[PATCH 1/2] ext4 crypto: use a jbd2 transaction when adding a crypto policy

[PATCH 1/2] ext4 crypto: use a jbd2 transaction when adding a crypto policy

[Theodore Ts'o]

Start a jbd2 transaction, and mark the inode dirty on the inode under
that transaction after setting the encrypt flag.  Otherwise if the
directory isn't modified after setting the crypto policy, the
encrypted flag might not survive the inode getting pushed out from
memory, or the the file system getting unmounted and remounted.

Signed-off-by: Theodore Ts'o <tytso@mit.edu>
---
 fs/ext4/crypto_policy.c | 17 +++++++++++++++--
 1 file changed, 15 insertions(+), 2 deletions(-)

diff --git a/fs/ext4/crypto_policy.c b/fs/ext4/crypto_policy.c
index 02c4e5d..a640ec2 100644
--- a/fs/ext4/crypto_policy.c
+++ b/fs/ext4/crypto_policy.c
@@ -12,6 +12,7 @@
 #include <linux/string.h>
 #include <linux/types.h>
 
+#include "ext4_jbd2.h"
 #include "ext4.h"
 #include "xattr.h"
 
@@ -49,7 +50,8 @@ static int ext4_create_encryption_context_from_policy(
 	struct inode *inode, const struct ext4_encryption_policy *policy)
 {
 	struct ext4_encryption_context ctx;
-	int res = 0;
+	handle_t *handle;
+	int res, res2;
 
 	res = ext4_convert_inline_data(inode);
 	if (res)
@@ -78,11 +80,22 @@ static int ext4_create_encryption_context_from_policy(
 	BUILD_BUG_ON(sizeof(ctx.nonce) != EXT4_KEY_DERIVATION_NONCE_SIZE);
 	get_random_bytes(ctx.nonce, EXT4_KEY_DERIVATION_NONCE_SIZE);
 
+	handle = ext4_journal_start(inode, EXT4_HT_MISC,
+				    ext4_jbd2_credits_xattr(inode));
+	if (IS_ERR(handle))
+		return PTR_ERR(handle);
 	res = ext4_xattr_set(inode, EXT4_XATTR_INDEX_ENCRYPTION,
 			     EXT4_XATTR_NAME_ENCRYPTION_CONTEXT, &ctx,
 			     sizeof(ctx), 0);
-	if (!res)
+	if (!res) {
 		ext4_set_inode_flag(inode, EXT4_INODE_ENCRYPT);
+		res = ext4_mark_inode_dirty(handle, inode);
+		if (res)
+			EXT4_ERROR_INODE(inode, "Failed to mark inode dirty");
+	}
+	res2 = ext4_journal_stop(handle);
+	if (!res)
+		res = res2;
 	return res;
 }
 
-- 
2.3.0

[PATCH 2/2] ext4 crypto: check for too-short encrypted file names

[Theodore Ts'o]

An encrypted file name should never be shorter than an 16 bytes, the
AES block size.  The 3.10 crypto layer will oops and crash the kernel
if ciphertext shorter than the block size is passed to it.

Fortunately, in modern kernels the crypto layer will not crash the
kernel in this scenario, but nevertheless, it represents a corrupted
directory, and we should detect it and mark the file system as
corrupted so that e2fsck can fix this.

Signed-off-by: Theodore Ts'o <tytso@mit.edu>
---
 fs/ext4/crypto_fname.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/fs/ext4/crypto_fname.c b/fs/ext4/crypto_fname.c
index 7dc4eb5..86ee996 100644
--- a/fs/ext4/crypto_fname.c
+++ b/fs/ext4/crypto_fname.c
@@ -329,6 +329,10 @@ int _ext4_fname_disk_to_usr(struct inode *inode,
 			return oname->len;
 		}
 	}
+	if (iname->len < EXT4_CRYPTO_BLOCK_SIZE) {
+		EXT4_ERROR_INODE(inode, "encrypted inode too small");
+		return -EUCLEAN;
+	}
 	if (EXT4_I(inode)->i_crypt_info)
 		return ext4_fname_decrypt(inode, iname, oname);
 
-- 
2.3.0