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From:   Leah Rumancik <leah.rumancik@gmail.com>
To:     linux-ext4@vger.kernel.org
Cc:     tytso@mit.edu, Leah Rumancik <leah.rumancik@gmail.com>
Subject: [PATCH 1/2] ext4: wipe filename upon file deletion
Date:   Thu, 25 Mar 2021 18:12:19 +0000
Message-Id: <20210325181220.1118705-1-leah.rumancik@gmail.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

Zero out filename field when file is deleted. Also, add mount option
nowipe_filename to disable this filename wipeout if desired.

Signed-off-by: Leah Rumancik <leah.rumancik@gmail.com>
---
 fs/ext4/ext4.h  |  1 +
 fs/ext4/namei.c |  4 ++++
 fs/ext4/super.c | 11 ++++++++++-
 3 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 826a56e3bbd2..8011418176bc 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -1247,6 +1247,7 @@ struct ext4_inode_info {
 #define EXT4_MOUNT2_JOURNAL_FAST_COMMIT	0x00000010 /* Journal fast commit */
 #define EXT4_MOUNT2_DAX_NEVER		0x00000020 /* Do not allow Direct Access */
 #define EXT4_MOUNT2_DAX_INODE		0x00000040 /* For printing options only */
+#define EXT4_MOUNT2_WIPE_FILENAME       0x00000080 /* Wipe filename on del entry */
 
 
 #define clear_opt(sb, opt)		EXT4_SB(sb)->s_mount_opt &= \
diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c
index 883e2a7cd4ab..ae6ecabd4d97 100644
--- a/fs/ext4/namei.c
+++ b/fs/ext4/namei.c
@@ -2492,6 +2492,10 @@ int ext4_generic_delete_entry(struct inode *dir,
 			else
 				de->inode = 0;
 			inode_inc_iversion(dir);
+
+			if (test_opt2(dir->i_sb, WIPE_FILENAME))
+				memset(de_del->name, 0, de_del->name_len);
+
 			return 0;
 		}
 		i += ext4_rec_len_from_disk(de->rec_len, blocksize);
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index b9693680463a..5e8737b3f171 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -1688,7 +1688,7 @@ enum {
 	Opt_dioread_nolock, Opt_dioread_lock,
 	Opt_discard, Opt_nodiscard, Opt_init_itable, Opt_noinit_itable,
 	Opt_max_dir_size_kb, Opt_nojournal_checksum, Opt_nombcache,
-	Opt_prefetch_block_bitmaps,
+	Opt_prefetch_block_bitmaps, Opt_nowipe_filename,
 #ifdef CONFIG_EXT4_DEBUG
 	Opt_fc_debug_max_replay, Opt_fc_debug_force
 #endif
@@ -1787,6 +1787,7 @@ static const match_table_t tokens = {
 	{Opt_test_dummy_encryption, "test_dummy_encryption"},
 	{Opt_inlinecrypt, "inlinecrypt"},
 	{Opt_nombcache, "nombcache"},
+	{Opt_nowipe_filename, "nowipe_filename"},
 	{Opt_nombcache, "no_mbcache"},	/* for backward compatibility */
 	{Opt_prefetch_block_bitmaps, "prefetch_block_bitmaps"},
 	{Opt_removed, "check=none"},	/* mount option from ext2/3 */
@@ -2007,6 +2008,8 @@ static const struct mount_opts {
 	{Opt_max_dir_size_kb, 0, MOPT_GTE0},
 	{Opt_test_dummy_encryption, 0, MOPT_STRING},
 	{Opt_nombcache, EXT4_MOUNT_NO_MBCACHE, MOPT_SET},
+	{Opt_nowipe_filename, EXT4_MOUNT2_WIPE_FILENAME, MOPT_CLEAR | MOPT_2 |
+		MOPT_EXT4_ONLY},
 	{Opt_prefetch_block_bitmaps, EXT4_MOUNT_PREFETCH_BLOCK_BITMAPS,
 	 MOPT_SET},
 #ifdef CONFIG_EXT4_DEBUG
@@ -2621,6 +2624,10 @@ static int _ext4_show_options(struct seq_file *seq, struct super_block *sb,
 	} else if (test_opt2(sb, DAX_INODE)) {
 		SEQ_OPTS_PUTS("dax=inode");
 	}
+
+	if (!test_opt2(sb, WIPE_FILENAME))
+		SEQ_OPTS_PUTS("nowipe_filename");
+
 	ext4_show_quota_options(seq, sb);
 	return 0;
 }
@@ -4161,6 +4168,8 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
 	if (def_mount_opts & EXT4_DEFM_DISCARD)
 		set_opt(sb, DISCARD);
 
+	set_opt2(sb, WIPE_FILENAME);
+
 	sbi->s_resuid = make_kuid(&init_user_ns, le16_to_cpu(es->s_def_resuid));
 	sbi->s_resgid = make_kgid(&init_user_ns, le16_to_cpu(es->s_def_resgid));
 	sbi->s_commit_interval = JBD2_DEFAULT_MAX_COMMIT_AGE * HZ;
-- 
2.31.0.291.g576ba9dcdaf-goog