e2fsprogs: fix and document the stable_inodes feature

PATCH In review Eric Biggers 3 participants 20 messages Apr 1, 2020 – Sep 21, 2020 fscrypt: file system level encryption support

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Eric Biggers

author maintainer

2020-04-01 20:34 UTC #0 lore raw

cover e2fsprogs: fix and document the stable_inodes feature

Fix tune2fs to not allow cases where IV_INO_LBLK_64-encrypted files (which can exist if the stable_inodes feature is set) could be broken:

- Changing the filesystem's UUID
- Clearing the stable_inodes feature

Also document the stable_inodes feature in the appropriate places.

Eric Biggers (4):
tune2fs: prevent changing UUID of fs with stable_inodes feature
tune2fs: prevent stable_inodes feature from being cleared ext4.5: document the stable_inodes feature
tune2fs.8: document the stable_inodes feature

 misc/ext4.5.in    | 16 ++++++++++++++++
 misc/tune2fs.8.in |  7 +++++++
 misc/tune2fs.c    | 10 ++++++++--
 3 files changed, 31 insertions(+), 2 deletions(-)

Signature · 1 line

2.26.0.rc2.310.g2932bb562d-goog

Eric Biggers

author maintainer

2020-04-01 20:35 UTC #1 lore raw

PATCH 1/4 tune2fs: prevent changing UUID of fs with stable_inodes feature

From: Eric Biggers <[email protected]>

The stable_inodes feature is intended to indicate that it's safe to use IV_INO_LBLK_64 encryption policies, where the encryption depends on the inode numbers and thus filesystem shrinking is not allowed. However since inode numbers are not unique across filesystems, the encryption also depends on the filesystem UUID, and I missed that there is a supported way to change the filesystem UUID (tune2fs -U).

So, make 'tune2fs -U' report an error if stable_inodes is set.

We could add a separate stable_uuid feature flag, but it seems unlikely it would be useful enough on its own to warrant another flag.

Signed-off-by Eric Biggers <[email protected]>

---
 misc/tune2fs.c | 7 +++++++
 1 file changed, 7 insertions(+)

misc/tune2fs.c +7 -0

index 314cc0d0..ca06c98b 100644
@@ -3236,6 +3236,13 @@ _("Warning: The journal is dirty. You may wish to replay the journal like:\n\n"
 		char buf[SUPERBLOCK_SIZE] __attribute__ ((aligned(8)));
 		__u8 old_uuid[UUID_SIZE];
 
+		if (ext2fs_has_feature_stable_inodes(fs->super)) {
+			fputs(_("Cannot change the UUID of this filesystem "
+				"because it has the stable_inodes feature "
+				"flag.\n"), stderr);
+			exit(1);
+		}
+
 		if (!ext2fs_has_feature_csum_seed(fs->super) &&
 		    (ext2fs_has_feature_metadata_csum(fs->super) ||
 		     ext2fs_has_feature_ea_inode(fs->super))) {

Signature · 1 line

2.26.0.rc2.310.g2932bb562d-goog

Andreas Dilger

2020-04-02 02:19 UTC #2 lore raw

Re: [PATCH 1/4] tune2fs: prevent changing UUID of fs with stable_inodes feature

Quoted 10 lines · Eric Biggers

From: Eric Biggers <[email protected]>
The stable_inodes feature is intended to indicate that it's safe to use IV_INO_LBLK_64 encryption policies, where the encryption depends on the inode numbers and thus filesystem shrinking is not allowed. However since inode numbers are not unique across filesystems, the encryption also depends on the filesystem UUID, and I missed that there is a supported way to change the filesystem UUID (tune2fs -U).

Quoted 4 lines

So, make 'tune2fs -U' report an error if stable_inodes is set.
We could add a separate stable_uuid feature flag, but it seems unlikely it would be useful enough on its own to warrant another flag.

What about having tune2fs walk the inode table checking for any inodes that have this flag, and only refusing to clear the flag if it finds any? That takes some time on very large filesystems, but since inode table reading is linear it is reasonable on most filesystems.

Cheers, Andreas

Quoted 24 lines

Signed-off-by Eric Biggers <[email protected]>

---
misc/tune2fs.c | 7 +++++++

1 file changed, 7 insertions(+)

misc/tune2fs.c +7 -1

index 314cc0d0..ca06c98b 100644
@@ -3236,6 +3236,13 @@ _("Warning: The journal is dirty. You may wish to replay the journal like:\n\n"
 		char buf[SUPERBLOCK_SIZE] __attribute__ ((aligned(8)));
 		__u8 old_uuid[UUID_SIZE];
 
+		if (ext2fs_has_feature_stable_inodes(fs->super)) {
+			fputs(_("Cannot change the UUID of this filesystem "
+				"because it has the stable_inodes feature "
+				"flag.\n"), stderr);
+			exit(1);
+		}
+
 		if (!ext2fs_has_feature_csum_seed(fs->super) &&
 		    (ext2fs_has_feature_metadata_csum(fs->super) ||
 		     ext2fs_has_feature_ea_inode(fs->super))) {
--

Quoted 2 lines

2.26.0.rc2.310.g2932bb562d-goog

Cheers, Andreas

Eric Biggers

author maintainer

2020-04-07 05:32 UTC #3 lore raw

Re: [PATCH 1/4] tune2fs: prevent changing UUID of fs with stable_inodes feature

Quoted 13 lines · Andreas Dilger

Quoted 12 lines · Eric Biggers
From: Eric Biggers <[email protected]>
The stable_inodes feature is intended to indicate that it's safe to use IV_INO_LBLK_64 encryption policies, where the encryption depends on the inode numbers and thus filesystem shrinking is not allowed. However since inode numbers are not unique across filesystems, the encryption also depends on the filesystem UUID, and I missed that there is a supported way to change the filesystem UUID (tune2fs -U).
So, make 'tune2fs -U' report an error if stable_inodes is set.

