Re: [PATCH v4 2/5] ima: use fs method to read integrity data

[Mimi Zohar <zohar@linux.vnet.ibm.com>]

On Tue, 2017-08-01 at 12:42 +0200, Jan Kara wrote:
> On Mon 31-07-17 15:08:53, Mimi Zohar wrote:
> > On Mon, 2017-07-31 at 09:01 +0200, Jan Kara wrote:
> > > On Wed 26-07-17 09:22:52, Mimi Zohar wrote:
> > > > From: Christoph Hellwig <hch@lst.de>
> > > > 
> > > > Add a new ->integrity_read file operation to read data for integrity
> > > > hash collection.  This is defined to be equivalent to ->read_iter,
> > > > except that it will be called with the i_rwsem held exclusively.
> > > 
> > > The patch looks mostly good to me.
> > 
> > Thanks!  Can I include your Ack-by?
> 
> After gfs2 & ocfs2 matters are settled...
> 
> > 
> > > Just one question: How did you select
> > > filesystems that implement .integrity_read method?
> > 
> > Initially I started out looking at the fs/.../Kconfig, but after
> > spending a while looking at the number of filesystems, I gave up and
> > asked Christoph (offline) where to begin.  I also compared the
> > measurement list from before and after the change and noticed some
> > missing file measurements (eg. ramfs, shmem, efivarfs).
> 
> OK, makes sense.
> 
> > > And I still maintain
> > > that it would be IMHO safer to not pretend we support IMA on gfs2 and ocfs2
> > > unless you either make sure they are mounted in local-only mode or figure
> > > out how to deal with proper cluster locking.
> > 
> > Agreed.  With patch 1/7 "ima: always measure and audit files in
> > policy", at least a file measurement containing a 0x00's hash value
> > will be included in the IMA measurement list.
> 
> Well, but for OCFS2 and GFS2 you have defined .integrity_read methods to
> generic_file_read_iter() and they will return data so IMA will think
> everything is fine. Just they may crash while doing so or return bogus data
> due to insufficient locking generic_file_read_iter() provides. So my
> suggestion is to just not provide .integrity_read for these two filesystems
> until you (or someone else) can figure out how to do that safely.

Sorry my explanation above wasn't clear.  Yes, I'll remove the
integrity_read method definitions for gfs2 and ocfs2.  As a result of
removing the integrity_read operation, the measurement list will
contain 0x00 hash values, instead of the real file hash.

Mimi 


> 
> > > > Signed-off-by: Christoph Hellwig <hch@lst.de>
> > > > Cc: Matthew Garrett <matthew.garrett@nebula.com>
> > > > Cc: Jan Kara <jack@suse.com>
> > > > Cc: "Theodore Ts'o" <tytso@mit.edu>
> > > > Cc: Andreas Dilger <adilger.kernel@dilger.ca>
> > > > Cc: Jaegeuk Kim <jaegeuk@kernel.org>
> > > > Cc: Chao Yu <yuchao0@huawei.com>
> > > > Cc: Steven Whitehouse <swhiteho@redhat.com>
> > > > Cc: Bob Peterson <rpeterso@redhat.com>
> > > > Cc: David Woodhouse <dwmw2@infradead.org>
> > > > Cc: Dave Kleikamp <shaggy@kernel.org>
> > > > Cc: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
> > > > Cc: Mark Fasheh <mfasheh@versity.com>
> > > > Cc: Joel Becker <jlbec@evilplan.org>
> > > > Cc: Richard Weinberger <richard@nod.at>
> > > > Cc: "Darrick J. Wong" <darrick.wong@oracle.com>
> > > > Cc: Hugh Dickins <hughd@google.com>
> > > > Cc: Chris Mason <clm@fb.com>
> > > > Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com>
> > > > 
> > > > Changelog v4:
> > > > - define ext2/4 specific ->integrity_read functions.
> > > > - properly fail file open with O_DIRECT on filesystem not mounted
> > > > with "-o dax".
