1 files changed, 755 insertions, 0 deletions

diff --git a/fs/overlayfs/file.c b/fs/overlayfs/file.c
new file mode 100644
index 0000000000..8be4dc050d
--- /dev/null
+++ b/fs/overlayfs/file.c
@@ -0,0 +1,755 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2017 Red Hat, Inc.
+ */
+
+#include <linux/cred.h>
+#include <linux/file.h>
+#include <linux/mount.h>
+#include <linux/xattr.h>
+#include <linux/uio.h>
+#include <linux/uaccess.h>
+#include <linux/splice.h>
+#include <linux/security.h>
+#include <linux/mm.h>
+#include <linux/fs.h>
+#include "overlayfs.h"
+
+struct ovl_aio_req {
+	struct kiocb iocb;
+	refcount_t ref;
+	struct kiocb *orig_iocb;
+};
+
+static struct kmem_cache *ovl_aio_request_cachep;
+
+static char ovl_whatisit(struct inode *inode, struct inode *realinode)
+{
+	if (realinode != ovl_inode_upper(inode))
+		return 'l';
+	if (ovl_has_upperdata(inode))
+		return 'u';
+	else
+		return 'm';
+}
+
+/* No atime modification on underlying */
+#define OVL_OPEN_FLAGS (O_NOATIME)
+
+static struct file *ovl_open_realfile(const struct file *file,
+				      const struct path *realpath)
+{
+	struct inode *realinode = d_inode(realpath->dentry);
+	struct inode *inode = file_inode(file);
+	struct mnt_idmap *real_idmap;
+	struct file *realfile;
+	const struct cred *old_cred;
+	int flags = file->f_flags | OVL_OPEN_FLAGS;
+	int acc_mode = ACC_MODE(flags);
+	int err;
+
+	if (flags & O_APPEND)
+		acc_mode |= MAY_APPEND;
+
+	old_cred = ovl_override_creds(inode->i_sb);
+	real_idmap = mnt_idmap(realpath->mnt);
+	err = inode_permission(real_idmap, realinode, MAY_OPEN | acc_mode);
+	if (err) {
+		realfile = ERR_PTR(err);
+	} else {
+		if (!inode_owner_or_capable(real_idmap, realinode))
+			flags &= ~O_NOATIME;
+
+		realfile = backing_file_open(&file->f_path, flags, realpath,
+					     current_cred());
+	}
+	revert_creds(old_cred);
+
+	pr_debug("open(%p[%pD2/%c], 0%o) -> (%p, 0%o)\n",
+		 file, file, ovl_whatisit(inode, realinode), file->f_flags,
+		 realfile, IS_ERR(realfile) ? 0 : realfile->f_flags);
+
+	return realfile;
+}
+
+#define OVL_SETFL_MASK (O_APPEND | O_NONBLOCK | O_NDELAY | O_DIRECT)
+
+static int ovl_change_flags(struct file *file, unsigned int flags)
+{
+	struct inode *inode = file_inode(file);
+	int err;
+
+	flags &= OVL_SETFL_MASK;
+
+	if (((flags ^ file->f_flags) & O_APPEND) && IS_APPEND(inode))
+		return -EPERM;
+
+	if ((flags & O_DIRECT) && !(file->f_mode & FMODE_CAN_ODIRECT))
+		return -EINVAL;
+
+	if (file->f_op->check_flags) {
+		err = file->f_op->check_flags(flags);
+		if (err)
+			return err;
+	}
+
+	spin_lock(&file->f_lock);
+	file->f_flags = (file->f_flags & ~OVL_SETFL_MASK) | flags;
+	file->f_iocb_flags = iocb_flags(file);
+	spin_unlock(&file->f_lock);
+
+	return 0;
+}
+
+static int ovl_real_fdget_meta(const struct file *file, struct fd *real,
