ext4: disable fast-commit of encrypted dir operations

fast-commit of create, link, and unlink operations in encrypted
directories is completely broken because the unencrypted filenames are
being written to the fast-commit journal instead of the encrypted
filenames.  These operations can't be replayed, as encryption keys
aren't present at journal replay time.  It is also an information leak.

Until if/when we can get this working properly, make encrypted directory
operations ineligible for fast-commit.

Note that fast-commit operations on encrypted regular files continue to
be allowed, as they seem to work.

Fixes: aa75f4d3daae ("ext4: main fast-commit commit path")
Cc: <stable@vger.kernel.org> # v5.10+
Signed-off-by: Eric Biggers <ebiggers@google.com>
Link: https://lore.kernel.org/r/20221106224841.279231-2-ebiggers@kernel.org
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

2 files changed, 26 insertions, 16 deletions

diff --git a/fs/ext4/fast_commit.c b/fs/ext4/fast_commit.c
index 0f6d0a80467d..6d98f2b39b77 100644
--- a/fs/ext4/fast_commit.c
+++ b/fs/ext4/fast_commit.c
@@ -420,25 +420,34 @@ static int __track_dentry_update(struct inode *inode, void *arg, bool update)
 	struct __track_dentry_update_args *dentry_update =
 		(struct __track_dentry_update_args *)arg;
 	struct dentry *dentry = dentry_update->dentry;
-	struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
+	struct inode *dir = dentry->d_parent->d_inode;
+	struct super_block *sb = inode->i_sb;
+	struct ext4_sb_info *sbi = EXT4_SB(sb);
 
 	mutex_unlock(&ei->i_fc_lock);
+
+	if (IS_ENCRYPTED(dir)) {
+		ext4_fc_mark_ineligible(sb, EXT4_FC_REASON_ENCRYPTED_FILENAME,
+					NULL);
+		mutex_lock(&ei->i_fc_lock);
+		return -EOPNOTSUPP;
+	}
+
 	node = kmem_cache_alloc(ext4_fc_dentry_cachep, GFP_NOFS);
 	if (!node) {
-		ext4_fc_mark_ineligible(inode->i_sb, EXT4_FC_REASON_NOMEM, NULL);
+		ext4_fc_mark_ineligible(sb, EXT4_FC_REASON_NOMEM, NULL);
 		mutex_lock(&ei->i_fc_lock);
 		return -ENOMEM;
 	}
 
 	node->fcd_op = dentry_update->op;
-	node->fcd_parent = dentry->d_parent->d_inode->i_ino;
+	node->fcd_parent = dir->i_ino;
 	node->fcd_ino = inode->i_ino;
 	if (dentry->d_name.len > DNAME_INLINE_LEN) {
 		node->fcd_name.name = kmalloc(dentry->d_name.len, GFP_NOFS);
 		if (!node->fcd_name.name) {
 			kmem_cache_free(ext4_fc_dentry_cachep, node);
-			ext4_fc_mark_ineligible(inode->i_sb,
-				EXT4_FC_REASON_NOMEM, NULL);
+			ext4_fc_mark_ineligible(sb, EXT4_FC_REASON_NOMEM, NULL);
 			mutex_lock(&ei->i_fc_lock);
 			return -ENOMEM;
 		}
@@ -2249,17 +2258,17 @@ void ext4_fc_init(struct super_block *sb, journal_t *journal)
 	journal->j_fc_cleanup_callback = ext4_fc_cleanup;
 }
 
-static const char *fc_ineligible_reasons[] = {
-	"Extended attributes changed",
-	"Cross rename",
-	"Journal flag changed",
-	"Insufficient memory",
-	"Swap boot",
-	"Resize",
-	"Dir renamed",
-	"Falloc range op",
-	"Data journalling",
-	"FC Commit Failed"
+static const char * const fc_ineligible_reasons[] = {
+	[EXT4_FC_REASON_XATTR] = "Extended attributes changed",
+	[EXT4_FC_REASON_CROSS_RENAME] = "Cross rename",
+	[EXT4_FC_REASON_JOURNAL_FLAG_CHANGE] = "Journal flag changed",
+	[EXT4_FC_REASON_NOMEM] = "Insufficient memory",
+	[EXT4_FC_REASON_SWAP_BOOT] = "Swap boot",
+	[EXT4_FC_REASON_RESIZE] = "Resize",
+	[EXT4_FC_REASON_RENAME_DIR] = "Dir renamed",
+	[EXT4_FC_REASON_FALLOC_RANGE] = "Falloc range op",
+	[EXT4_FC_REASON_INODE_JOURNAL_DATA] = "Data journalling",
+	[EXT4_FC_REASON_ENCRYPTED_FILENAME] = "Encrypted filename",
 };
 
 int ext4_fc_info_show(struct seq_file *seq, void *v)
diff --git a/fs/ext4/fast_commit.h b/fs/ext4/fast_commit.h
index a6154c3ed135..256f2ad27204 100644
--- a/fs/ext4/fast_commit.h
+++ b/fs/ext4/fast_commit.h
@@ -96,6 +96,7 @@ enum {
 	EXT4_FC_REASON_RENAME_DIR,
 	EXT4_FC_REASON_FALLOC_RANGE,
 	EXT4_FC_REASON_INODE_JOURNAL_DATA,
+	EXT4_FC_REASON_ENCRYPTED_FILENAME,
 	EXT4_FC_REASON_MAX
 };