> > > > 
> > > > ---
> > > > Changelog v3:
> > > > - define simple_read_iter_from_buffer
> > > > - replace the existing efivarfs ->read method with ->read_iter method.
> > > > - squashed other fs definitions of ->integrity_read with this patch.
> > > > 
> > > > Changelog v2:
> > > > - change iovec to kvec
> > > > 
> > > > Changelog v1:
> > > > - update the patch description, removing the concept that the presence of
> > > > ->integrity_read indicates that the file system can support IMA. (Mimi)
> > > > 
> > > >  fs/btrfs/file.c           |  1 +
> > > >  fs/efivarfs/file.c        | 12 +++++++-----
> > > >  fs/ext2/file.c            | 17 +++++++++++++++++
> > > >  fs/ext4/file.c            | 23 +++++++++++++++++++++++
> > > >  fs/f2fs/file.c            |  1 +
> > > >  fs/gfs2/file.c            |  2 ++
> > > >  fs/jffs2/file.c           |  1 +
> > > >  fs/jfs/file.c             |  1 +
> > > >  fs/libfs.c                | 32 ++++++++++++++++++++++++++++++++
> > > >  fs/nilfs2/file.c          |  1 +
> > > >  fs/ocfs2/file.c           |  1 +
> > > >  fs/ramfs/file-mmu.c       |  1 +
> > > >  fs/ramfs/file-nommu.c     |  1 +
> > > >  fs/ubifs/file.c           |  1 +
> > > >  fs/xfs/xfs_file.c         | 21 +++++++++++++++++++++
> > > >  include/linux/fs.h        |  3 +++
> > > >  mm/shmem.c                |  1 +
> > > >  security/integrity/iint.c | 20 ++++++++++++++------
> > > >  18 files changed, 129 insertions(+), 11 deletions(-)
> > > > 
> > > > diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
> > > > index 9e75d8a39aac..2542dc66c85c 100644
> > > > --- a/fs/btrfs/file.c
> > > > +++ b/fs/btrfs/file.c
> > > > @@ -3125,6 +3125,7 @@ const struct file_operations btrfs_file_operations = {
> > > >  #endif
> > > >  	.clone_file_range = btrfs_clone_file_range,
> > > >  	.dedupe_file_range = btrfs_dedupe_file_range,
> > > > +	.integrity_read = generic_file_read_iter,
> > > >  };
> > > >  
> > > >  void btrfs_auto_defrag_exit(void)
> > > > diff --git a/fs/efivarfs/file.c b/fs/efivarfs/file.c
> > > > index 5f22e74bbade..17955a92a5b3 100644
> > > > --- a/fs/efivarfs/file.c
> > > > +++ b/fs/efivarfs/file.c
> > > > @@ -64,9 +64,10 @@ static ssize_t efivarfs_file_write(struct file *file,
> > > >  	return bytes;
> > > >  }
> > > >  
> > > > -static ssize_t efivarfs_file_read(struct file *file, char __user *userbuf,
> > > > -		size_t count, loff_t *ppos)
> > > > +static ssize_t efivarfs_file_read_iter(struct kiocb *iocb,
> > > > +				       struct iov_iter *iter)
> > > >  {
> > > > +	struct file *file = iocb->ki_filp;
> > > >  	struct efivar_entry *var = file->private_data;
> > > >  	unsigned long datasize = 0;
> > > >  	u32 attributes;
> > > > @@ -96,8 +97,8 @@ static ssize_t efivarfs_file_read(struct file *file, char __user *userbuf,
> > > >  		goto out_free;
> > > >  
> > > >  	memcpy(data, &attributes, sizeof(attributes));
> > > > -	size = simple_read_from_buffer(userbuf, count, ppos,
> > > > -				       data, datasize + sizeof(attributes));
> > > > +	size = simple_read_iter_from_buffer(iocb, iter, data,
> > > > +					    datasize + sizeof(attributes));
> > > >  out_free:
> > > >  	kfree(data);
> > > >  
> > > > @@ -174,8 +175,9 @@ efivarfs_file_ioctl(struct file *file, unsigned int cmd, unsigned long p)
> > > >  