+			       bool allow_meta)
+{
+	struct dentry *dentry = file_dentry(file);
+	struct path realpath;
+	int err;
+
+	real->flags = 0;
+	real->file = file->private_data;
+
+	if (allow_meta) {
+		ovl_path_real(dentry, &realpath);
+	} else {
+		/* lazy lookup and verify of lowerdata */
+		err = ovl_verify_lowerdata(dentry);
+		if (err)
+			return err;
+
+		ovl_path_realdata(dentry, &realpath);
+	}
+	if (!realpath.dentry)
+		return -EIO;
+
+	/* Has it been copied up since we'd opened it? */
+	if (unlikely(file_inode(real->file) != d_inode(realpath.dentry))) {
+		real->flags = FDPUT_FPUT;
+		real->file = ovl_open_realfile(file, &realpath);
+
+		return PTR_ERR_OR_ZERO(real->file);
+	}
+
+	/* Did the flags change since open? */
+	if (unlikely((file->f_flags ^ real->file->f_flags) & ~OVL_OPEN_FLAGS))
+		return ovl_change_flags(real->file, file->f_flags);
+
+	return 0;
+}
+
+static int ovl_real_fdget(const struct file *file, struct fd *real)
+{
+	if (d_is_dir(file_dentry(file))) {
+		real->flags = 0;
+		real->file = ovl_dir_real_file(file, false);
+
+		return PTR_ERR_OR_ZERO(real->file);
+	}
+
+	return ovl_real_fdget_meta(file, real, false);
+}
+
+static int ovl_open(struct inode *inode, struct file *file)
+{
+	struct dentry *dentry = file_dentry(file);
+	struct file *realfile;
+	struct path realpath;
+	int err;
+
+	/* lazy lookup and verify lowerdata */
+	err = ovl_verify_lowerdata(dentry);
+	if (err)
+		return err;
+
+	err = ovl_maybe_copy_up(dentry, file->f_flags);
+	if (err)
+		return err;
+
+	/* No longer need these flags, so don't pass them on to underlying fs */
+	file->f_flags &= ~(O_CREAT | O_EXCL | O_NOCTTY | O_TRUNC);
+
+	ovl_path_realdata(dentry, &realpath);
+	if (!realpath.dentry)
+		return -EIO;
+
+	realfile = ovl_open_realfile(file, &realpath);
+	if (IS_ERR(realfile))
+		return PTR_ERR(realfile);
+
+	file->private_data = realfile;
+
+	return 0;
+}
+
+static int ovl_release(struct inode *inode, struct file *file)
+{
+	fput(file->private_data);
+
+	return 0;
+}
+
+static loff_t ovl_llseek(struct file *file, loff_t offset, int whence)
+{
+	struct inode *inode = file_inode(file);
+	struct fd real;
+	const struct cred *old_cred;
+	loff_t ret;
+
+	/*
+	 * The two special cases below do not need to involve real fs,
+	 * so we can optimizing concurrent callers.
+	 */
+	if (offset == 0) {
+		if (whence == SEEK_CUR)
+			return file->f_pos;
+
+		if (whence == SEEK_SET)
+			return vfs_setpos(file, 0, 0);
+	}
+
+	ret = ovl_real_fdget(file, &real);
+	if (ret)
+		return ret;
+
+	/*
+	 * Overlay file f_pos is the master copy that is preserved
+	 * through copy up and modified on read/write, but only real
+	 * fs knows how to SEEK_HOLE/SEEK_DATA and real fs may impose
+	 * limitations that are more strict than ->s_maxbytes for specific
+	 * files, so we use the real file to perform seeks.
