ext4 crypto: reorganize how we store keys in the inode
This is a pretty massive patch which does a number of different things:
1) The per-inode encryption information is now stored in an allocated
data structure, ext4_crypt_info, instead of directly in the node.
This reduces the size usage of an in-memory inode when it is not
using encryption.
2) We drop the ext4_fname_crypto_ctx entirely, and use the per-inode
encryption structure instead. This remove an unnecessary memory
allocation and free for the fname_crypto_ctx as well as allowing us
to reuse the ctfm in a directory for multiple lookups and file
creations.
3) We also cache the inode's policy information in the ext4_crypt_info
structure so we don't have to continually read it out of the
extended attributes.
4) We now keep the keyring key in the inode's encryption structure
instead of releasing it after we are done using it to derive the
per-inode key. This allows us to test to see if the key has been
revoked; if it has, we prevent the use of the derived key and free
it.
5) When an inode is released (or when the derived key is freed), we
will use memset_explicit() to zero out the derived key, so it's not
left hanging around in memory. This implies that when a user logs
out, it is important to first revoke the key, and then unlink it,
and then finally, to use "echo 3 > /proc/sys/vm/drop_caches" to
release any decrypted pages and dcache entries from the system
caches.
6) All this, and we also shrink the number of lines of code by around
100. :-)
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c
index b340643..9bed99f 100644
--- a/fs/ext4/namei.c
+++ b/fs/ext4/namei.c
@@ -607,17 +607,14 @@
char *name;
struct ext4_str fname_crypto_str
= {.name = NULL, .len = 0};
- struct ext4_fname_crypto_ctx *ctx = NULL;
int res;
name = de->name;
len = de->name_len;
- ctx = ext4_get_fname_crypto_ctx(dir,
- EXT4_NAME_LEN);
- if (IS_ERR(ctx)) {
- printk(KERN_WARNING "Error acquiring"
- " crypto ctxt--skipping crypto\n");
- ctx = NULL;
+ res = ext4_setup_fname_crypto(dir);
+ if (res) {
+ printk(KERN_WARNING "Error setting up"
+ " fname crypto: %d\n", res);
}
if (ctx == NULL) {
/* Directory is not encrypted */
@@ -637,7 +634,6 @@
"allocating crypto "
"buffer--skipping "
"crypto\n");
- ext4_put_fname_crypto_ctx(&ctx);
ctx = NULL;
}
res = ext4_fname_disk_to_usr(ctx, NULL, de,
@@ -658,7 +654,6 @@
printk("%*.s:(E)%x.%u ", len, name,
h.hash, (unsigned) ((char *) de
- base));
- ext4_put_fname_crypto_ctx(&ctx);
ext4_fname_crypto_free_buffer(
&fname_crypto_str);
}
@@ -944,7 +939,6 @@
struct buffer_head *bh;
struct ext4_dir_entry_2 *de, *top;
int err = 0, count = 0;
- struct ext4_fname_crypto_ctx *ctx = NULL;
struct ext4_str fname_crypto_str = {.name = NULL, .len = 0}, tmp_str;
dxtrace(printk(KERN_INFO "In htree dirblock_to_tree: block %lu\n",
@@ -959,17 +953,15 @@
EXT4_DIR_REC_LEN(0));
#ifdef CONFIG_EXT4_FS_ENCRYPTION
/* Check if the directory is encrypted */
- ctx = ext4_get_fname_crypto_ctx(dir, EXT4_NAME_LEN);
- if (IS_ERR(ctx)) {
- err = PTR_ERR(ctx);
+ err = ext4_setup_fname_crypto(dir);
+ if (err) {
brelse(bh);
return err;
}
- if (ctx != NULL) {
- err = ext4_fname_crypto_alloc_buffer(ctx, EXT4_NAME_LEN,
+ if (ext4_encrypted_inode(dir)) {
+ err = ext4_fname_crypto_alloc_buffer(dir, EXT4_NAME_LEN,
&fname_crypto_str);
if (err < 0) {
- ext4_put_fname_crypto_ctx(&ctx);
brelse(bh);
return err;
}
@@ -990,8 +982,7 @@
continue;
if (de->inode == 0)
continue;
- if (ctx == NULL) {
- /* Directory is not encrypted */
+ if (!ext4_encrypted_inode(dir)) {
tmp_str.name = de->name;
tmp_str.len = de->name_len;
err = ext4_htree_store_dirent(dir_file,
@@ -1001,7 +992,7 @@
int save_len = fname_crypto_str.len;
/* Directory is encrypted */
- err = ext4_fname_disk_to_usr(ctx, hinfo, de,
+ err = ext4_fname_disk_to_usr(dir, hinfo, de,
&fname_crypto_str);
if (err < 0) {
count = err;
@@ -1021,7 +1012,6 @@
errout:
brelse(bh);
#ifdef CONFIG_EXT4_FS_ENCRYPTION
- ext4_put_fname_crypto_ctx(&ctx);
ext4_fname_crypto_free_buffer(&fname_crypto_str);
#endif
return count;
@@ -3107,7 +3097,6 @@
}
if (encryption_required) {
- struct ext4_fname_crypto_ctx *ctx = NULL;
struct qstr istr;
struct ext4_str ostr;
@@ -3119,19 +3108,14 @@
err = ext4_inherit_context(dir, inode);
if (err)
goto err_drop_inode;
- ctx = ext4_get_fname_crypto_ctx(inode,
- inode->i_sb->s_blocksize);
- if (IS_ERR_OR_NULL(ctx)) {
- /* We just set the policy, so ctx should not be NULL */
- err = (ctx == NULL) ? -EIO : PTR_ERR(ctx);
+ err = ext4_setup_fname_crypto(inode);
+ if (err)
goto err_drop_inode;
- }
istr.name = (const unsigned char *) symname;
istr.len = len;
ostr.name = sd->encrypted_path;
ostr.len = disk_link.len;
- err = ext4_fname_usr_to_disk(ctx, &istr, &ostr);
- ext4_put_fname_crypto_ctx(&ctx);
+ err = ext4_fname_usr_to_disk(inode, &istr, &ostr);
if (err < 0)
goto err_drop_inode;
sd->len = cpu_to_le16(ostr.len);