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263 lines
7.9 KiB
263 lines
7.9 KiB
// SPDX-License-Identifier: GPL-2.0-or-later |
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/* |
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* eCryptfs: Linux filesystem encryption layer |
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* |
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* Copyright (C) 2007 International Business Machines Corp. |
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* Author(s): Michael A. Halcrow <[email protected]> |
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*/ |
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#include <linux/fs.h> |
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#include <linux/pagemap.h> |
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#include <linux/sched/signal.h> |
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#include "ecryptfs_kernel.h" |
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/** |
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* ecryptfs_write_lower |
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* @ecryptfs_inode: The eCryptfs inode |
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* @data: Data to write |
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* @offset: Byte offset in the lower file to which to write the data |
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* @size: Number of bytes from @data to write at @offset in the lower |
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* file |
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* |
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* Write data to the lower file. |
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* |
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* Returns bytes written on success; less than zero on error |
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*/ |
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int ecryptfs_write_lower(struct inode *ecryptfs_inode, char *data, |
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loff_t offset, size_t size) |
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{ |
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struct file *lower_file; |
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ssize_t rc; |
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lower_file = ecryptfs_inode_to_private(ecryptfs_inode)->lower_file; |
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if (!lower_file) |
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return -EIO; |
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rc = kernel_write(lower_file, data, size, &offset); |
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mark_inode_dirty_sync(ecryptfs_inode); |
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return rc; |
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} |
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/** |
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* ecryptfs_write_lower_page_segment |
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* @ecryptfs_inode: The eCryptfs inode |
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* @page_for_lower: The page containing the data to be written to the |
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* lower file |
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* @offset_in_page: The offset in the @page_for_lower from which to |
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* start writing the data |
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* @size: The amount of data from @page_for_lower to write to the |
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* lower file |
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* |
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* Determines the byte offset in the file for the given page and |
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* offset within the page, maps the page, and makes the call to write |
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* the contents of @page_for_lower to the lower inode. |
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* |
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* Returns zero on success; non-zero otherwise |
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*/ |
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int ecryptfs_write_lower_page_segment(struct inode *ecryptfs_inode, |
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struct page *page_for_lower, |
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size_t offset_in_page, size_t size) |
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{ |
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char *virt; |
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loff_t offset; |
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int rc; |
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offset = ((((loff_t)page_for_lower->index) << PAGE_SHIFT) |
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+ offset_in_page); |
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virt = kmap(page_for_lower); |
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rc = ecryptfs_write_lower(ecryptfs_inode, virt, offset, size); |
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if (rc > 0) |
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rc = 0; |
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kunmap(page_for_lower); |
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return rc; |
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} |
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/** |
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* ecryptfs_write |
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* @ecryptfs_inode: The eCryptfs file into which to write |
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* @data: Virtual address where data to write is located |
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* @offset: Offset in the eCryptfs file at which to begin writing the |
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* data from @data |
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* @size: The number of bytes to write from @data |
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* |
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* Write an arbitrary amount of data to an arbitrary location in the |
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* eCryptfs inode page cache. This is done on a page-by-page, and then |
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* by an extent-by-extent, basis; individual extents are encrypted and |
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* written to the lower page cache (via VFS writes). This function |
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* takes care of all the address translation to locations in the lower |
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* filesystem; it also handles truncate events, writing out zeros |
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* where necessary. |
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* |
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* Returns zero on success; non-zero otherwise |
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*/ |
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int ecryptfs_write(struct inode *ecryptfs_inode, char *data, loff_t offset, |
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size_t size) |
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{ |
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struct page *ecryptfs_page; |
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struct ecryptfs_crypt_stat *crypt_stat; |
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char *ecryptfs_page_virt; |
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loff_t ecryptfs_file_size = i_size_read(ecryptfs_inode); |
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loff_t data_offset = 0; |
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loff_t pos; |
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int rc = 0; |
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crypt_stat = &ecryptfs_inode_to_private(ecryptfs_inode)->crypt_stat; |
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/* |
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* if we are writing beyond current size, then start pos |
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* at the current size - we'll fill in zeros from there. |
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*/ |
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if (offset > ecryptfs_file_size) |
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pos = ecryptfs_file_size; |
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else |
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pos = offset; |
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while (pos < (offset + size)) { |
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pgoff_t ecryptfs_page_idx = (pos >> PAGE_SHIFT); |
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size_t start_offset_in_page = (pos & ~PAGE_MASK); |
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size_t num_bytes = (PAGE_SIZE - start_offset_in_page); |
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loff_t total_remaining_bytes = ((offset + size) - pos); |
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if (fatal_signal_pending(current)) { |
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rc = -EINTR; |
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break; |
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} |
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if (num_bytes > total_remaining_bytes) |
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num_bytes = total_remaining_bytes; |
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if (pos < offset) { |
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/* remaining zeros to write, up to destination offset */ |
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loff_t total_remaining_zeros = (offset - pos); |
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if (num_bytes > total_remaining_zeros) |
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num_bytes = total_remaining_zeros; |
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} |
