On Fri, Mar 26, 2021 at 07:08:23PM -0700, Darrick J. Wong wrote: > On Fri, Mar 26, 2021 at 06:43:52PM -0700, harshad shirwadkar wrote: > > 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? > > I bet it wasn't done by design -- afaict all the recovery tools are > totally opportunistic in that /if/ they find something that looks like a > directory entry, /then/ it will pick that up. The names will eventually > get overwritten, so that's the best they can do. > > (I would also wager that people don't like opt-out for new behaviors > unless you're adding it as part of a new feature...) > > --D What about a mount option to enable the filename wipe (with the wiping disabled by default)? > > > [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 > > > > > > > > > > > > > > >