+	 */
+	ovl_inode_lock(inode);
+	real.file->f_pos = file->f_pos;
+
+	old_cred = ovl_override_creds(inode->i_sb);
+	ret = vfs_llseek(real.file, offset, whence);
+	revert_creds(old_cred);
+
+	file->f_pos = real.file->f_pos;
+	ovl_inode_unlock(inode);
+
+	fdput(real);
+
+	return ret;
+}
+
+static void ovl_file_accessed(struct file *file)
+{
+	struct inode *inode, *upperinode;
+	struct timespec64 ctime, uctime;
+
+	if (file->f_flags & O_NOATIME)
+		return;
+
+	inode = file_inode(file);
+	upperinode = ovl_inode_upper(inode);
+
+	if (!upperinode)
+		return;
+
+	ctime = inode_get_ctime(inode);
+	uctime = inode_get_ctime(upperinode);
+	if ((!timespec64_equal(&inode->i_mtime, &upperinode->i_mtime) ||
+	     !timespec64_equal(&ctime, &uctime))) {
+		inode->i_mtime = upperinode->i_mtime;
+		inode_set_ctime_to_ts(inode, uctime);
+	}
+
+	touch_atime(&file->f_path);
+}
+
+static rwf_t ovl_iocb_to_rwf(int ifl)
+{
+	rwf_t flags = 0;
+
+	if (ifl & IOCB_NOWAIT)
+		flags |= RWF_NOWAIT;
+	if (ifl & IOCB_HIPRI)
+		flags |= RWF_HIPRI;
+	if (ifl & IOCB_DSYNC)
+		flags |= RWF_DSYNC;
+	if (ifl & IOCB_SYNC)
+		flags |= RWF_SYNC;
+
+	return flags;
+}
+
+static inline void ovl_aio_put(struct ovl_aio_req *aio_req)
+{
+	if (refcount_dec_and_test(&aio_req->ref)) {
+		fput(aio_req->iocb.ki_filp);
+		kmem_cache_free(ovl_aio_request_cachep, aio_req);
+	}
+}
+
+static void ovl_aio_cleanup_handler(struct ovl_aio_req *aio_req)
+{
+	struct kiocb *iocb = &aio_req->iocb;
+	struct kiocb *orig_iocb = aio_req->orig_iocb;
+
+	if (iocb->ki_flags & IOCB_WRITE) {
+		struct inode *inode = file_inode(orig_iocb->ki_filp);
+
+		kiocb_end_write(iocb);
+		ovl_copyattr(inode);
+	}
+
+	orig_iocb->ki_pos = iocb->ki_pos;
+	ovl_aio_put(aio_req);
+}
+
+static void ovl_aio_rw_complete(struct kiocb *iocb, long res)
+{
+	struct ovl_aio_req *aio_req = container_of(iocb,
+						   struct ovl_aio_req, iocb);
+	struct kiocb *orig_iocb = aio_req->orig_iocb;
+
+	ovl_aio_cleanup_handler(aio_req);
+	orig_iocb->ki_complete(orig_iocb, res);
+}
+
+static ssize_t ovl_read_iter(struct kiocb *iocb, struct iov_iter *iter)
+{
+	struct file *file = iocb->ki_filp;
+	struct fd real;
+	const struct cred *old_cred;
+	ssize_t ret;
+
+	if (!iov_iter_count(iter))
+		return 0;
+
+	ret = ovl_real_fdget(file, &real);
+	if (ret)
+		return ret;
+
+	ret = -EINVAL;
+	if (iocb->ki_flags & IOCB_DIRECT &&
+	    !(real.file->f_mode & FMODE_CAN_ODIRECT))
+		goto out_fdput;
+
+	old_cred = ovl_override_creds(file_inode(file)->i_sb);
+	if (is_sync_kiocb(iocb)) {
+		ret = vfs_iter_read(real.file, iter, &iocb->ki_pos,
+				    ovl_iocb_to_rwf(iocb->ki_flags));
+	} else {
+		struct ovl_aio_req *aio_req;
+
+		ret = -ENOMEM;
+		aio_req = kmem_cache_zalloc(ovl_aio_request_cachep, GFP_KERNEL);
+		if (!aio_req)
+			goto out;
+
+		aio_req->orig_iocb = iocb;
+		kiocb_clone(&aio_req->iocb, iocb, get_file(real.file));
+		aio_req->iocb.ki_complete = ovl_aio_rw_complete;
+		refcount_set(&aio_req->ref, 2);
+		ret = vfs_iocb_iter_read(real.file, &aio_req->iocb, iter);
+		ovl_aio_put(aio_req);
+		if (ret != -EIOCBQUEUED)
+			ovl_aio_cleanup_handler(aio_req);
+	}
+out:
+	revert_creds(old_cred);
+	ovl_file_accessed(file);
+out_fdput:
+	fdput(real);
+
+	return ret;
+}
+
+static ssize_t ovl_write_iter(struct kiocb *iocb, struct iov_iter *iter)
+{
+	struct file *file = iocb->ki_filp;
+	struct inode *inode = file_inode(file);
+	struct fd real;
+	const struct cred *old_cred;
+	ssize_t ret;
+	int ifl = iocb->ki_flags;
+
+	if (!iov_iter_count(iter))
+		return 0;
+
+	inode_lock(inode);
+	/* Update mode */
+	ovl_copyattr(inode);
+	ret = file_remove_privs(file);
+	if (ret)
+		goto out_unlock;
+
+	ret = ovl_real_fdget(file, &real);
+	if (ret)
+		goto out_unlock;
+
+	ret = -EINVAL;
+	if (iocb->ki_flags & IOCB_DIRECT &&
+	    !(real.file->f_mode & FMODE_CAN_ODIRECT))
+		goto out_fdput;
+
+	if (!ovl_should_sync(OVL_FS(inode->i_sb)))
+		ifl &= ~(IOCB_DSYNC | IOCB_SYNC);
+
+	/*
+	 * Overlayfs doesn't support deferred completions, don't copy
+	 * this property in case it is set by the issuer.
