1 files changed, 482 insertions, 0 deletions

diff --git a/fs/configfs/file.c b/fs/configfs/file.c
new file mode 100644
index 000000000..0ad321506
--- /dev/null
+++ b/fs/configfs/file.c
@@ -0,0 +1,482 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * file.c - operations for regular (text) files.
+ *
+ * Based on sysfs:
+ * 	sysfs is Copyright (C) 2001, 2002, 2003 Patrick Mochel
+ *
+ * configfs Copyright (C) 2005 Oracle.  All rights reserved.
+ */
+
+#include <linux/fs.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/mutex.h>
+#include <linux/vmalloc.h>
+#include <linux/uaccess.h>
+#include <linux/uio.h>
+#include <linux/configfs.h>
+#include "configfs_internal.h"
+
+/*
+ * A simple attribute can only be 4096 characters.  Why 4k?  Because the
+ * original code limited it to PAGE_SIZE.  That's a bad idea, though,
+ * because an attribute of 16k on ia64 won't work on x86.  So we limit to
+ * 4k, our minimum common page size.
+ */
+#define SIMPLE_ATTR_SIZE 4096
+
+struct configfs_buffer {
+	size_t			count;
+	loff_t			pos;
+	char			* page;
+	struct configfs_item_operations	* ops;
+	struct mutex		mutex;
+	int			needs_read_fill;
+	bool			read_in_progress;
+	bool			write_in_progress;
+	char			*bin_buffer;
+	int			bin_buffer_size;
+	int			cb_max_size;
+	struct config_item	*item;
+	struct module		*owner;
+	union {
+		struct configfs_attribute	*attr;
+		struct configfs_bin_attribute	*bin_attr;
+	};
+};
+
+static inline struct configfs_fragment *to_frag(struct file *file)
+{
+	struct configfs_dirent *sd = file->f_path.dentry->d_fsdata;
+
+	return sd->s_frag;
+}
+
+static int fill_read_buffer(struct file *file, struct configfs_buffer *buffer)
+{
+	struct configfs_fragment *frag = to_frag(file);
+	ssize_t count = -ENOENT;
+
+	if (!buffer->page)
+		buffer->page = (char *) get_zeroed_page(GFP_KERNEL);
+	if (!buffer->page)
+		return -ENOMEM;
+
+	down_read(&frag->frag_sem);
+	if (!frag->frag_dead)
+		count = buffer->attr->show(buffer->item, buffer->page);
+	up_read(&frag->frag_sem);
+
+	if (count < 0)
+		return count;
+	if (WARN_ON_ONCE(count > (ssize_t)SIMPLE_ATTR_SIZE))
+		return -EIO;
+	buffer->needs_read_fill = 0;
+	buffer->count = count;
+	return 0;
+}
+
+static ssize_t configfs_read_iter(struct kiocb *iocb, struct iov_iter *to)
+{
+	struct file *file = iocb->ki_filp;
+	struct configfs_buffer *buffer = file->private_data;
+	ssize_t retval = 0;
+
+	mutex_lock(&buffer->mutex);
+	if (buffer->needs_read_fill) {
+		retval = fill_read_buffer(file, buffer);
+		if (retval)
+			goto out;
+	}
+	pr_debug("%s: count = %zd, pos = %lld, buf = %s\n",
+		 __func__, iov_iter_count(to), iocb->ki_pos, buffer->page);
+	if (iocb->ki_pos >= buffer->count)
+		goto out;
+	retval = copy_to_iter(buffer->page + iocb->ki_pos,
+			      buffer->count - iocb->ki_pos, to);
+	iocb->ki_pos += retval;
+	if (retval == 0)
+		retval = -EFAULT;
+out:
+	mutex_unlock(&buffer->mutex);
+	return retval;
+}
+
+static ssize_t configfs_bin_read_iter(struct kiocb *iocb, struct iov_iter *to)
