SYMLINK, target, size);
if (size<0) {
apfs_err(sb, "symlink read failed");
err=size;
 goto fail;
 }
if (size==0||*(target+size-1) !=0) {
/* Target path must be NULL-terminated */
apfs_err(sb, "bad link target in inode 0x%llx", apfs_ino(inode));
err=-EFSCORRUPTED;
 goto fail;
 }

up_read(&nxi->nx_big_sem);
set_delayed_call(done, kfree_link, target);
returntarget;

fail:
kfree(target);
up_read(&nxi->nx_big_sem);
returnERR_PTR(err);
}

conststructinode_operationsapfs_symlink_inode_operations= {
 .get_link=apfs_get_link,
 .getattr=apfs_getattr,
 .listxattr=apfs_listxattr,
 .update_time=apfs_update_time,
#ifLINUX_VERSION_CODE<KERNEL_VERSION(4, 10, 0) /* Now this is the default */
 .readlink=generic_readlink,
#endif
};