+	 */
+	ifl &= ~IOCB_DIO_CALLER_COMP;
+
+	old_cred = ovl_override_creds(file_inode(file)->i_sb);
+	if (is_sync_kiocb(iocb)) {
+		file_start_write(real.file);
+		ret = vfs_iter_write(real.file, iter, &iocb->ki_pos,
+				     ovl_iocb_to_rwf(ifl));
+		file_end_write(real.file);
+		/* Update size */
+		ovl_copyattr(inode);
+	} else {
+		struct ovl_aio_req *aio_req;
+
+		ret = -ENOMEM;
+		aio_req = kmem_cache_zalloc(ovl_aio_request_cachep, GFP_KERNEL);
+		if (!aio_req)
+			goto out;
+
+		aio_req->orig_iocb = iocb;
+		kiocb_clone(&aio_req->iocb, iocb, get_file(real.file));
+		aio_req->iocb.ki_flags = ifl;
+		aio_req->iocb.ki_complete = ovl_aio_rw_complete;
+		refcount_set(&aio_req->ref, 2);
+		kiocb_start_write(&aio_req->iocb);
+		ret = vfs_iocb_iter_write(real.file, &aio_req->iocb, iter);
+		ovl_aio_put(aio_req);
+		if (ret != -EIOCBQUEUED)
+			ovl_aio_cleanup_handler(aio_req);
+	}
+out:
+	revert_creds(old_cred);
+out_fdput:
+	fdput(real);
+
+out_unlock:
+	inode_unlock(inode);
+
+	return ret;
+}
+
+static ssize_t ovl_splice_read(struct file *in, loff_t *ppos,
+			       struct pipe_inode_info *pipe, size_t len,
+			       unsigned int flags)
+{
+	const struct cred *old_cred;
+	struct fd real;
+	ssize_t ret;
+
+	ret = ovl_real_fdget(in, &real);
+	if (ret)
+		return ret;
+
+	old_cred = ovl_override_creds(file_inode(in)->i_sb);
+	ret = vfs_splice_read(real.file, ppos, pipe, len, flags);
+	revert_creds(old_cred);
+	ovl_file_accessed(in);
+
+	fdput(real);
+	return ret;
+}
+
+/*
+ * Calling iter_file_splice_write() directly from overlay's f_op may deadlock
+ * due to lock order inversion between pipe->mutex in iter_file_splice_write()
+ * and file_start_write(real.file) in ovl_write_iter().
+ *
+ * So do everything ovl_write_iter() does and call iter_file_splice_write() on
+ * the real file.
