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: Michael Halcrow <mhalcrow@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/fs/ecryptfs/mmap.c b/fs/ecryptfs/mmap.c
index 55cec98..6df410c 100644
--- a/fs/ecryptfs/mmap.c
+++ b/fs/ecryptfs/mmap.c
@@ -56,9 +56,6 @@
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 @@
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 @@
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 @@
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 @@
}
/* 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 @@
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)
@@ -408,14 +408,19 @@
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;
+ 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", end_of_prev_pg_pos, rc);
+ goto out;
+ }
}
}
out:
@@ -753,7 +758,7 @@
}
/**
- * 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 @@
*
* (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;