> > > >  const struct file_operations efivarfs_file_operations = {
> > > >  	.open	= simple_open,
> > > > -	.read	= efivarfs_file_read,
> > > > +	.read_iter = efivarfs_file_read_iter,
> > > >  	.write	= efivarfs_file_write,
> > > >  	.llseek	= no_llseek,
> > > >  	.unlocked_ioctl = efivarfs_file_ioctl,
> > > > +	.integrity_read	= efivarfs_file_read_iter,
> > > >  };
> > > > diff --git a/fs/ext2/file.c b/fs/ext2/file.c
> > > > index d34d32bdc944..111069de1973 100644
> > > > --- a/fs/ext2/file.c
> > > > +++ b/fs/ext2/file.c
> > > > @@ -192,6 +192,22 @@ static ssize_t ext2_file_read_iter(struct kiocb *iocb, struct iov_iter *to)
> > > >  	return generic_file_read_iter(iocb, to);
> > > >  }
> > > >  
> > > > +static ssize_t ext2_file_integrity_read_iter(struct kiocb *iocb,
> > > > +					     struct iov_iter *to)
> > > > +{
> > > > +	struct inode *inode = file_inode(iocb->ki_filp);
> > > > +
> > > > +	lockdep_assert_held(&inode->i_rwsem);
> > > > +#ifdef CONFIG_FS_DAX
> > > > +	if (!iov_iter_count(to))
> > > > +		return 0; /* skip atime */
> > > > +
> > > > +	if (IS_DAX(iocb->ki_filp->f_mapping->host))
> > > > +		return dax_iomap_rw(iocb, to, &ext2_iomap_ops);
> > > > +#endif
> > > > +	return generic_file_read_iter(iocb, to);
> > > > +}
> > > > +
> > > >  static ssize_t ext2_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
> > > >  {
> > > >  #ifdef CONFIG_FS_DAX
> > > > @@ -216,6 +232,7 @@ const struct file_operations ext2_file_operations = {
> > > >  	.get_unmapped_area = thp_get_unmapped_area,
> > > >  	.splice_read	= generic_file_splice_read,
> > > >  	.splice_write	= iter_file_splice_write,
> > > > +	.integrity_read	= ext2_file_integrity_read_iter,
> > > >  };
> > > >  
> > > >  const struct inode_operations ext2_file_inode_operations = {
> > > > diff --git a/fs/ext4/file.c b/fs/ext4/file.c
> > > > index 58294c9a7e1d..cb423fff935f 100644
> > > > --- a/fs/ext4/file.c
> > > > +++ b/fs/ext4/file.c
> > > > @@ -74,6 +74,28 @@ static ssize_t ext4_file_read_iter(struct kiocb *iocb, struct iov_iter *to)
> > > >  	return generic_file_read_iter(iocb, to);
> > > >  }
> > > >  
> > > > +static ssize_t ext4_file_integrity_read_iter(struct kiocb *iocb,
> > > > +					     struct iov_iter *to)
> > > > +{
> > > > +	struct inode *inode = file_inode(iocb->ki_filp);
> > > > +	int o_direct = iocb->ki_flags & IOCB_DIRECT;
> > > > +
> > > > +	lockdep_assert_held(&inode->i_rwsem);
> > > > +	if (unlikely(ext4_forced_shutdown(EXT4_SB(inode->i_sb))))
> > > > +		return -EIO;
> > > > +
> > > > +	if (!iov_iter_count(to))
> > > > +		return 0; /* skip atime */
> > > > +
> > > > +#ifdef CONFIG_FS_DAX
> > > > +	if (IS_DAX(inode))
> > > > +		return dax_iomap_rw(iocb, to, &ext4_iomap_ops);
> > > > +#endif
> > > > +	if (o_direct)
> > > > +		return -EINVAL;
> > > > +	return generic_file_read_iter(iocb, to);
> > > > +}
> > > > +
> > > >  /*
> > > >   * Called when an inode is released. Note that this is different
> > > >   * from ext4_file_open: open gets called at every open, but release
> > > > @@ -747,6 +769,7 @@ const struct file_operations ext4_file_operations = {
> > > >  	.splice_read	= generic_file_splice_read,
> > > >  	.splice_write	= iter_file_splice_write,
> > > >  	.fallocate	= ext4_fallocate,
> > > > +	.integrity_read	= ext4_file_integrity_read_iter,
> > > >  };
