fs/fhandle.c - third_party/linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0
 #include <linux/syscalls.h>
 #include <linux/slab.h>
 #include <linux/fs.h>
 #include <linux/file.h>
 #include <linux/mount.h>
 #include <linux/namei.h>
 #include <linux/exportfs.h>
 #include <linux/fs_struct.h>
 #include <linux/fsnotify.h>
 #include <linux/personality.h>
 #include <linux/uaccess.h>
 #include <linux/compat.h>
 #include "internal.h"
 #include "mount.h"

 static long do_sys_name_to_handle(struct path *path,
 				  struct file_handle __user *ufh,
 				  int __user *mnt_id)
 {
 	long retval;
 	struct file_handle f_handle;
 	int handle_dwords, handle_bytes;
 	struct file_handle *handle = NULL;

 	/*
 	 * We need to make sure whether the file system
 	 * support decoding of the file handle
 	 */
 	if (!path->dentry->d_sb->s_export_op ||
 	    !path->dentry->d_sb->s_export_op->fh_to_dentry)
 		return -EOPNOTSUPP;

 	if (copy_from_user(&f_handle, ufh, sizeof(struct file_handle)))
 		return -EFAULT;

 	if (f_handle.handle_bytes > MAX_HANDLE_SZ)
 		return -EINVAL;

 	handle = kzalloc(sizeof(struct file_handle) + f_handle.handle_bytes,
 			 GFP_KERNEL);
 	if (!handle)
 		return -ENOMEM;

 	/* convert handle size to multiple of sizeof(u32) */
 	handle_dwords = f_handle.handle_bytes >> 2;

 	/* we ask for a non connected handle */
 	retval = exportfs_encode_fh(path->dentry,
 				    (struct fid *)handle->f_handle,
 				    &handle_dwords,  0);
 	handle->handle_type = retval;
 	/* convert handle size to bytes */
 	handle_bytes = handle_dwords * sizeof(u32);
 	handle->handle_bytes = handle_bytes;
 	if ((handle->handle_bytes > f_handle.handle_bytes) ||
 	    (retval == FILEID_INVALID) || (retval == -ENOSPC)) {
 		/* As per old exportfs_encode_fh documentation
 		 * we could return ENOSPC to indicate overflow
 		 * But file system returned 255 always. So handle
 		 * both the values
 		 */
 		/*
 		 * set the handle size to zero so we copy only
 		 * non variable part of the file_handle
 		 */
 		handle_bytes = 0;
 		retval = -EOVERFLOW;
 	} else
 		retval = 0;
 	/* copy the mount id */
 	if (put_user(real_mount(path->mnt)->mnt_id, mnt_id) ||
 	    copy_to_user(ufh, handle,
 			 sizeof(struct file_handle) + handle_bytes))
 		retval = -EFAULT;
 	kfree(handle);
 	return retval;
 }

 /**
  * sys_name_to_handle_at: convert name to handle
  * @dfd: directory relative to which name is interpreted if not absolute
  * @name: name that should be converted to handle.
  * @handle: resulting file handle
  * @mnt_id: mount id of the file system containing the file
  * @flag: flag value to indicate whether to follow symlink or not
  *
  * @handle->handle_size indicate the space available to store the
  * variable part of the file handle in bytes. If there is not
  * enough space, the field is updated to return the minimum
  * value required.
  */
 SYSCALL_DEFINE5(name_to_handle_at, int, dfd, const char __user *, name,
 		struct file_handle __user *, handle, int __user *, mnt_id,
 		int, flag)
 {
 	struct path path;
 	int lookup_flags;
 	int err;

 	if ((flag & ~(AT_SYMLINK_FOLLOW | AT_EMPTY_PATH)) != 0)
 		return -EINVAL;

 	lookup_flags = (flag & AT_SYMLINK_FOLLOW) ? LOOKUP_FOLLOW : 0;
 	if (flag & AT_EMPTY_PATH)
 		lookup_flags |= LOOKUP_EMPTY;
 	err = user_path_at(dfd, name, lookup_flags, &path);
 	if (!err) {
 		err = do_sys_name_to_handle(&path, handle, mnt_id);
 		path_put(&path);
 	}
 	return err;
 }

 static struct vfsmount *get_vfsmount_from_fd(int fd)
 {
 	struct vfsmount *mnt;

 	if (fd == AT_FDCWD) {
 		struct fs_struct *fs = current->fs;
 		spin_lock(&fs->lock);
 		mnt = mntget(fs->pwd.mnt);
 		spin_unlock(&fs->lock);
 	} else {
 		struct fd f = fdget(fd);
 		if (!f.file)
 			return ERR_PTR(-EBADF);
 		mnt = mntget(f.file->f_path.mnt);
 		fdput(f);
 	}
 	return mnt;
 }

