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eCryptfs: fix write zeros behavior

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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>
This commit is contained in:
Michael Halcrow 2007-06-27 14:09:44 -07:00 committed by Linus Torvalds
parent b75ae86035
commit 240e2df5c7
3 changed files with 50 additions and 24 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
fs/ecryptfs/ecryptfs_kernel.h
View File

@ -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 */

19
fs/ecryptfs/inode.c
View File

@ -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,

53
fs/ecryptfs/mmap.c
View File

@ -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)
@ -408,14 +408,19 @@ 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;
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 @@ 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;