> > > >  
> > > >  const struct inode_operations ext4_file_inode_operations = {
> > > > diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
> > > > index 2706130c261b..82ea81da0b2d 100644
> > > > --- a/fs/f2fs/file.c
> > > > +++ b/fs/f2fs/file.c
> > > > @@ -2514,4 +2514,5 @@ const struct file_operations f2fs_file_operations = {
> > > >  #endif
> > > >  	.splice_read	= generic_file_splice_read,
> > > >  	.splice_write	= iter_file_splice_write,
> > > > +	.integrity_read	= generic_file_read_iter,
> > > >  };
> > > > diff --git a/fs/gfs2/file.c b/fs/gfs2/file.c
> > > > index c2062a108d19..9b49d09ba180 100644
> > > > --- a/fs/gfs2/file.c
> > > > +++ b/fs/gfs2/file.c
> > > > @@ -1124,6 +1124,7 @@ const struct file_operations gfs2_file_fops = {
> > > >  	.splice_write	= gfs2_file_splice_write,
> > > >  	.setlease	= simple_nosetlease,
> > > >  	.fallocate	= gfs2_fallocate,
> > > > +	.integrity_read	= generic_file_read_iter,
> > > >  };
> > > >  
> > > >  const struct file_operations gfs2_dir_fops = {
> > > > @@ -1152,6 +1153,7 @@ const struct file_operations gfs2_file_fops_nolock = {
> > > >  	.splice_write	= gfs2_file_splice_write,
> > > >  	.setlease	= generic_setlease,
> > > >  	.fallocate	= gfs2_fallocate,
> > > > +	.integrity_read	= generic_file_read_iter,
> > > >  };
> > > >  
> > > >  const struct file_operations gfs2_dir_fops_nolock = {
> > > > diff --git a/fs/jffs2/file.c b/fs/jffs2/file.c
> > > > index c12476e309c6..5a63034cccf5 100644
> > > > --- a/fs/jffs2/file.c
> > > > +++ b/fs/jffs2/file.c
> > > > @@ -57,6 +57,7 @@ const struct file_operations jffs2_file_operations =
> > > >  	.mmap =		generic_file_readonly_mmap,
> > > >  	.fsync =	jffs2_fsync,
> > > >  	.splice_read =	generic_file_splice_read,
> > > > +	.integrity_read = generic_file_read_iter,
> > > >  };
> > > >  
> > > >  /* jffs2_file_inode_operations */
> > > > diff --git a/fs/jfs/file.c b/fs/jfs/file.c
> > > > index 739492c7a3fd..423512a810e4 100644
> > > > --- a/fs/jfs/file.c
> > > > +++ b/fs/jfs/file.c
> > > > @@ -162,4 +162,5 @@ const struct file_operations jfs_file_operations = {
> > > >  #ifdef CONFIG_COMPAT
> > > >  	.compat_ioctl	= jfs_compat_ioctl,
> > > >  #endif
> > > > +	.integrity_read	= generic_file_read_iter,
> > > >  };
> > > > diff --git a/fs/libfs.c b/fs/libfs.c
> > > > index 3aabe553fc45..99333264a0a7 100644
> > > > --- a/fs/libfs.c
> > > > +++ b/fs/libfs.c
> > > > @@ -16,6 +16,7 @@
> > > >  #include <linux/exportfs.h>
> > > >  #include <linux/writeback.h>
> > > >  #include <linux/buffer_head.h> /* sync_mapping_buffers */
> > > > +#include <linux/uio.h>
> > > >  
> > > >  #include <linux/uaccess.h>
> > > >  
> > > > @@ -676,6 +677,37 @@ ssize_t simple_write_to_buffer(void *to, size_t available, loff_t *ppos,
> > > >  EXPORT_SYMBOL(simple_write_to_buffer);
> > > >  
> > > >  /**
> > > > + * simple_read_iter_from_buffer - copy data from the buffer to user space
> > > > + * @iocb: struct containing the file, the current position and other info
> > > > + * @to: the user space buffer to read to
> > > > + * @from: the buffer to read from
> > > > + * @available: the size of the buffer
> > > > + *
> > > > + * The simple_read_iter_from_buffer() function reads up to @available bytes
> > > > + * from the current buffer into the user space buffer.
