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eCryptfs: Cleanup and optimize ecryptfs_lookup_interpose()
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ecryptfs_lookup_interpose() has turned into spaghetti code over the
years. This is an effort to clean it up.

 - Shorten overly descriptive variable names such as ecryptfs_dentry
 - Simplify gotos and error paths
 - Create helper function for reading plaintext i_size from metadata

It also includes an optimization when reading i_size from the metadata.
A complete page-sized kmem_cache_alloc() was being done to read in 16
bytes of metadata. The buffer for that is now statically declared.

Signed-off-by: Tyler Hicks <[email protected]>
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Tyler Hicks committed May 29, 2011
1 parent 7a86617 commit 778aeb4
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Showing 3 changed files with 88 additions and 105 deletions.
45 changes: 21 additions & 24 deletions fs/ecryptfs/crypto.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -1201,24 +1201,19 @@ int ecryptfs_cipher_code_to_string(char *str, u8 cipher_code)
return rc;
}

int ecryptfs_read_and_validate_header_region(char *data,
struct inode *ecryptfs_inode)
int ecryptfs_read_and_validate_header_region(struct inode *inode)
{
struct ecryptfs_crypt_stat *crypt_stat =
&(ecryptfs_inode_to_private(ecryptfs_inode)->crypt_stat);
u8 file_size[ECRYPTFS_SIZE_AND_MARKER_BYTES];
u8 *marker = file_size + ECRYPTFS_FILE_SIZE_BYTES;
int rc;

if (crypt_stat->extent_size == 0)
crypt_stat->extent_size = ECRYPTFS_DEFAULT_EXTENT_SIZE;
rc = ecryptfs_read_lower(data, 0, crypt_stat->extent_size,
ecryptfs_inode);
if (rc < 0) {
printk(KERN_ERR "%s: Error reading header region; rc = [%d]\n",
__func__, rc);
goto out;
}
rc = ecryptfs_validate_marker(data + ECRYPTFS_FILE_SIZE_BYTES);
out:
rc = ecryptfs_read_lower(file_size, 0, ECRYPTFS_SIZE_AND_MARKER_BYTES,
inode);
if (rc < ECRYPTFS_SIZE_AND_MARKER_BYTES)
return rc >= 0 ? -EINVAL : rc;
rc = ecryptfs_validate_marker(marker);
if (!rc)
ecryptfs_i_size_init(file_size, inode);
return rc;
}

Expand Down Expand Up @@ -1562,19 +1557,21 @@ int ecryptfs_read_xattr_region(char *page_virt, struct inode *ecryptfs_inode)
return rc;
}

int ecryptfs_read_and_validate_xattr_region(char *page_virt,
int ecryptfs_read_and_validate_xattr_region(struct dentry *dentry,
struct inode *inode)
{
u8 file_size[ECRYPTFS_SIZE_AND_MARKER_BYTES];
u8 *marker = file_size + ECRYPTFS_FILE_SIZE_BYTES;
int rc;

rc = ecryptfs_read_xattr_region(page_virt, inode);
if (rc)
goto out;
rc = ecryptfs_validate_marker(page_virt + ECRYPTFS_FILE_SIZE_BYTES);
if (rc)
printk(KERN_WARNING "Valid data found in [%s] xattr, but "
"the marker is invalid\n", ECRYPTFS_XATTR_NAME);
out:
rc = ecryptfs_getxattr_lower(ecryptfs_dentry_to_lower(dentry),
ECRYPTFS_XATTR_NAME, file_size,
ECRYPTFS_SIZE_AND_MARKER_BYTES);
if (rc < ECRYPTFS_SIZE_AND_MARKER_BYTES)
return rc >= 0 ? -EINVAL : rc;
rc = ecryptfs_validate_marker(marker);
if (!rc)
ecryptfs_i_size_init(file_size, inode);
return rc;
}