+ */
+static ssize_t ovl_splice_write(struct pipe_inode_info *pipe, struct file *out,
+				loff_t *ppos, size_t len, unsigned int flags)
+{
+	struct fd real;
+	const struct cred *old_cred;
+	struct inode *inode = file_inode(out);
+	ssize_t ret;
+
+	inode_lock(inode);
+	/* Update mode */
+	ovl_copyattr(inode);
+	ret = file_remove_privs(out);
+	if (ret)
+		goto out_unlock;
+
+	ret = ovl_real_fdget(out, &real);
+	if (ret)
+		goto out_unlock;
+
+	old_cred = ovl_override_creds(inode->i_sb);
+	file_start_write(real.file);
+
+	ret = iter_file_splice_write(pipe, real.file, ppos, len, flags);
+
+	file_end_write(real.file);
+	/* Update size */
+	ovl_copyattr(inode);
+	revert_creds(old_cred);
+	fdput(real);
+
+out_unlock:
+	inode_unlock(inode);
+
+	return ret;
+}
+
+static int ovl_fsync(struct file *file, loff_t start, loff_t end, int datasync)
+{
+	struct fd real;
+	const struct cred *old_cred;
+	int ret;
+
+	ret = ovl_sync_status(OVL_FS(file_inode(file)->i_sb));
+	if (ret <= 0)
+		return ret;
+
+	ret = ovl_real_fdget_meta(file, &real, !datasync);
+	if (ret)
+		return ret;
+
+	/* Don't sync lower file for fear of receiving EROFS error */
+	if (file_inode(real.file) == ovl_inode_upper(file_inode(file))) {
+		old_cred = ovl_override_creds(file_inode(file)->i_sb);
+		ret = vfs_fsync_range(real.file, start, end, datasync);
+		revert_creds(old_cred);
+	}
+
+	fdput(real);
+
+	return ret;
+}
+
+static int ovl_mmap(struct file *file, struct vm_area_struct *vma)
+{
+	struct file *realfile = file->private_data;
+	const struct cred *old_cred;
+	int ret;
+
+	if (!realfile->f_op->mmap)
+		return -ENODEV;
+
+	if (WARN_ON(file != vma->vm_file))
+		return -EIO;
+
+	vma_set_file(vma, realfile);
+
+	old_cred = ovl_override_creds(file_inode(file)->i_sb);
+	ret = call_mmap(vma->vm_file, vma);
+	revert_creds(old_cred);
+	ovl_file_accessed(file);
+
+	return ret;
+}
+
+static long ovl_fallocate(struct file *file, int mode, loff_t offset, loff_t len)
+{
+	struct inode *inode = file_inode(file);
+	struct fd real;
+	const struct cred *old_cred;
+	int ret;
+
+	inode_lock(inode);
+	/* Update mode */
+	ovl_copyattr(inode);
+	ret = file_remove_privs(file);
+	if (ret)
+		goto out_unlock;
+
+	ret = ovl_real_fdget(file, &real);
+	if (ret)
+		goto out_unlock;
+
+	old_cred = ovl_override_creds(file_inode(file)->i_sb);
+	ret = vfs_fallocate(real.file, mode, offset, len);
+	revert_creds(old_cred);
+
+	/* Update size */
+	ovl_copyattr(inode);
+
+	fdput(real);
+
+out_unlock:
+	inode_unlock(inode);
+
+	return ret;
+}
+
+static int ovl_fadvise(struct file *file, loff_t offset, loff_t len, int advice)
+{
+	struct fd real;
+	const struct cred *old_cred;
+	int ret;
+
+	ret = ovl_real_fdget(file, &real);
+	if (ret)
+		return ret;
+
+	old_cred = ovl_override_creds(file_inode(file)->i_sb);
+	ret = vfs_fadvise(real.file, offset, len, advice);
+	revert_creds(old_cred);
+
+	fdput(real);
+
+	return ret;
+}
+
+enum ovl_copyop {
+	OVL_COPY,
+	OVL_CLONE,
+	OVL_DEDUPE,
+};
+
+static loff_t ovl_copyfile(struct file *file_in, loff_t pos_in,
+			    struct file *file_out, loff_t pos_out,
+			    loff_t len, unsigned int flags, enum ovl_copyop op)
+{
+	struct inode *inode_out = file_inode(file_out);
+	struct fd real_in, real_out;
+	const struct cred *old_cred;
