Patchwork eCryptfs: Make truncate path killable

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Submitter Colin King
Date March 5, 2012, 4:48 p.m.
Message ID <1330966099-11986-2-git-send-email-colin.king@canonical.com>
Download mbox | patch
Permalink /patch/144713/
State New
Headers show

Comments

Colin King - March 5, 2012, 4:48 p.m.
From: Tyler Hicks <tyhicks@canonical.com>

BugLink: http://bugs.launchpad.net/bugs/947270

ecryptfs_write() handles the truncation of eCryptfs inodes. It grabs a
page, zeroes out the appropriate portions, and then encrypts the page
before writing it to the lower filesystem. It was unkillable and due to
the lack of sparse file support could result in tying up a large portion
of system resources, while encrypting pages of zeros, with no way for
the truncate operation to be stopped from userspace.

This patch adds the ability for ecryptfs_write() to detect a pending
fatal signal and return as gracefully as possible. The intent is to
leave the lower file in a useable state, while still allowing a user to
break out of the encryption loop. If a pending fatal signal is detected,
the eCryptfs inode size is updated to reflect the modified inode size
and then -EINTR is returned.

Signed-off-by: Tyler Hicks <tyhicks@canonical.com>
(cherry picked from commit 5e6f0d769017cc49207ef56996e42363ec26c1f0)
Signed-off-by: Colin Ian King <colin.king@canonical.com>

Cc: <stable@vger.kernel.org>
---
 fs/ecryptfs/read_write.c |   19 ++++++++++++++-----
 1 files changed, 14 insertions(+), 5 deletions(-)

Patch

diff --git a/fs/ecryptfs/read_write.c b/fs/ecryptfs/read_write.c
index ec3d936..608c1c3 100644
--- a/fs/ecryptfs/read_write.c
+++ b/fs/ecryptfs/read_write.c
@@ -132,6 +132,11 @@  int ecryptfs_write(struct inode *ecryptfs_inode, char *data, loff_t offset,
 		size_t num_bytes = (PAGE_CACHE_SIZE - start_offset_in_page);
 		loff_t total_remaining_bytes = ((offset + size) - pos);
 
+		if (fatal_signal_pending(current)) {
+			rc = -EINTR;
+			break;
+		}
+
 		if (num_bytes > total_remaining_bytes)
 			num_bytes = total_remaining_bytes;
 		if (pos < offset) {
@@ -193,15 +198,19 @@  int ecryptfs_write(struct inode *ecryptfs_inode, char *data, loff_t offset,
 		}
 		pos += num_bytes;
 	}
-	if ((offset + size) > ecryptfs_file_size) {
-		i_size_write(ecryptfs_inode, (offset + size));
+	if (pos > ecryptfs_file_size) {
+		i_size_write(ecryptfs_inode, pos);
 		if (crypt_stat->flags & ECRYPTFS_ENCRYPTED) {
-			rc = ecryptfs_write_inode_size_to_metadata(
+			int rc2;
+
+			rc2 = ecryptfs_write_inode_size_to_metadata(
 								ecryptfs_inode);
-			if (rc) {
+			if (rc2) {
 				printk(KERN_ERR	"Problem with "
 				       "ecryptfs_write_inode_size_to_metadata; "
-				       "rc = [%d]\n", rc);
+				       "rc = [%d]\n", rc2);
+				if (!rc)
+					rc = rc2;
 				goto out;
 			}
 		}