> > > > + *
> > > > + * On success, the current buffer offset is advanced by the number of bytes
> > > > + * read, or a negative value is returned on error.
> > > > + **/
> > > > +ssize_t simple_read_iter_from_buffer(struct kiocb *iocb, struct iov_iter *to,
> > > > +                                const void *from, size_t available)
> > > > +{
> > > > +	loff_t pos = iocb->ki_pos;
> > > > +	size_t ret;
> > > > +
> > > > +	if (pos < 0)
> > > > +		return -EINVAL;
> > > > +	if (pos >= available)
> > > > +		return 0;
> > > > +	ret = copy_to_iter(from + pos, available - pos, to);
> > > > +	if (!ret && iov_iter_count(to))
> > > > +		return -EFAULT;
> > > > +	iocb->ki_pos = pos + ret;
> > > > +	return ret;
> > > > +}
> > > > +EXPORT_SYMBOL(simple_read_iter_from_buffer);
> > > > +
> > > > +/**
> > > >   * memory_read_from_buffer - copy data from the buffer
> > > >   * @to: the kernel space buffer to read to
> > > >   * @count: the maximum number of bytes to read
> > > > diff --git a/fs/nilfs2/file.c b/fs/nilfs2/file.c
> > > > index c5fa3dee72fc..55e058ac487f 100644
> > > > --- a/fs/nilfs2/file.c
> > > > +++ b/fs/nilfs2/file.c
> > > > @@ -150,6 +150,7 @@ const struct file_operations nilfs_file_operations = {
> > > >  	/* .release	= nilfs_release_file, */
> > > >  	.fsync		= nilfs_sync_file,
> > > >  	.splice_read	= generic_file_splice_read,
> > > > +	.integrity_read	= generic_file_read_iter,
> > > >  };
> > > >  
> > > >  const struct inode_operations nilfs_file_inode_operations = {
> > > > diff --git a/fs/ocfs2/file.c b/fs/ocfs2/file.c
> > > > index bfeb647459d9..2832a7c92acd 100644
> > > > --- a/fs/ocfs2/file.c
> > > > +++ b/fs/ocfs2/file.c
> > > > @@ -2536,6 +2536,7 @@ const struct file_operations ocfs2_fops = {
> > > >  	.fallocate	= ocfs2_fallocate,
> > > >  	.clone_file_range = ocfs2_file_clone_range,
> > > >  	.dedupe_file_range = ocfs2_file_dedupe_range,
> > > > +	.integrity_read	= ocfs2_file_read_iter,
> > > >  };
> > > >  
> > > >  const struct file_operations ocfs2_dops = {
> > > > diff --git a/fs/ramfs/file-mmu.c b/fs/ramfs/file-mmu.c
> > > > index 12af0490322f..4f24d1b589b1 100644
> > > > --- a/fs/ramfs/file-mmu.c
> > > > +++ b/fs/ramfs/file-mmu.c
> > > > @@ -47,6 +47,7 @@ const struct file_operations ramfs_file_operations = {