+	loff_t ret;
+
+	inode_lock(inode_out);
+	if (op != OVL_DEDUPE) {
+		/* Update mode */
+		ovl_copyattr(inode_out);
+		ret = file_remove_privs(file_out);
+		if (ret)
+			goto out_unlock;
+	}
+
+	ret = ovl_real_fdget(file_out, &real_out);
+	if (ret)
+		goto out_unlock;
+
+	ret = ovl_real_fdget(file_in, &real_in);
+	if (ret) {
+		fdput(real_out);
+		goto out_unlock;
+	}
+
+	old_cred = ovl_override_creds(file_inode(file_out)->i_sb);
+	switch (op) {
+	case OVL_COPY:
+		ret = vfs_copy_file_range(real_in.file, pos_in,
+					  real_out.file, pos_out, len, flags);
+		break;
+
+	case OVL_CLONE:
+		ret = vfs_clone_file_range(real_in.file, pos_in,
+					   real_out.file, pos_out, len, flags);
+		break;
+
+	case OVL_DEDUPE:
+		ret = vfs_dedupe_file_range_one(real_in.file, pos_in,
+						real_out.file, pos_out, len,
+						flags);
+		break;
+	}
+	revert_creds(old_cred);
+
+	/* Update size */
+	ovl_copyattr(inode_out);
+
+	fdput(real_in);
+	fdput(real_out);
+
+out_unlock:
+	inode_unlock(inode_out);
+
+	return ret;
+}
+
+static ssize_t ovl_copy_file_range(struct file *file_in, loff_t pos_in,
+				   struct file *file_out, loff_t pos_out,
+				   size_t len, unsigned int flags)
+{
+	return ovl_copyfile(file_in, pos_in, file_out, pos_out, len, flags,
+			    OVL_COPY);
+}
+
+static loff_t ovl_remap_file_range(struct file *file_in, loff_t pos_in,
+				   struct file *file_out, loff_t pos_out,
+				   loff_t len, unsigned int remap_flags)
+{
+	enum ovl_copyop op;
+
+	if (remap_flags & ~(REMAP_FILE_DEDUP | REMAP_FILE_ADVISORY))
+		return -EINVAL;
+
+	if (remap_flags & REMAP_FILE_DEDUP)
+		op = OVL_DEDUPE;
+	else
+		op = OVL_CLONE;
+
+	/*
+	 * Don't copy up because of a dedupe request, this wouldn't make sense
+	 * most of the time (data would be duplicated instead of deduplicated).
+	 */
+	if (op == OVL_DEDUPE &&
+	    (!ovl_inode_upper(file_inode(file_in)) ||
+	     !ovl_inode_upper(file_inode(file_out))))
+		return -EPERM;
+
+	return ovl_copyfile(file_in, pos_in, file_out, pos_out, len,
+			    remap_flags, op);
+}
+
+static int ovl_flush(struct file *file, fl_owner_t id)
+{
+	struct fd real;
+	const struct cred *old_cred;
+	int err;
+
+	err = ovl_real_fdget(file, &real);
+	if (err)
+		return err;
+
+	if (real.file->f_op->flush) {
+		old_cred = ovl_override_creds(file_inode(file)->i_sb);
+		err = real.file->f_op->flush(real.file, id);
+		revert_creds(old_cred);
+	}
+	fdput(real);
+
+	return err;
+}
+
+const struct file_operations ovl_file_operations = {
+	.open		= ovl_open,
+	.release	= ovl_release,
+	.llseek		= ovl_llseek,
+	.read_iter	= ovl_read_iter,
+	.write_iter	= ovl_write_iter,
+	.fsync		= ovl_fsync,
+	.mmap		= ovl_mmap,
+	.fallocate	= ovl_fallocate,
+	.fadvise	= ovl_fadvise,
+	.flush		= ovl_flush,
+	.splice_read    = ovl_splice_read,
+	.splice_write   = ovl_splice_write,
+
+	.copy_file_range	= ovl_copy_file_range,
+	.remap_file_range	= ovl_remap_file_range,
+};
+
+int __init ovl_aio_request_cache_init(void)
+{
+	ovl_aio_request_cachep = kmem_cache_create("ovl_aio_req",
+						   sizeof(struct ovl_aio_req),
+						   0, SLAB_HWCACHE_ALIGN, NULL);
+	if (!ovl_aio_request_cachep)
+		return -ENOMEM;
+
+	return 0;
+}
+
+void ovl_aio_request_cache_destroy(void)
+{
+	kmem_cache_destroy(ovl_aio_request_cachep);
+}