Expand Down
7 changes: 4 additions & 3 deletions fs/ecryptfs/ecryptfs_kernel.h
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Original file line number Diff line number Diff line change
Expand Up @@ -200,6 +200,8 @@ ecryptfs_get_key_payload_data(struct key *key)
#define MAGIC_ECRYPTFS_MARKER 0x3c81b7f5
#define MAGIC_ECRYPTFS_MARKER_SIZE_BYTES 8 /* 4*2 */
#define ECRYPTFS_FILE_SIZE_BYTES (sizeof(u64))
#define ECRYPTFS_SIZE_AND_MARKER_BYTES (ECRYPTFS_FILE_SIZE_BYTES \
+ MAGIC_ECRYPTFS_MARKER_SIZE_BYTES)
#define ECRYPTFS_DEFAULT_CIPHER "aes"
#define ECRYPTFS_DEFAULT_KEY_BYTES 16
#define ECRYPTFS_DEFAULT_HASH "md5"
Expand Down Expand Up @@ -659,9 +661,8 @@ int ecryptfs_new_file_context(struct dentry *ecryptfs_dentry);
void ecryptfs_write_crypt_stat_flags(char *page_virt,
struct ecryptfs_crypt_stat *crypt_stat,
size_t *written);
int ecryptfs_read_and_validate_header_region(char *data,
struct inode *ecryptfs_inode);
int ecryptfs_read_and_validate_xattr_region(char *page_virt,
int ecryptfs_read_and_validate_header_region(struct inode *inode);
int ecryptfs_read_and_validate_xattr_region(struct dentry *dentry,
struct inode *inode);
u8 ecryptfs_code_for_cipher_string(char *cipher_name, size_t key_bytes);
int ecryptfs_cipher_code_to_string(char *str, u8 cipher_code);
Expand Down
141 changes: 63 additions & 78 deletions fs/ecryptfs/inode.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -307,105 +307,90 @@ ecryptfs_create(struct inode *directory_inode, struct dentry *ecryptfs_dentry,
return rc;
}

static int ecryptfs_i_size_read(struct dentry *dentry, struct inode *inode)
{
struct ecryptfs_crypt_stat *crypt_stat;
int rc;

rc = ecryptfs_get_lower_file(dentry, inode);
if (rc) {
printk(KERN_ERR "%s: Error attempting to initialize "
"the lower file for the dentry with name "
"[%s]; rc = [%d]\n", __func__,
dentry->d_name.name, rc);
return rc;
}

crypt_stat = &ecryptfs_inode_to_private(inode)->crypt_stat;
/* TODO: lock for crypt_stat comparison */
if (!(crypt_stat->flags & ECRYPTFS_POLICY_APPLIED))
ecryptfs_set_default_sizes(crypt_stat);

rc = ecryptfs_read_and_validate_header_region(inode);
ecryptfs_put_lower_file(inode);
if (rc) {
rc = ecryptfs_read_and_validate_xattr_region(dentry, inode);
if (!rc)
crypt_stat->flags |= ECRYPTFS_METADATA_IN_XATTR;
}

/* Must return 0 to allow non-eCryptfs files to be looked up, too */
return 0;
}

/**
* ecryptfs_lookup_interpose - Dentry interposition for a lookup
*/
static int ecryptfs_lookup_interpose(struct dentry *ecryptfs_dentry,
static int ecryptfs_lookup_interpose(struct dentry *dentry,
struct dentry *lower_dentry,
struct inode *ecryptfs_dir_inode)
struct inode *dir_inode)
{
struct dentry *lower_dir_dentry;
struct inode *inode, *lower_inode = lower_dentry->d_inode;
struct ecryptfs_dentry_info *dentry_info;
struct vfsmount *lower_mnt;
struct inode *inode, *lower_inode;
struct ecryptfs_crypt_stat *crypt_stat;
char *page_virt = NULL;
int put_lower = 0, rc = 0;

lower_dir_dentry = lower_dentry->d_parent;
lower_mnt = mntget(ecryptfs_dentry_to_lower_mnt(
ecryptfs_dentry->d_parent));
lower_inode = lower_dentry->d_inode;
fsstack_copy_attr_atime(ecryptfs_dir_inode, lower_dir_dentry->d_inode);
int rc = 0;

