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Commit becfd1f3 authored by Aneesh Kumar K.V's avatar Aneesh Kumar K.V Committed by Al Viro
Browse files

vfs: Add open by file handle support 



[AV: duplicate of open() guts removed; file_open_root() used instead]

Signed-off-by: default avatarAneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
parent 990d6c2d

fs/compat.c

+13 −0
Original line number Diff line number Diff line
@@ -2284,3 +2284,16 @@ asmlinkage long compat_sys_timerfd_gettime(int ufd, 
}



#endif /* CONFIG_TIMERFD */



#ifdef CONFIG_FHANDLE

/*

 * Exactly like fs/open.c:sys_open_by_handle_at(), except that it

 * doesn't set the O_LARGEFILE flag.

 */

asmlinkage long

compat_sys_open_by_handle_at(int mountdirfd,

			     struct file_handle __user *handle, int flags)

{

	return do_handle_open(mountdirfd, handle, flags);

}

#endif

fs/exportfs/expfs.c

+2 −0
Original line number Diff line number Diff line
@@ -374,6 +374,8 @@ struct dentry *exportfs_decode_fh(struct vfsmount *mnt, struct fid *fid, 
	/*

	 * Try to get any dentry for the given file handle from the filesystem.

	 */

	if (!nop || !nop->fh_to_dentry)

		return ERR_PTR(-ESTALE);

	result = nop->fh_to_dentry(mnt->mnt_sb, fid, fh_len, fileid_type);

	if (!result)

		result = ERR_PTR(-ESTALE);

fs/fhandle.c

+158 −0
Original line number Diff line number Diff line
@@ -5,6 +5,8 @@ 
#include <linux/mount.h>

#include <linux/namei.h>

#include <linux/exportfs.h>

#include <linux/fs_struct.h>

#include <linux/fsnotify.h>

#include <asm/uaccess.h>

#include "internal.h"
@@ -105,3 +107,159 @@ SYSCALL_DEFINE5(name_to_handle_at, int, dfd, const char __user *, name, 
	}

	return err;

}



static struct vfsmount *get_vfsmount_from_fd(int fd)

{

	struct path path;



	if (fd == AT_FDCWD) {

		struct fs_struct *fs = current->fs;

		spin_lock(&fs->lock);

		path = fs->pwd;

		mntget(path.mnt);

		spin_unlock(&fs->lock);

	} else {

		int fput_needed;

		struct file *file = fget_light(fd, &fput_needed);

		if (!file)

			return ERR_PTR(-EBADF);

		path = file->f_path;

		mntget(path.mnt);

		fput_light(file, fput_needed);

	}

	return path.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 */

	if (copy_from_user(handle, ufh,

			   sizeof(struct file_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;

}



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);

	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

 * @flag: 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;

}

fs/internal.h

+3 −0
Original line number Diff line number Diff line
@@ -117,6 +117,9 @@ extern struct file *do_filp_open(int dfd, const char *pathname, 
extern struct file *do_file_open_root(struct dentry *, struct vfsmount *,

		const char *, const struct open_flags *, int lookup_flags);



extern long do_handle_open(int mountdirfd,

			   struct file_handle __user *ufh, int open_flag);



/*

 * inode.c

 */

include/linux/syscalls.h

+3 −0
Original line number Diff line number Diff line
@@ -836,4 +836,7 @@ asmlinkage long sys_old_mmap(struct mmap_arg_struct __user *arg); 
asmlinkage long sys_name_to_handle_at(int dfd, const char __user *name,

				      struct file_handle __user *handle,

				      int __user *mnt_id, int flag);

asmlinkage long sys_open_by_handle_at(int mountdirfd,

				      struct file_handle __user *handle,

				      int flags);

#endif