> > > >  	.splice_write	= iter_file_splice_write,
> > > >  	.llseek		= generic_file_llseek,
> > > >  	.get_unmapped_area	= ramfs_mmu_get_unmapped_area,
> > > > +	.integrity_read	= generic_file_read_iter,
> > > >  };
> > > >  
> > > >  const struct inode_operations ramfs_file_inode_operations = {
> > > > diff --git a/fs/ramfs/file-nommu.c b/fs/ramfs/file-nommu.c
> > > > index 2ef7ce75c062..5ee704fa84e0 100644
> > > > --- a/fs/ramfs/file-nommu.c
> > > > +++ b/fs/ramfs/file-nommu.c
> > > > @@ -50,6 +50,7 @@ const struct file_operations ramfs_file_operations = {
> > > >  	.splice_read		= generic_file_splice_read,
> > > >  	.splice_write		= iter_file_splice_write,
> > > >  	.llseek			= generic_file_llseek,
> > > > +	.integrity_read		= generic_file_read_iter,
> > > >  };
> > > >  
> > > >  const struct inode_operations ramfs_file_inode_operations = {
> > > > diff --git a/fs/ubifs/file.c b/fs/ubifs/file.c
> > > > index 8cad0b19b404..5e52a315e18b 100644
> > > > --- a/fs/ubifs/file.c
> > > > +++ b/fs/ubifs/file.c
> > > > @@ -1747,4 +1747,5 @@ const struct file_operations ubifs_file_operations = {
> > > >  #ifdef CONFIG_COMPAT
> > > >  	.compat_ioctl   = ubifs_compat_ioctl,
> > > >  #endif
> > > > +	.integrity_read = generic_file_read_iter,
> > > >  };
> > > > diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
> > > > index c4893e226fd8..0a6704b563d6 100644
> > > > --- a/fs/xfs/xfs_file.c
> > > > +++ b/fs/xfs/xfs_file.c
> > > > @@ -292,6 +292,26 @@ xfs_file_read_iter(
> > > >  	return ret;
> > > >  }
> > > >  
> > > > +static ssize_t
> > > > +xfs_integrity_read(
> > > > +	struct kiocb		*iocb,
> > > > +	struct iov_iter		*to)
> > > > +{
> > > > +	struct inode		*inode = file_inode(iocb->ki_filp);
> > > > +	struct xfs_mount	*mp = XFS_I(inode)->i_mount;
> > > > +
> > > > +	lockdep_assert_held(&inode->i_rwsem);
> > > > +
> > > > +	XFS_STATS_INC(mp, xs_read_calls);
> > > > +
> > > > +	if (XFS_FORCED_SHUTDOWN(mp))
> > > > +		return -EIO;
> > > > +
> > > > +	if (IS_DAX(inode))
> > > > +		return dax_iomap_rw(iocb, to, &xfs_iomap_ops);
> > > > +	return generic_file_read_iter(iocb, to);
> > > > +}
> > > > +
> > > >  /*
> > > >   * Zero any on disk space between the current EOF and the new, larger EOF.