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ecryptfs_page = ecryptfs_get_locked_page(ecryptfs_inode, |
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ecryptfs_page_idx); |
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if (IS_ERR(ecryptfs_page)) { |
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rc = PTR_ERR(ecryptfs_page); |
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printk(KERN_ERR "%s: Error getting page at " |
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"index [%ld] from eCryptfs inode " |
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"mapping; rc = [%d]\n", __func__, |
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ecryptfs_page_idx, rc); |
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goto out; |
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} |
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ecryptfs_page_virt = kmap_atomic(ecryptfs_page); |
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/* |
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* pos: where we're now writing, offset: where the request was |
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* If current pos is before request, we are filling zeros |
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* If we are at or beyond request, we are writing the *data* |
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* If we're in a fresh page beyond eof, zero it in either case |
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*/ |
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if (pos < offset || !start_offset_in_page) { |
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/* We are extending past the previous end of the file. |
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* Fill in zero values to the end of the page */ |
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memset(((char *)ecryptfs_page_virt |
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+ start_offset_in_page), 0, |
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PAGE_SIZE - start_offset_in_page); |
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} |
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/* pos >= offset, we are now writing the data request */ |
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if (pos >= offset) { |
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memcpy(((char *)ecryptfs_page_virt |
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+ start_offset_in_page), |
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(data + data_offset), num_bytes); |
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data_offset += num_bytes; |
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} |
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kunmap_atomic(ecryptfs_page_virt); |
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flush_dcache_page(ecryptfs_page); |
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SetPageUptodate(ecryptfs_page); |
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unlock_page(ecryptfs_page); |
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if (crypt_stat->flags & ECRYPTFS_ENCRYPTED) |
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rc = ecryptfs_encrypt_page(ecryptfs_page); |
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else |
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rc = ecryptfs_write_lower_page_segment(ecryptfs_inode, |
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ecryptfs_page, |
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start_offset_in_page, |
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data_offset); |
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put_page(ecryptfs_page); |
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if (rc) { |
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printk(KERN_ERR "%s: Error encrypting " |
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"page; rc = [%d]\n", __func__, rc); |
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goto out; |
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} |
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pos += num_bytes; |
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} |
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if (pos > ecryptfs_file_size) { |
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i_size_write(ecryptfs_inode, pos); |
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if (crypt_stat->flags & ECRYPTFS_ENCRYPTED) { |
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int rc2; |
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rc2 = ecryptfs_write_inode_size_to_metadata( |
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ecryptfs_inode); |
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if (rc2) { |
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printk(KERN_ERR "Problem with " |
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"ecryptfs_write_inode_size_to_metadata; " |
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"rc = [%d]\n", rc2); |
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if (!rc) |
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rc = rc2; |
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goto out; |
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} |
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} |
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} |
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out: |
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return rc; |
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} |
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/** |
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* ecryptfs_read_lower |
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* @data: The read data is stored here by this function |
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* @offset: Byte offset in the lower file from which to read the data |
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* @size: Number of bytes to read from @offset of the lower file and |
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* store into @data |
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* @ecryptfs_inode: The eCryptfs inode |
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* |
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* Read @size bytes of data at byte offset @offset from the lower |
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* inode into memory location @data. |
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* |
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* Returns bytes read on success; 0 on EOF; less than zero on error |
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*/ |
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int ecryptfs_read_lower(char *data, loff_t offset, size_t size, |
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struct inode *ecryptfs_inode) |
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{ |
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struct file *lower_file; |
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lower_file = ecryptfs_inode_to_private(ecryptfs_inode)->lower_file; |
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if (!lower_file) |
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return -EIO; |
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return kernel_read(lower_file, data, size, &offset); |
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} |
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/** |
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* ecryptfs_read_lower_page_segment |
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* @page_for_ecryptfs: The page into which data for eCryptfs will be |
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* written |
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* @page_index: Page index in @page_for_ecryptfs from which to start |
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* writing |
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* @offset_in_page: Offset in @page_for_ecryptfs from which to start |
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* writing |
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* @size: The number of bytes to write into @page_for_ecryptfs |
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* @ecryptfs_inode: The eCryptfs inode |
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* |
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* Determines the byte offset in the file for the given page and |
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* offset within the page, maps the page, and makes the call to read |
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* the contents of @page_for_ecryptfs from the lower inode. |
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* |
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* Returns zero on success; non-zero otherwise |
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*/ |
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int ecryptfs_read_lower_page_segment(struct page *page_for_ecryptfs, |
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pgoff_t page_index, |
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size_t offset_in_page, size_t size, |
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struct inode *ecryptfs_inode) |
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{ |
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char *virt; |
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loff_t offset; |
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int rc; |
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offset = ((((loff_t)page_index) << PAGE_SHIFT) + offset_in_page); |
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virt = kmap(page_for_ecryptfs); |
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rc = ecryptfs_read_lower(virt, offset, size, ecryptfs_inode); |
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if (rc > 0) |
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rc = 0; |
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kunmap(page_for_ecryptfs); |
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flush_dcache_page(page_for_ecryptfs); |
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return rc; |
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}
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