 static int vfs_dentry_acceptable(void *context, struct dentry *dentry)
 {
 	return 1;
 }

 static int do_handle_to_path(int mountdirfd, struct file_handle *handle,
 			     struct path *path)
 {
 	int retval = 0;
 	int handle_dwords;

 	path->mnt = get_vfsmount_from_fd(mountdirfd);
 	if (IS_ERR(path->mnt)) {
 		retval = PTR_ERR(path->mnt);
 		goto out_err;
 	}
 	/* change the handle size to multiple of sizeof(u32) */
 	handle_dwords = handle->handle_bytes >> 2;
 	path->dentry = exportfs_decode_fh(path->mnt,
 					  (struct fid *)handle->f_handle,
 					  handle_dwords, handle->handle_type,
 					  vfs_dentry_acceptable, NULL);
 	if (IS_ERR(path->dentry)) {
 		retval = PTR_ERR(path->dentry);
 		goto out_mnt;
 	}
 	return 0;
 out_mnt:
 	mntput(path->mnt);
 out_err:
 	return retval;
 }

 static int handle_to_path(int mountdirfd, struct file_handle __user *ufh,
 		   struct path *path)
 {
 	int retval = 0;
 	struct file_handle f_handle;
 	struct file_handle *handle = NULL;

 	/*
 	 * With handle we don't look at the execute bit on the
 	 * the directory. Ideally we would like CAP_DAC_SEARCH.
 	 * But we don't have that
 	 */
 	if (!capable(CAP_DAC_READ_SEARCH)) {
 		retval = -EPERM;
 		goto out_err;
 	}
 	if (copy_from_user(&f_handle, ufh, sizeof(struct file_handle))) {
 		retval = -EFAULT;
 		goto out_err;
 	}
 	if ((f_handle.handle_bytes > MAX_HANDLE_SZ) ||
 	    (f_handle.handle_bytes == 0)) {
 		retval = -EINVAL;
 		goto out_err;
 	}
 	handle = kmalloc(sizeof(struct file_handle) + f_handle.handle_bytes,
 			 GFP_KERNEL);
 	if (!handle) {
 		retval = -ENOMEM;
 		goto out_err;
 	}
 	/* copy the full handle */
 	*handle = f_handle;
 	if (copy_from_user(&handle->f_handle,
 			   &ufh->f_handle,
 			   f_handle.handle_bytes)) {
 		retval = -EFAULT;
 		goto out_handle;
 	}

 	retval = do_handle_to_path(mountdirfd, handle, path);

 out_handle:
 	kfree(handle);
 out_err:
 	return retval;
 }

 static long do_handle_open(int mountdirfd, struct file_handle __user *ufh,
 			   int open_flag)
 {
 	long retval = 0;
 	struct path path;
 	struct file *file;
 	int fd;

 	retval = handle_to_path(mountdirfd, ufh, &path);
 	if (retval)
 		return retval;

 	fd = get_unused_fd_flags(open_flag);
 	if (fd < 0) {
 		path_put(&path);
 		return fd;
 	}
 	file = file_open_root(path.dentry, path.mnt, "", open_flag, 0);
 	if (IS_ERR(file)) {
 		put_unused_fd(fd);
 		retval =  PTR_ERR(file);
 	} else {
 		retval = fd;
 		fsnotify_open(file);
 		fd_install(fd, file);
 	}
 	path_put(&path);
 	return retval;
 }

 /**
  * sys_open_by_handle_at: Open the file handle
  * @mountdirfd: directory file descriptor
  * @handle: file handle to be opened
  * @flags: open flags.
  *
  * @mountdirfd indicate the directory file descriptor
  * of the mount point. file handle is decoded relative
  * to the vfsmount pointed by the @mountdirfd. @flags
  * value is same as the open(2) flags.
  */
 SYSCALL_DEFINE3(open_by_handle_at, int, mountdirfd,
 		struct file_handle __user *, handle,
 		int, flags)
 {
 	long ret;

 	if (force_o_largefile())
 		flags |= O_LARGEFILE;