+{
+	struct file *file = iocb->ki_filp;
+	struct configfs_fragment *frag = to_frag(file);
+	struct configfs_buffer *buffer = file->private_data;
+	ssize_t retval = 0;
+	ssize_t len;
+
+	mutex_lock(&buffer->mutex);
+
+	/* we don't support switching read/write modes */
+	if (buffer->write_in_progress) {
+		retval = -ETXTBSY;
+		goto out;
+	}
+	buffer->read_in_progress = true;
+
+	if (buffer->needs_read_fill) {
+		/* perform first read with buf == NULL to get extent */
+		down_read(&frag->frag_sem);
+		if (!frag->frag_dead)
+			len = buffer->bin_attr->read(buffer->item, NULL, 0);
+		else
+			len = -ENOENT;
+		up_read(&frag->frag_sem);
+		if (len <= 0) {
+			retval = len;
+			goto out;
+		}
+
+		/* do not exceed the maximum value */
+		if (buffer->cb_max_size && len > buffer->cb_max_size) {
+			retval = -EFBIG;
+			goto out;
+		}
+
+		buffer->bin_buffer = vmalloc(len);
+		if (buffer->bin_buffer == NULL) {
+			retval = -ENOMEM;
+			goto out;
+		}
+		buffer->bin_buffer_size = len;
+
+		/* perform second read to fill buffer */
+		down_read(&frag->frag_sem);
+		if (!frag->frag_dead)
+			len = buffer->bin_attr->read(buffer->item,
+						     buffer->bin_buffer, len);
+		else
+			len = -ENOENT;
+		up_read(&frag->frag_sem);
+		if (len < 0) {
+			retval = len;
+			vfree(buffer->bin_buffer);
+			buffer->bin_buffer_size = 0;
+			buffer->bin_buffer = NULL;
+			goto out;
+		}
+
+		buffer->needs_read_fill = 0;
+	}
+
+	if (iocb->ki_pos >= buffer->bin_buffer_size)
+		goto out;
+	retval = copy_to_iter(buffer->bin_buffer + iocb->ki_pos,
+			      buffer->bin_buffer_size - iocb->ki_pos, to);
+	iocb->ki_pos += retval;
+	if (retval == 0)
+		retval = -EFAULT;
+out:
+	mutex_unlock(&buffer->mutex);
+	return retval;
+}
+
+/* Fill @buffer with data coming from @from. */
+static int fill_write_buffer(struct configfs_buffer *buffer,
+			     struct iov_iter *from)
+{
+	int copied;
+
+	if (!buffer->page)
+		buffer->page = (char *)__get_free_pages(GFP_KERNEL, 0);
+	if (!buffer->page)
+		return -ENOMEM;
+
+	copied = copy_from_iter(buffer->page, SIMPLE_ATTR_SIZE - 1, from);
+	buffer->needs_read_fill = 1;
+	/* if buf is assumed to contain a string, terminate it by \0,
+	 * so e.g. sscanf() can scan the string easily */
+	buffer->page[copied] = 0;
+	return copied ? : -EFAULT;
+}
+
+static int
+flush_write_buffer(struct file *file, struct configfs_buffer *buffer, size_t count)
+{
+	struct configfs_fragment *frag = to_frag(file);
+	int res = -ENOENT;
+
+	down_read(&frag->frag_sem);
+	if (!frag->frag_dead)
+		res = buffer->attr->store(buffer->item, buffer->page, count);
+	up_read(&frag->frag_sem);
+	return res;
+}
+
+
+/*
+ * There is no easy way for us to know if userspace is only doing a partial
+ * write, so we don't support them. We expect the entire buffer to come on the
+ * first write.
+ * Hint: if you're writing a value, first read the file, modify only the value
+ * you're changing, then write entire buffer back.
