eCryptfs: delay writing 0's after llseek until write
Delay writing 0's out in eCryptfs after a seek past the end of the file until data is actually written. http://www.opengroup.org/onlinepubs/009695399/functions/lseek.html ``The lseek() function shall not, by itself, extend the size of a file.'' Without this fix, applications that lseek() past the end of the file without writing will experience unexpected behavior. Signed-off-by: Michael Halcrow <mhalcrow@us.ibm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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@ -32,63 +32,6 @@
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#include <linux/fs_stack.h>
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#include "ecryptfs_kernel.h"
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/**
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* ecryptfs_llseek
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* @file: File we are seeking in
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* @offset: The offset to seek to
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* @origin: 2 - offset from i_size; 1 - offset from f_pos
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*
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* Returns the position we have seeked to, or negative on error
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*/
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static loff_t ecryptfs_llseek(struct file *file, loff_t offset, int origin)
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{
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loff_t rv;
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loff_t new_end_pos;
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int rc;
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int expanding_file = 0;
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struct inode *inode = file->f_mapping->host;
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/* If our offset is past the end of our file, we're going to
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* need to grow it so we have a valid length of 0's */
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new_end_pos = offset;
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switch (origin) {
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case 2:
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new_end_pos += i_size_read(inode);
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expanding_file = 1;
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break;
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case 1:
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new_end_pos += file->f_pos;
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if (new_end_pos > i_size_read(inode)) {
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ecryptfs_printk(KERN_DEBUG, "new_end_pos(=[0x%.16x]) "
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"> i_size_read(inode)(=[0x%.16x])\n",
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new_end_pos, i_size_read(inode));
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expanding_file = 1;
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}
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break;
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default:
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if (new_end_pos > i_size_read(inode)) {
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ecryptfs_printk(KERN_DEBUG, "new_end_pos(=[0x%.16x]) "
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"> i_size_read(inode)(=[0x%.16x])\n",
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new_end_pos, i_size_read(inode));
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expanding_file = 1;
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}
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}
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ecryptfs_printk(KERN_DEBUG, "new_end_pos = [0x%.16x]\n", new_end_pos);
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if (expanding_file) {
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rc = ecryptfs_truncate(file->f_path.dentry, new_end_pos);
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if (rc) {
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rv = rc;
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ecryptfs_printk(KERN_ERR, "Error on attempt to "
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"truncate to (higher) offset [0x%.16x];"
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" rc = [%d]\n", new_end_pos, rc);
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goto out;
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}
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}
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rv = generic_file_llseek(file, offset, origin);
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out:
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return rv;
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}
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/**
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* ecryptfs_read_update_atime
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*
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@ -425,7 +368,7 @@ const struct file_operations ecryptfs_dir_fops = {
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};
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const struct file_operations ecryptfs_main_fops = {
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.llseek = ecryptfs_llseek,
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.llseek = generic_file_llseek,
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.read = do_sync_read,
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.aio_read = ecryptfs_read_update_atime,
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.write = do_sync_write,
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@ -376,8 +376,15 @@ out:
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return 0;
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}
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static int ecryptfs_prepare_write(struct file *file, struct page *page,
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unsigned from, unsigned to)
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/**
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* eCryptfs does not currently support holes. When writing after a
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* seek past the end of the file, eCryptfs fills in 0's through to the
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* current location. The code to fill in the 0's to all the
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* intermediate pages calls ecryptfs_prepare_write_no_truncate().
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*/
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static int
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ecryptfs_prepare_write_no_truncate(struct file *file, struct page *page,
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unsigned from, unsigned to)
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{
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int rc = 0;
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@ -390,6 +397,31 @@ out:
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return rc;
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}
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static int ecryptfs_prepare_write(struct file *file, struct page *page,
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unsigned from, unsigned to)
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{
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loff_t pos;
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int rc = 0;
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if (from == 0 && to == PAGE_CACHE_SIZE)
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goto out; /* If we are writing a full page, it will be
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up to date. */
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if (!PageUptodate(page))
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rc = ecryptfs_do_readpage(file, page, page->index);
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pos = ((loff_t)page->index << PAGE_CACHE_SHIFT) + to;
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if (pos > i_size_read(page->mapping->host)) {
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rc = ecryptfs_truncate(file->f_path.dentry, pos);
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if (rc) {
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printk(KERN_ERR "Error on attempt to "
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"truncate to (higher) offset [%lld];"
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" rc = [%d]\n", pos, rc);
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goto out;
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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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int ecryptfs_writepage_and_release_lower_page(struct page *lower_page,
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struct inode *lower_inode,
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struct writeback_control *wbc)
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@ -744,10 +776,10 @@ int write_zeros(struct file *file, pgoff_t index, int start, int num_zeros)
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rc = PTR_ERR(tmp_page);
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goto out;
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}
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rc = ecryptfs_prepare_write(file, tmp_page, start, start + num_zeros);
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if (rc) {
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if ((rc = ecryptfs_prepare_write_no_truncate(file, tmp_page, start,
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(start + num_zeros)))) {
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ecryptfs_printk(KERN_ERR, "Error preparing to write zero's "
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"to remainder of page at index [0x%.16x]\n",
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"to page at index [0x%.16x]\n",
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index);
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page_cache_release(tmp_page);
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goto out;
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