Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 53a2731f authored by Michael Halcrow's avatar Michael Halcrow Committed by Linus Torvalds
Browse files

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: default avatarMichael Halcrow <mhalcrow@us.ibm.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 4acb3e2f

fs/ecryptfs/file.c

+1 −58
Original line number Diff line number Diff line
@@ -32,63 +32,6 @@ 
#include <linux/fs_stack.h>

#include "ecryptfs_kernel.h"



/**

 * ecryptfs_llseek

 * @file: File we are seeking in

 * @offset: The offset to seek to

 * @origin: 2 - offset from i_size; 1 - offset from f_pos

 *

 * Returns the position we have seeked to, or negative on error

 */

static loff_t ecryptfs_llseek(struct file *file, loff_t offset, int origin)

{

	loff_t rv;

	loff_t new_end_pos;

	int rc;

	int expanding_file = 0;

	struct inode *inode = file->f_mapping->host;



	/* If our offset is past the end of our file, we're going to

	 * need to grow it so we have a valid length of 0's */

	new_end_pos = offset;

	switch (origin) {

	case 2:

		new_end_pos += i_size_read(inode);

		expanding_file = 1;

		break;

	case 1:

		new_end_pos += file->f_pos;

		if (new_end_pos > i_size_read(inode)) {

			ecryptfs_printk(KERN_DEBUG, "new_end_pos(=[0x%.16x]) "

					"> i_size_read(inode)(=[0x%.16x])\n",

					new_end_pos, i_size_read(inode));

			expanding_file = 1;

		}

		break;

	default:

		if (new_end_pos > i_size_read(inode)) {

			ecryptfs_printk(KERN_DEBUG, "new_end_pos(=[0x%.16x]) "

					"> i_size_read(inode)(=[0x%.16x])\n",

					new_end_pos, i_size_read(inode));

			expanding_file = 1;

		}

	}

	ecryptfs_printk(KERN_DEBUG, "new_end_pos = [0x%.16x]\n", new_end_pos);

	if (expanding_file) {

		rc = ecryptfs_truncate(file->f_path.dentry, new_end_pos);

		if (rc) {

			rv = rc;

			ecryptfs_printk(KERN_ERR, "Error on attempt to "

					"truncate to (higher) offset [0x%.16x];"

					" rc = [%d]\n", new_end_pos, rc);

			goto out;

		}

	}

	rv = generic_file_llseek(file, offset, origin);

out:

	return rv;

}



/**

 * ecryptfs_read_update_atime

 *
@@ -425,7 +368,7 @@ const struct file_operations ecryptfs_dir_fops = { 
};



const struct file_operations ecryptfs_main_fops = {

	.llseek = ecryptfs_llseek,

	.llseek = generic_file_llseek,

	.read = do_sync_read,

	.aio_read = ecryptfs_read_update_atime,

	.write = do_sync_write,

fs/ecryptfs/mmap.c

+35 −3
Original line number Diff line number Diff line
@@ -376,9 +376,31 @@ static int fill_zeros_to_end_of_page(struct page *page, unsigned int to) 
	return 0;

}



/**

 * eCryptfs does not currently support holes. When writing after a

 * seek past the end of the file, eCryptfs fills in 0's through to the

 * current location. The code to fill in the 0's to all the

 * intermediate pages calls ecryptfs_prepare_write_no_truncate().

 */

static int

ecryptfs_prepare_write_no_truncate(struct file *file, struct page *page,

				   unsigned from, unsigned to)

{

	int rc = 0;



	if (from == 0 && to == PAGE_CACHE_SIZE)

		goto out;	/* If we are writing a full page, it will be

				   up to date. */

	if (!PageUptodate(page))

		rc = ecryptfs_do_readpage(file, page, page->index);

out:

	return rc;

}



static int ecryptfs_prepare_write(struct file *file, struct page *page,

				  unsigned from, unsigned to)

{

	loff_t pos;

	int rc = 0;



	if (from == 0 && to == PAGE_CACHE_SIZE)
@@ -386,6 +408,16 @@ static int ecryptfs_prepare_write(struct file *file, struct page *page, 
				   up to date. */

	if (!PageUptodate(page))

		rc = ecryptfs_do_readpage(file, page, page->index);

	pos = ((loff_t)page->index << PAGE_CACHE_SHIFT) + to;

	if (pos > i_size_read(page->mapping->host)) {

		rc = ecryptfs_truncate(file->f_path.dentry, pos);

		if (rc) {

			printk(KERN_ERR "Error on attempt to "

			       "truncate to (higher) offset [%lld];"

			       " rc = [%d]\n", pos, rc);

			goto out;

		}

	}

out:

	return rc;

}
@@ -744,10 +776,10 @@ int write_zeros(struct file *file, pgoff_t index, int start, int num_zeros) 
		rc = PTR_ERR(tmp_page);

		goto out;

	}

	rc = ecryptfs_prepare_write(file, tmp_page, start, start + num_zeros);

	if (rc) {

	if ((rc = ecryptfs_prepare_write_no_truncate(file, tmp_page, start,

						     (start + num_zeros)))) {

		ecryptfs_printk(KERN_ERR, "Error preparing to write zero's "

				"to remainder of page at index [0x%.16x]\n",

				"to page at index [0x%.16x]\n",

				index);

		page_cache_release(tmp_page);

		goto out;