+ */
+static ssize_t configfs_write_iter(struct kiocb *iocb, struct iov_iter *from)
+{
+	struct file *file = iocb->ki_filp;
+	struct configfs_buffer *buffer = file->private_data;
+	int len;
+
+	mutex_lock(&buffer->mutex);
+	len = fill_write_buffer(buffer, from);
+	if (len > 0)
+		len = flush_write_buffer(file, buffer, len);
+	if (len > 0)
+		iocb->ki_pos += len;
+	mutex_unlock(&buffer->mutex);
+	return len;
+}
+
+static ssize_t configfs_bin_write_iter(struct kiocb *iocb,
+				       struct iov_iter *from)
+{
+	struct file *file = iocb->ki_filp;
+	struct configfs_buffer *buffer = file->private_data;
+	void *tbuf = NULL;
+	size_t end_offset;
+	ssize_t len;
+
+	mutex_lock(&buffer->mutex);
+
+	/* we don't support switching read/write modes */
+	if (buffer->read_in_progress) {
+		len = -ETXTBSY;
+		goto out;
+	}
+	buffer->write_in_progress = true;
+
+	/* buffer grows? */
+	end_offset = iocb->ki_pos + iov_iter_count(from);
+	if (end_offset > buffer->bin_buffer_size) {
+		if (buffer->cb_max_size && end_offset > buffer->cb_max_size) {
+			len = -EFBIG;
+			goto out;
+		}
+
+		tbuf = vmalloc(end_offset);
+		if (tbuf == NULL) {
+			len = -ENOMEM;
+			goto out;
+		}
+
+		/* copy old contents */
+		if (buffer->bin_buffer) {
+			memcpy(tbuf, buffer->bin_buffer,
+				buffer->bin_buffer_size);
+			vfree(buffer->bin_buffer);
+		}
+
+		/* clear the new area */
+		memset(tbuf + buffer->bin_buffer_size, 0,
+			end_offset - buffer->bin_buffer_size);
+		buffer->bin_buffer = tbuf;
+		buffer->bin_buffer_size = end_offset;
+	}
+
+	len = copy_from_iter(buffer->bin_buffer + iocb->ki_pos,
+			     buffer->bin_buffer_size - iocb->ki_pos, from);
+	iocb->ki_pos += len;
+out:
+	mutex_unlock(&buffer->mutex);
+	return len ? : -EFAULT;
+}
+
+static int __configfs_open_file(struct inode *inode, struct file *file, int type)
+{
+	struct dentry *dentry = file->f_path.dentry;
+	struct configfs_fragment *frag = to_frag(file);
+	struct configfs_attribute *attr;
+	struct configfs_buffer *buffer;
+	int error;
+
+	error = -ENOMEM;
+	buffer = kzalloc(sizeof(struct configfs_buffer), GFP_KERNEL);
+	if (!buffer)
+		goto out;
+
+	error = -ENOENT;
+	down_read(&frag->frag_sem);
+	if (unlikely(frag->frag_dead))
+		goto out_free_buffer;
+
+	error = -EINVAL;
+	buffer->item = to_item(dentry->d_parent);
+	if (!buffer->item)
+		goto out_free_buffer;
+
+	attr = to_attr(dentry);
+	if (!attr)
+		goto out_free_buffer;
+
+	if (type & CONFIGFS_ITEM_BIN_ATTR) {
+		buffer->bin_attr = to_bin_attr(dentry);
+		buffer->cb_max_size = buffer->bin_attr->cb_max_size;
+	} else {
+		buffer->attr = attr;
+	}
+
+	buffer->owner = attr->ca_owner;
+	/* Grab the module reference for this attribute if we have one */
+	error = -ENODEV;
+	if (!try_module_get(buffer->owner))
+		goto out_free_buffer;
+
+	error = -EACCES;
+	if (!buffer->item->ci_type)
+		goto out_put_module;
+
+	buffer->ops = buffer->item->ci_type->ct_item_ops;
+
+	/* File needs write support.
+	 * The inode's perms must say it's ok,
+	 * and we must have a store method.
+	 */
+	if (file->f_mode & FMODE_WRITE) {
+		if (!(inode->i_mode & S_IWUGO))
+			goto out_put_module;
+		if ((type & CONFIGFS_ITEM_ATTR) && !attr->store)
+			goto out_put_module;
+		if ((type & CONFIGFS_ITEM_BIN_ATTR) && !buffer->bin_attr->write)
+			goto out_put_module;
+	}
+
+	/* File needs read support.
+	 * The inode's perms must say it's ok, and we there
+	 * must be a show method for it.
