Commit 240e2df5 authored by Michael Halcrow's avatar Michael Halcrow Committed by Linus Torvalds
Browse files

eCryptfs: fix write zeros behavior 



This patch fixes the processes involved in wiping regions of the data during
truncate and write events, fixing a kernel hang in 2.6.22-rc4 while assuring
that zero values are written out to the appropriate locations during events in
which the i_size will change.

The range passed to ecryptfs_truncate() from ecryptfs_prepare_write() includes
the page that is the object of ecryptfs_prepare_write().  This leads to a
kernel hang as read_cache_page() is executed on the same page in the
ecryptfs_truncate() execution path.  This patch remedies this by limiting the
range passed to ecryptfs_truncate() so as to exclude the page that is the
object of ecryptfs_prepare_write(); it also adds code to
ecryptfs_prepare_write() to zero out the region of its own page when writing
past the i_size position.  This patch also modifies ecryptfs_truncate() so
that when a file is truncated to a smaller size, eCryptfs will zero out the
contents of the new last page from the new size through to the end of the last
page.

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 b75ae860

fs/ecryptfs/ecryptfs_kernel.h

+2 −0
Original line number Diff line number Diff line
@@ -580,5 +580,7 @@ void 
ecryptfs_write_header_metadata(char *virt,

			       struct ecryptfs_crypt_stat *crypt_stat,

			       size_t *written);

int ecryptfs_write_zeros(struct file *file, pgoff_t index, int start,

			 int num_zeros);



#endif /* #ifndef ECRYPTFS_KERNEL_H */

fs/ecryptfs/inode.c

+19 −0
Original line number Diff line number Diff line
@@ -800,6 +800,25 @@ int ecryptfs_truncate(struct dentry *dentry, loff_t new_length) 
			goto out_fput;

		}

	} else { /* new_length < i_size_read(inode) */

		pgoff_t index = 0;

		int end_pos_in_page = -1;



		if (new_length != 0) {

			index = ((new_length - 1) >> PAGE_CACHE_SHIFT);

			end_pos_in_page = ((new_length - 1) & ~PAGE_CACHE_MASK);

		}

		if (end_pos_in_page != (PAGE_CACHE_SIZE - 1)) {

			if ((rc = ecryptfs_write_zeros(&fake_ecryptfs_file,

						       index,

						       (end_pos_in_page + 1),

						       ((PAGE_CACHE_SIZE - 1)

							- end_pos_in_page)))) {

				printk(KERN_ERR "Error attempting to zero out "

				       "the remainder of the end page on "

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

				goto out_fput;

			}

		}

		vmtruncate(inode, new_length);

		rc = ecryptfs_write_inode_size_to_metadata(

			lower_file, lower_dentry->d_inode, inode, dentry,

fs/ecryptfs/mmap.c

+29 −24
Original line number Diff line number Diff line
@@ -56,9 +56,6 @@ static struct page *ecryptfs_get1page(struct file *file, int index) 
	return read_mapping_page(mapping, index, (void *)file);

}



static

int write_zeros(struct file *file, pgoff_t index, int start, int num_zeros);



/**

 * ecryptfs_fill_zeros

 * @file: The ecryptfs file
@@ -101,10 +98,13 @@ int ecryptfs_fill_zeros(struct file *file, loff_t new_length) 
	if (old_end_page_index == new_end_page_index) {

		/* Start and end are in the same page; we just need to

		 * set a portion of the existing page to zero's */

		rc = write_zeros(file, index, (old_end_pos_in_page + 1),

				 (new_end_pos_in_page - old_end_pos_in_page));

		rc = ecryptfs_write_zeros(file, index,

					  (old_end_pos_in_page + 1),

					  (new_end_pos_in_page

					   - old_end_pos_in_page));

		if (rc)

			ecryptfs_printk(KERN_ERR, "write_zeros(file=[%p], "

			ecryptfs_printk(KERN_ERR, "ecryptfs_write_zeros("

					"file=[%p], "

					"index=[0x%.16x], "

					"old_end_pos_in_page=[d], "

					"(PAGE_CACHE_SIZE - new_end_pos_in_page"
@@ -117,10 +117,10 @@ int ecryptfs_fill_zeros(struct file *file, loff_t new_length) 
		goto out;

	}

	/* Fill the remainder of the previous last page with zeros */

	rc = write_zeros(file, index, (old_end_pos_in_page + 1),

	rc = ecryptfs_write_zeros(file, index, (old_end_pos_in_page + 1),

			 ((PAGE_CACHE_SIZE - 1) - old_end_pos_in_page));

	if (rc) {

		ecryptfs_printk(KERN_ERR, "write_zeros(file=[%p], "

		ecryptfs_printk(KERN_ERR, "ecryptfs_write_zeros(file=[%p], "

				"index=[0x%.16x], old_end_pos_in_page=[d], "

				"(PAGE_CACHE_SIZE - old_end_pos_in_page)=[d]) "

				"returned [%d]\n", file, index,
@@ -131,9 +131,10 @@ int ecryptfs_fill_zeros(struct file *file, loff_t new_length) 
	index++;

	while (index < new_end_page_index) {

		/* Fill all intermediate pages with zeros */

		rc = write_zeros(file, index, 0, PAGE_CACHE_SIZE);

		rc = ecryptfs_write_zeros(file, index, 0, PAGE_CACHE_SIZE);

		if (rc) {

			ecryptfs_printk(KERN_ERR, "write_zeros(file=[%p], "

			ecryptfs_printk(KERN_ERR, "ecryptfs_write_zeros("

					"file=[%p], "

					"index=[0x%.16x], "

					"old_end_pos_in_page=[d], "

					"(PAGE_CACHE_SIZE - new_end_pos_in_page"
@@ -149,9 +150,9 @@ int ecryptfs_fill_zeros(struct file *file, loff_t new_length) 
	}

	/* Fill the portion at the beginning of the last new page with

	 * zero's */

	rc = write_zeros(file, index, 0, (new_end_pos_in_page + 1));

	rc = ecryptfs_write_zeros(file, index, 0, (new_end_pos_in_page + 1));

	if (rc) {

		ecryptfs_printk(KERN_ERR, "write_zeros(file="

		ecryptfs_printk(KERN_ERR, "ecryptfs_write_zeros(file="

				"[%p], index=[0x%.16x], 0, "

				"new_end_pos_in_page=[%d]"

				"returned [%d]\n", file, index,
@@ -400,7 +401,6 @@ out: 
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)
@@ -408,16 +408,21 @@ 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 (page->index != 0) {

		loff_t end_of_prev_pg_pos =

			(((loff_t)page->index << PAGE_CACHE_SHIFT) - 1);



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

			rc = ecryptfs_truncate(file->f_path.dentry,

					       end_of_prev_pg_pos);

			if (rc) {

				printk(KERN_ERR "Error on attempt to "

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

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

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

				goto out;

			}

		}

	}

out:

	return rc;

}
@@ -753,7 +758,7 @@ out: 
}



/**

 * write_zeros

 * ecryptfs_write_zeros

 * @file: The ecryptfs file

 * @index: The index in which we are writing

 * @start: The position after the last block of data
@@ -763,8 +768,8 @@ out: 
 *

 * (start + num_zeros) must be less than or equal to PAGE_CACHE_SIZE

 */

static

int write_zeros(struct file *file, pgoff_t index, int start, int num_zeros)

int

ecryptfs_write_zeros(struct file *file, pgoff_t index, int start, int num_zeros)

{

	int rc = 0;

	struct page *tmp_page;

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