On Fri, Mar 26, 2021 at 4:08 PM Andreas Dilger <adilger@xxxxxxxxx> wrote: > > On Mar 25, 2021, at 12:12 PM, Leah Rumancik <leah.rumancik@xxxxxxxxx> wrote: > > > > Zero out filename field when file is deleted. Also, add mount option > > nowipe_filename to disable this filename wipeout if desired. > > I would personally be against "wipe out entries on delete" as the default > behavior. I think most users would prefer that their data is maximally > recoverable, rather than the minimal security benefit of erasing deleted > content by default. I understand that persistence of filenames provides recoverability that users might like but I feel like that may break sooner or later. For example, if we get directory shrinking patches[1] merged in or if we redesign the directory htree using generic btrees (which will hopefully support shrinking), this kind of recovery will become very hard. Also, I was wondering if persistence of file names was by design? or it was there due to the way we implemented directories? [1] https://patchwork.ozlabs.org/project/linux-ext4/list/?series=166560 Thanks, Harshad > > I think that Darrick made a good point that using the EXT4_SECRM_FL on > the inode gives users a good option to enable/disable this on a per > file or directory basis. > > > Signed-off-by: Leah Rumancik <leah.rumancik@xxxxxxxxx> > > --- > > 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 > > > > > Cheers, Andreas > > > > >
