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eCryptfs: Make truncate path killable
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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>
Cc: <stable@vger.kernel.org>
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Tyler Hicks committed Jan 25, 2012
1 parent 684a3ff commit 5e6f0d7
Showing 1 changed file with 14 additions and 5 deletions.
19 changes: 14 additions & 5 deletions fs/ecryptfs/read_write.c
Original file line number Diff line number Diff line change
Expand Up @@ -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) {
Expand Down Expand Up @@ -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;
}
}
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