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/ecryptfs_kernel.h b/fs/ecryptfs/ecryptfs_kernel.h
index 403e3bad1455ae95a079a919306ecfe13cf73793..1b9dd9a96f190b08279cb118a2cad75ecf0b67cd 100644 (file)
--- a/fs/ecryptfs/ecryptfs_kernel.h
+++ b/fs/ecryptfs/ecryptfs_kernel.h
@@ -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 */

diff --git a/fs/ecryptfs/inode.c b/fs/ecryptfs/inode.c
index 1548be26b5e61060ee5c5eb440209bd98b850724..0981ae35ea164531ae0f127dbb6de120d7a7f56c 100644 (file)
--- a/fs/ecryptfs/inode.c
+++ b/fs/ecryptfs/inode.c
@@ -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,

diff --git a/fs/ecryptfs/mmap.c b/fs/ecryptfs/mmap.c
index 55cec98a84e75cf490143af46302a9495993f158..6df410c7726471c28b493c9d2b91f61ca6072696 100644 (file)
--- a/fs/ecryptfs/mmap.c
+++ b/fs/ecryptfs/mmap.c
@@ -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;