lower_mnt = mntget(ecryptfs_dentry_to_lower_mnt(dentry->d_parent));
fsstack_copy_attr_atime(dir_inode, lower_dentry->d_parent->d_inode);
BUG_ON(!lower_dentry->d_count);
ecryptfs_set_dentry_private(ecryptfs_dentry,
kmem_cache_alloc(ecryptfs_dentry_info_cache,
GFP_KERNEL));
if (!ecryptfs_dentry_to_private(ecryptfs_dentry)) {
rc = -ENOMEM;

dentry_info = kmem_cache_alloc(ecryptfs_dentry_info_cache, GFP_KERNEL);
ecryptfs_set_dentry_private(dentry, dentry_info);
if (!dentry_info) {
printk(KERN_ERR "%s: Out of memory whilst attempting "
"to allocate ecryptfs_dentry_info struct\n",
__func__);
goto out_put;
dput(lower_dentry);
mntput(lower_mnt);
d_drop(dentry);
return -ENOMEM;
}
ecryptfs_set_dentry_lower(ecryptfs_dentry, lower_dentry);
ecryptfs_set_dentry_lower_mnt(ecryptfs_dentry, lower_mnt);
ecryptfs_set_dentry_lower(dentry, lower_dentry);
ecryptfs_set_dentry_lower_mnt(dentry, lower_mnt);

if (!lower_dentry->d_inode) {
/* We want to add because we couldn't find in lower */
d_add(ecryptfs_dentry, NULL);
goto out;
d_add(dentry, NULL);
return 0;
}
inode = __ecryptfs_get_inode(lower_inode, ecryptfs_dir_inode->i_sb);
inode = __ecryptfs_get_inode(lower_inode, dir_inode->i_sb);
if (IS_ERR(inode)) {
rc = PTR_ERR(inode);
printk(KERN_ERR "%s: Error interposing; rc = [%d]\n",
__func__, rc);
goto out;
}
if (!S_ISREG(inode->i_mode)) {
if (inode->i_state & I_NEW)
unlock_new_inode(inode);
d_add(ecryptfs_dentry, inode);
goto out;
}
/* Released in this function */
page_virt = kmem_cache_zalloc(ecryptfs_header_cache_2, GFP_USER);
if (!page_virt) {
printk(KERN_ERR "%s: Cannot kmem_cache_zalloc() a page\n",
__func__);
rc = -ENOMEM;
make_bad_inode(inode);
goto out;
}
rc = ecryptfs_get_lower_file(ecryptfs_dentry, inode);
if (rc) {
printk(KERN_ERR "%s: Error attempting to initialize "
"the lower file for the dentry with name "
"[%s]; rc = [%d]\n", __func__,
ecryptfs_dentry->d_name.name, rc);
make_bad_inode(inode);
goto out_free_kmem;
printk(KERN_ERR "%s: Error interposing; rc = [%ld]\n",
__func__, PTR_ERR(inode));
return PTR_ERR(inode);
}
put_lower = 1;
crypt_stat = &ecryptfs_inode_to_private(inode)->crypt_stat;
/* TODO: lock for crypt_stat comparison */
if (!(crypt_stat->flags & ECRYPTFS_POLICY_APPLIED))
ecryptfs_set_default_sizes(crypt_stat);
rc = ecryptfs_read_and_validate_header_region(page_virt, inode);
if (rc) {
memset(page_virt, 0, PAGE_CACHE_SIZE);
rc = ecryptfs_read_and_validate_xattr_region(page_virt,
inode);
if (S_ISREG(inode->i_mode)) {
rc = ecryptfs_i_size_read(dentry, inode);
if (rc) {
rc = 0;
goto unlock_inode;
make_bad_inode(inode);
return rc;
}
crypt_stat->flags |= ECRYPTFS_METADATA_IN_XATTR;
}
ecryptfs_i_size_init(page_virt, inode);
unlock_inode:

if (inode->i_state & I_NEW)
unlock_new_inode(inode);
d_add(ecryptfs_dentry, inode);
out_free_kmem:
kmem_cache_free(ecryptfs_header_cache_2, page_virt);
goto out;
out_put:
dput(lower_dentry);
mntput(lower_mnt);
d_drop(ecryptfs_dentry);
out:
if (put_lower)
ecryptfs_put_lower_file(inode);
d_add(dentry, inode);

return rc;
}

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