+	 */
+	if (file->f_mode & FMODE_READ) {
+		if (!(inode->i_mode & S_IRUGO))
+			goto out_put_module;
+		if ((type & CONFIGFS_ITEM_ATTR) && !attr->show)
+			goto out_put_module;
+		if ((type & CONFIGFS_ITEM_BIN_ATTR) && !buffer->bin_attr->read)
+			goto out_put_module;
+	}
+
+	mutex_init(&buffer->mutex);
+	buffer->needs_read_fill = 1;
+	buffer->read_in_progress = false;
+	buffer->write_in_progress = false;
+	file->private_data = buffer;
+	up_read(&frag->frag_sem);
+	return 0;
+
+out_put_module:
+	module_put(buffer->owner);
+out_free_buffer:
+	up_read(&frag->frag_sem);
+	kfree(buffer);
+out:
+	return error;
+}
+
+static int configfs_release(struct inode *inode, struct file *filp)
+{
+	struct configfs_buffer *buffer = filp->private_data;
+
+	module_put(buffer->owner);
+	if (buffer->page)
+		free_page((unsigned long)buffer->page);
+	mutex_destroy(&buffer->mutex);
+	kfree(buffer);
+	return 0;
+}
+
+static int configfs_open_file(struct inode *inode, struct file *filp)
+{
+	return __configfs_open_file(inode, filp, CONFIGFS_ITEM_ATTR);
+}
+
+static int configfs_open_bin_file(struct inode *inode, struct file *filp)
+{
+	return __configfs_open_file(inode, filp, CONFIGFS_ITEM_BIN_ATTR);
+}
+
+static int configfs_release_bin_file(struct inode *inode, struct file *file)
+{
+	struct configfs_buffer *buffer = file->private_data;
+
+	if (buffer->write_in_progress) {
+		struct configfs_fragment *frag = to_frag(file);
+
+		down_read(&frag->frag_sem);
+		if (!frag->frag_dead) {
+			/* result of ->release() is ignored */
+			buffer->bin_attr->write(buffer->item,
+					buffer->bin_buffer,
+					buffer->bin_buffer_size);
+		}
+		up_read(&frag->frag_sem);
+	}
+
+	vfree(buffer->bin_buffer);
+
+	configfs_release(inode, file);
+	return 0;
+}
+
+
+const struct file_operations configfs_file_operations = {
+	.read_iter	= configfs_read_iter,
+	.write_iter	= configfs_write_iter,
+	.llseek		= generic_file_llseek,
+	.open		= configfs_open_file,
+	.release	= configfs_release,
+};
+
+const struct file_operations configfs_bin_file_operations = {
+	.read_iter	= configfs_bin_read_iter,
+	.write_iter	= configfs_bin_write_iter,
+	.llseek		= NULL,		/* bin file is not seekable */
+	.open		= configfs_open_bin_file,
+	.release	= configfs_release_bin_file,
+};
+
+/**
+ *	configfs_create_file - create an attribute file for an item.
+ *	@item:	item we're creating for.
+ *	@attr:	atrribute descriptor.
+ */
+
+int configfs_create_file(struct config_item * item, const struct configfs_attribute * attr)
+{
+	struct dentry *dir = item->ci_dentry;
+	struct configfs_dirent *parent_sd = dir->d_fsdata;
+	umode_t mode = (attr->ca_mode & S_IALLUGO) | S_IFREG;
+	int error = 0;
+
+	inode_lock_nested(d_inode(dir), I_MUTEX_NORMAL);
+	error = configfs_make_dirent(parent_sd, NULL, (void *) attr, mode,
+				     CONFIGFS_ITEM_ATTR, parent_sd->s_frag);
+	inode_unlock(d_inode(dir));
+
+	return error;
+}
+
+/**
+ *	configfs_create_bin_file - create a binary attribute file for an item.
+ *	@item:	item we're creating for.
+ *	@bin_attr: atrribute descriptor.
+ */
+
+int configfs_create_bin_file(struct config_item *item,
+		const struct configfs_bin_attribute *bin_attr)
+{
+	struct dentry *dir = item->ci_dentry;
+	struct configfs_dirent *parent_sd = dir->d_fsdata;
+	umode_t mode = (bin_attr->cb_attr.ca_mode & S_IALLUGO) | S_IFREG;
+	int error = 0;
+
+	inode_lock_nested(dir->d_inode, I_MUTEX_NORMAL);
+	error = configfs_make_dirent(parent_sd, NULL, (void *) bin_attr, mode,
+				     CONFIGFS_ITEM_BIN_ATTR, parent_sd->s_frag);
+	inode_unlock(dir->d_inode);
+
+	return error;
+}