 	ret = do_handle_open(mountdirfd, handle, flags);
 	return ret;
 }

 #ifdef CONFIG_COMPAT
 /*
  * Exactly like fs/open.c:sys_open_by_handle_at(), except that it
  * doesn't set the O_LARGEFILE flag.
  */
 COMPAT_SYSCALL_DEFINE3(open_by_handle_at, int, mountdirfd,
 			     struct file_handle __user *, handle, int, flags)
 {
 	return do_handle_open(mountdirfd, handle, flags);
 }
 #endif
	// SPDX-License-Identifier: GPL-2.0
	#include <linux/syscalls.h>
	#include <linux/slab.h>
	#include <linux/fs.h>
	#include <linux/file.h>
	#include <linux/mount.h>
	#include <linux/namei.h>
	#include <linux/exportfs.h>
	#include <linux/fs_struct.h>
	#include <linux/fsnotify.h>
	#include <linux/personality.h>
	#include <linux/uaccess.h>
	#include <linux/compat.h>
	#include "internal.h"
	#include "mount.h"

	static long do_sys_name_to_handle(struct path *path,
	struct file_handle __user *ufh,
	int __user *mnt_id)
	{
	long retval;
	struct file_handle f_handle;
	int handle_dwords, handle_bytes;
	struct file_handle *handle = NULL;

	/*
	* We need to make sure whether the file system
	* support decoding of the file handle
	*/
	if (!path->dentry->d_sb->s_export_op \|\|
	!path->dentry->d_sb->s_export_op->fh_to_dentry)
	return -EOPNOTSUPP;

	if (copy_from_user(&f_handle, ufh, sizeof(struct file_handle)))
	return -EFAULT;

	if (f_handle.handle_bytes > MAX_HANDLE_SZ)
	return -EINVAL;

	handle = kzalloc(sizeof(struct file_handle) + f_handle.handle_bytes,
	GFP_KERNEL);
	if (!handle)
	return -ENOMEM;

	/* convert handle size to multiple of sizeof(u32) */
	handle_dwords = f_handle.handle_bytes >> 2;

	/* we ask for a non connected handle */
	retval = exportfs_encode_fh(path->dentry,
	(struct fid *)handle->f_handle,
	&handle_dwords, 0);
	handle->handle_type = retval;
	/* convert handle size to bytes */
	handle_bytes = handle_dwords * sizeof(u32);
	handle->handle_bytes = handle_bytes;
	if ((handle->handle_bytes > f_handle.handle_bytes) \|\|
	(retval == FILEID_INVALID) \|\| (retval == -ENOSPC)) {
	/* As per old exportfs_encode_fh documentation
	* we could return ENOSPC to indicate overflow
	* But file system returned 255 always. So handle
	* both the values
	*/
	/*
	* set the handle size to zero so we copy only
	* non variable part of the file_handle
	*/
	handle_bytes = 0;
	retval = -EOVERFLOW;
	} else
	retval = 0;
	/* copy the mount id */
	if (put_user(real_mount(path->mnt)->mnt_id, mnt_id) \|\|
	copy_to_user(ufh, handle,
	sizeof(struct file_handle) + handle_bytes))
	retval = -EFAULT;
	kfree(handle);
	return retval;
	}

	/**
	* sys_name_to_handle_at: convert name to handle
	* @dfd: directory relative to which name is interpreted if not absolute
	* @name: name that should be converted to handle.
	* @handle: resulting file handle
	* @mnt_id: mount id of the file system containing the file
	* @flag: flag value to indicate whether to follow symlink or not
	*
	* @handle->handle_size indicate the space available to store the
	* variable part of the file handle in bytes. If there is not
	* enough space, the field is updated to return the minimum
	* value required.
	*/
	SYSCALL_DEFINE5(name_to_handle_at, int, dfd, const char __user *, name,
	struct file_handle __user , handle, int __user , mnt_id,
	int, flag)
	{
	struct path path;
	int lookup_flags;
	int err;

	if ((flag & ~(AT_SYMLINK_FOLLOW \| AT_EMPTY_PATH)) != 0)
	return -EINVAL;

	lookup_flags = (flag & AT_SYMLINK_FOLLOW) ? LOOKUP_FOLLOW : 0;
	if (flag & AT_EMPTY_PATH)
	lookup_flags \|= LOOKUP_EMPTY;
	err = user_path_at(dfd, name, lookup_flags, &path);
	if (!err) {
	err = do_sys_name_to_handle(&path, handle, mnt_id);
	path_put(&path);
	}
	return err;
	}

	static struct vfsmount *get_vfsmount_from_fd(int fd)
	{
	struct vfsmount *mnt;