> > > >   *
> > > > @@ -1175,6 +1195,7 @@ const struct file_operations xfs_file_operations = {
> > > >  	.fallocate	= xfs_file_fallocate,
> > > >  	.clone_file_range = xfs_file_clone_range,
> > > >  	.dedupe_file_range = xfs_file_dedupe_range,
> > > > +	.integrity_read	= xfs_integrity_read,
> > > >  };
> > > >  
> > > >  const struct file_operations xfs_dir_file_operations = {
> > > > diff --git a/include/linux/fs.h b/include/linux/fs.h
> > > > index 6e1fd5d21248..8d0d10e1dd93 100644
> > > > --- a/include/linux/fs.h
> > > > +++ b/include/linux/fs.h
> > > > @@ -1699,6 +1699,7 @@ struct file_operations {
> > > >  			u64);
> > > >  	ssize_t (*dedupe_file_range)(struct file *, u64, u64, struct file *,
> > > >  			u64);
> > > > +	ssize_t (*integrity_read)(struct kiocb *, struct iov_iter *);
> > > >  } __randomize_layout;
> > > >  
> > > >  struct inode_operations {
> > > > @@ -3097,6 +3098,8 @@ extern void simple_release_fs(struct vfsmount **mount, int *count);
> > > >  
> > > >  extern ssize_t simple_read_from_buffer(void __user *to, size_t count,
> > > >  			loff_t *ppos, const void *from, size_t available);
> > > > +extern ssize_t simple_read_iter_from_buffer(struct kiocb *iocb,
> > > > +		struct iov_iter *to, const void *from, size_t available);
> > > >  extern ssize_t simple_write_to_buffer(void *to, size_t available, loff_t *ppos,
> > > >  		const void __user *from, size_t count);
> > > >  
> > > > diff --git a/mm/shmem.c b/mm/shmem.c
> > > > index b0aa6075d164..805d99011ca4 100644
> > > > --- a/mm/shmem.c
> > > > +++ b/mm/shmem.c
> > > > @@ -3849,6 +3849,7 @@ static const struct file_operations shmem_file_operations = {
> > > >  	.splice_read	= generic_file_splice_read,
> > > >  	.splice_write	= iter_file_splice_write,
> > > >  	.fallocate	= shmem_fallocate,
> > > > +	.integrity_read	= shmem_file_read_iter,
> > > >  #endif
> > > >  };
> > > >  
> > > > diff --git a/security/integrity/iint.c b/security/integrity/iint.c
> > > > index 6fc888ca468e..df04f35a1d40 100644
> > > > --- a/security/integrity/iint.c
> > > > +++ b/security/integrity/iint.c
> > > > @@ -21,6 +21,7 @@
> > > >  #include <linux/rbtree.h>
> > > >  #include <linux/file.h>
> > > >  #include <linux/uaccess.h>
> > > > +#include <linux/uio.h>
> > > >  #include "integrity.h"
> > > >  
> > > >  static struct rb_root integrity_iint_tree = RB_ROOT;
> > > > @@ -184,18 +185,25 @@ security_initcall(integrity_iintcache_init);
> > > >  int integrity_kernel_read(struct file *file, loff_t offset,
> > > >  			  void *addr, unsigned long count)
> > > >  {
> > > > -	mm_segment_t old_fs;
> > > > -	char __user *buf = (char __user *)addr;
> > > > +	struct inode *inode = file_inode(file);
> > > > +	struct kvec iov = { .iov_base = addr, .iov_len = count };
> > > > +	struct kiocb kiocb;
> > > > +	struct iov_iter iter;
> > > >  	ssize_t ret;
> > > >  
> > > > +	lockdep_assert_held(&inode->i_rwsem);
> > > > +
> > > >  	if (!(file->f_mode & FMODE_READ))
> > > >  		return -EBADF;
> > > > +	if (!file->f_op->integrity_read)
> > > > +		return -EBADF;
> > > >  
> > > > -	old_fs = get_fs();
> > > > -	set_fs(get_ds());
> > > > -	ret = __vfs_read(file, buf, count, &offset);
> > > > -	set_fs(old_fs);
> > > > +	init_sync_kiocb(&kiocb, file);
> > > > +	kiocb.ki_pos = offset;
> > > > +	iov_iter_kvec(&iter, READ | ITER_KVEC, &iov, 1, count);
> > > >  
> > > > +	ret = file->f_op->integrity_read(&kiocb, &iter);
> > > > +	BUG_ON(ret == -EIOCBQUEUED);
> > > >  	return ret;
> > > >  }
> > > >  
> > > > -- 
> > > > 2.7.4
> > > > 
> > > > 
> >