[PATCH 1/2] eCryptfs: fix write zeros behavior

[PATCH 1/2] eCryptfs: fix write zeros behavior

[Michael Halcrow]

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>

---
 fs/ecryptfs/ecryptfs_kernel.h |    2 +
 fs/ecryptfs/inode.c           |   19 ++++++++++++++
 fs/ecryptfs/mmap.c            |   53 ++++++++++++++++++++++------------------
 3 files changed, 50 insertions(+), 24 deletions(-)

diff --git a/fs/ecryptfs/ecryptfs_kernel.h b/fs/ecryptfs/ecryptfs_kernel.h
index 403e3ba..1b9dd9a 100644
--- 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 1548be2..0981ae3 100644
--- 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 55cec98..6df410c 100644
--- 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;
-- 
1.4.4.4

[PATCH 2/2] eCryptfs: initialize crypt_stat in setattr

[Michael Halcrow]

Recent changes in eCryptfs have made it possible to get to
ecryptfs_setattr() with an uninitialized crypt_stat struct. This
results in a wide and colorful variety of unpleasantries. This patch
properly initializes the crypt_stat structure in ecryptfs_setattr()
when it is necessary to do so.

Signed-off-by: Michael Halcrow <mhalcrow@us.ibm.com>

diff --git a/fs/ecryptfs/inode.c b/fs/ecryptfs/inode.c
index 0981ae3..83e94fe 100644
--- a/fs/ecryptfs/inode.c
+++ b/fs/ecryptfs/inode.c
@@ -894,9 +894,54 @@ static int ecryptfs_setattr(struct dentry *dentry, struct iattr *ia)
 	struct ecryptfs_crypt_stat *crypt_stat;
 
 	crypt_stat = &ecryptfs_inode_to_private(dentry->d_inode)->crypt_stat;
-	lower_dentry = ecryptfs_dentry_to_lower(dentry);
+	if (!(crypt_stat->flags & ECRYPTFS_STRUCT_INITIALIZED))
+		ecryptfs_init_crypt_stat(crypt_stat);
 	inode = dentry->d_inode;
 	lower_inode = ecryptfs_inode_to_lower(inode);
+	lower_dentry = ecryptfs_dentry_to_lower(dentry);
+	mutex_lock(&crypt_stat->cs_mutex);
+	if (S_ISDIR(dentry->d_inode->i_mode))
+		crypt_stat->flags &= ~(ECRYPTFS_ENCRYPTED);
+	else if (!(crypt_stat->flags & ECRYPTFS_POLICY_APPLIED)
+		 || !(crypt_stat->flags & ECRYPTFS_KEY_VALID)) {
+		struct vfsmount *lower_mnt;
+		struct file *lower_file = NULL;
+		struct ecryptfs_mount_crypt_stat *mount_crypt_stat;
+		int lower_flags;
+
+		lower_mnt = ecryptfs_dentry_to_lower_mnt(dentry);
+		lower_flags = O_RDONLY;
+		if ((rc = ecryptfs_open_lower_file(&lower_file, lower_dentry,
+						   lower_mnt, lower_flags))) {
+			printk(KERN_ERR
+			       "Error opening lower file; rc = [%d]\n", rc);
+			mutex_unlock(&crypt_stat->cs_mutex);
+			goto out;
+		}
+		mount_crypt_stat = &ecryptfs_superblock_to_private(
+			dentry->d_sb)->mount_crypt_stat;
+		if ((rc = ecryptfs_read_metadata(dentry, lower_file))) {
+			if (!(mount_crypt_stat->flags
+			      & ECRYPTFS_PLAINTEXT_PASSTHROUGH_ENABLED)) {
+				rc = -EIO;
+				printk(KERN_WARNING "Attempt to read file that "
+				       "is not in a valid eCryptfs format, "
+				       "and plaintext passthrough mode is not "
+				       "enabled; returning -EIO\n");
+
+				mutex_unlock(&crypt_stat->cs_mutex);
+				fput(lower_file);
+				goto out;
+			}
+			rc = 0;
+			crypt_stat->flags &= ~(ECRYPTFS_ENCRYPTED);
+			mutex_unlock(&crypt_stat->cs_mutex);
+			fput(lower_file);
+			goto out;
+		}
+		fput(lower_file);
+	}
+	mutex_unlock(&crypt_stat->cs_mutex);
 	if (ia->ia_valid & ATTR_SIZE) {
 		ecryptfs_printk(KERN_DEBUG,
 				"ia->ia_valid = [0x%x] ATTR_SIZE" " = [0x%x]\n",

[PATCH] eCryptfs: zero out last page for llseek/write

[Michael Halcrow]

When one llseek's past the end of the file and then writes, every page
past the previous end of the file should be cleared. Trevor found that
the code, as is, does not assure that the very last page is always
cleared. This patch takes care of that.

This patch, including the two that I sent on June 13th, are bugfixes
to try to clean up the recent llseek() hack job; hopefully they can be
merged before the release of 2.6.22 (I've noticed that we're already
at -rc6).

Signed-off-by: Michael Halcrow <mhalcrow@us.ibm.com>

---
 fs/ecryptfs/mmap.c |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)

diff --git a/fs/ecryptfs/mmap.c b/fs/ecryptfs/mmap.c
index 6df410c..7d5a43c 100644
--- a/fs/ecryptfs/mmap.c
+++ b/fs/ecryptfs/mmap.c
@@ -422,6 +422,8 @@ static int ecryptfs_prepare_write(struct file *file, struct page *page,
 				goto out;
 			}
 		}
+		if (end_of_prev_pg_pos + 1 > i_size_read(page->mapping->host))
+			zero_user_page(page, 0, PAGE_CACHE_SIZE, KM_USER0);
 	}
 out:
 	return rc;
-- 
1.4.4.4