	if (fd == AT_FDCWD) {
	struct fs_struct *fs = current->fs;
	spin_lock(&fs->lock);
	mnt = mntget(fs->pwd.mnt);
	spin_unlock(&fs->lock);
	} else {
	struct fd f = fdget(fd);
	if (!f.file)
	return ERR_PTR(-EBADF);
	mnt = mntget(f.file->f_path.mnt);
	fdput(f);
	}
	return mnt;
	}

	static int vfs_dentry_acceptable(void context, struct dentry dentry)
	{
	return 1;
	}

	static int do_handle_to_path(int mountdirfd, struct file_handle *handle,
	struct path *path)
	{
	int retval = 0;
	int handle_dwords;

	path->mnt = get_vfsmount_from_fd(mountdirfd);
	if (IS_ERR(path->mnt)) {
	retval = PTR_ERR(path->mnt);
	goto out_err;
	}
	/* change the handle size to multiple of sizeof(u32) */
	handle_dwords = handle->handle_bytes >> 2;
	path->dentry = exportfs_decode_fh(path->mnt,
	(struct fid *)handle->f_handle,
	handle_dwords, handle->handle_type,
	vfs_dentry_acceptable, NULL);
	if (IS_ERR(path->dentry)) {
	retval = PTR_ERR(path->dentry);
	goto out_mnt;
	}
	return 0;
	out_mnt:
	mntput(path->mnt);
	out_err:
	return retval;
	}

	static int handle_to_path(int mountdirfd, struct file_handle __user *ufh,
	struct path *path)
	{
	int retval = 0;
	struct file_handle f_handle;
	struct file_handle *handle = NULL;

	/*
	* With handle we don't look at the execute bit on the
	* the directory. Ideally we would like CAP_DAC_SEARCH.
	* But we don't have that
	*/
	if (!capable(CAP_DAC_READ_SEARCH)) {
	retval = -EPERM;
	goto out_err;
	}
	if (copy_from_user(&f_handle, ufh, sizeof(struct file_handle))) {
	retval = -EFAULT;
	goto out_err;
	}
	if ((f_handle.handle_bytes > MAX_HANDLE_SZ) \|\|
	(f_handle.handle_bytes == 0)) {
	retval = -EINVAL;
	goto out_err;
	}
	handle = kmalloc(sizeof(struct file_handle) + f_handle.handle_bytes,
	GFP_KERNEL);
	if (!handle) {
	retval = -ENOMEM;
	goto out_err;
	}
	/* copy the full handle */
	*handle = f_handle;
	if (copy_from_user(&handle->f_handle,
	&ufh->f_handle,
	f_handle.handle_bytes)) {
	retval = -EFAULT;
	goto out_handle;
	}

	retval = do_handle_to_path(mountdirfd, handle, path);

	out_handle:
	kfree(handle);
	out_err:
	return retval;
	}

	static long do_handle_open(int mountdirfd, struct file_handle __user *ufh,
	int open_flag)
	{
	long retval = 0;
	struct path path;
	struct file *file;
	int fd;

	retval = handle_to_path(mountdirfd, ufh, &path);
	if (retval)
	return retval;

	fd = get_unused_fd_flags(open_flag);
	if (fd < 0) {
	path_put(&path);
	return fd;
	}
	file = file_open_root(path.dentry, path.mnt, "", open_flag, 0);
	if (IS_ERR(file)) {
	put_unused_fd(fd);
	retval = PTR_ERR(file);
	} else {
	retval = fd;
	fsnotify_open(file);
	fd_install(fd, file);
	}
	path_put(&path);
	return retval;
	}

	/**
	* sys_open_by_handle_at: Open the file handle
	* @mountdirfd: directory file descriptor
	* @handle: file handle to be opened
	* @flags: open flags.
	*
	* @mountdirfd indicate the directory file descriptor
	* of the mount point. file handle is decoded relative
	* to the vfsmount pointed by the @mountdirfd. @flags
	* value is same as the open(2) flags.
	*/
	SYSCALL_DEFINE3(open_by_handle_at, int, mountdirfd,
	struct file_handle __user *, handle,
	int, flags)
	{
	long ret;

	if (force_o_largefile())
	flags \|= O_LARGEFILE;

	ret = do_handle_open(mountdirfd, handle, flags);
	return ret;
	}

	#ifdef CONFIG_COMPAT
	/*
	* Exactly like fs/open.c:sys_open_by_handle_at(), except that it
	* doesn't set the O_LARGEFILE flag.
	*/
	COMPAT_SYSCALL_DEFINE3(open_by_handle_at, int, mountdirfd,
	struct file_handle __user *, handle, int, flags)
	{
	return do_handle_open(mountdirfd, handle, flags);
	}
	#endif