Quoted 8 lines

Quoted 2 lines
We could add a separate stable_uuid feature flag, but it seems unlikely it would be useful enough on its own to warrant another flag.
What about having tune2fs walk the inode table checking for any inodes that have this flag, and only refusing to clear the flag if it finds any? That takes some time on very large filesystems, but since inode table reading is linear it is reasonable on most filesystems.

I assume you meant to make this comment on patch 2, "tune2fs: prevent stable_inodes feature from being cleared"?

It's a good suggestion, but it also applies equally to the encrypt, verity, extents, and ea_inode features. Currently tune2fs can't clear any of these, since any inode might be using them.

Note that it would actually be slightly harder to implement your suggestion for stable_inodes than those four existing features, since clearing stable_inodes would require reading xattrs rather than just the inode flags.

So if I have time, I can certainly look into allowing tune2fs to clear the encrypt, verity, extents, stable_inodes, and ea_inode features, by doing an inode table scan to verify that it's safe. IMO it doesn't make sense to hold up this patch on it, though. This patch just makes stable_inodes work like other ext4 features.

- Eric

Andreas Dilger

2020-04-07 16:19 UTC #4 lore raw

Re: [PATCH 1/4] tune2fs: prevent changing UUID of fs with stable_inodes feature

Quoted 36 lines · Eric Biggers

Quoted 13 lines · Andreas Dilger
Quoted 12 lines · Eric Biggers
From: Eric Biggers <[email protected]>
The stable_inodes feature is intended to indicate that it's safe to use IV_INO_LBLK_64 encryption policies, where the encryption depends on the inode numbers and thus filesystem shrinking is not allowed. However since inode numbers are not unique across filesystems, the encryption also depends on the filesystem UUID, and I missed that there is a supported way to change the filesystem UUID (tune2fs -U).
So, make 'tune2fs -U' report an error if stable_inodes is set.
Quoted 7 lines
Quoted 2 lines
We could add a separate stable_uuid feature flag, but it seems unlikely it would be useful enough on its own to warrant another flag.
What about having tune2fs walk the inode table checking for any inodes that have this flag, and only refusing to clear the flag if it finds any? That takes some time on very large filesystems, but since inode table reading is linear it is reasonable on most filesystems.
I assume you meant to make this comment on patch 2, "tune2fs: prevent stable_inodes feature from being cleared"?
It's a good suggestion, but it also applies equally to the encrypt, verity, extents, and ea_inode features. Currently tune2fs can't clear any of these, since any inode might be using them.
Note that it would actually be slightly harder to implement your suggestion for stable_inodes than those four existing features, since clearing stable_inodes would require reading xattrs rather than just the inode flags.

Quoted 5 lines

So if I have time, I can certainly look into allowing tune2fs to clear the encrypt, verity, extents, stable_inodes, and ea_inode features, by doing an inode table scan to verify that it's safe. IMO it doesn't make sense to hold up this patch on it, though. This patch just makes stable_inodes work like other ext4 features.

Sure, I'm OK with this patch, since it avoids accidental breakage.

One question though - for the data checksums it uses s_checksum_seed to generate checksums, rather than directly using the UUID itself, so that it *is* possible to change the filesystem UUID after metadata_csum is in use, without the need to rewrite all of the checksums in the filesystem. Could the same be done for stable_inode?

Cheers, Andreas

Eric Biggers

author maintainer

2020-04-08 03:11 UTC #5 lore raw

Re: [PATCH 1/4] tune2fs: prevent changing UUID of fs with stable_inodes feature

Quoted 42 lines · Andreas Dilger

Quoted 36 lines · Eric Biggers
Quoted 13 lines · Andreas Dilger
Quoted 12 lines · Eric Biggers
From: Eric Biggers <[email protected]>
The stable_inodes feature is intended to indicate that it's safe to use IV_INO_LBLK_64 encryption policies, where the encryption depends on the inode numbers and thus filesystem shrinking is not allowed. However since inode numbers are not unique across filesystems, the encryption also depends on the filesystem UUID, and I missed that there is a supported way to change the filesystem UUID (tune2fs -U).
So, make 'tune2fs -U' report an error if stable_inodes is set.
Quoted 7 lines
Quoted 2 lines
We could add a separate stable_uuid feature flag, but it seems unlikely it would be useful enough on its own to warrant another flag.
What about having tune2fs walk the inode table checking for any inodes that have this flag, and only refusing to clear the flag if it finds any? That takes some time on very large filesystems, but since inode table reading is linear it is reasonable on most filesystems.
I assume you meant to make this comment on patch 2, "tune2fs: prevent stable_inodes feature from being cleared"?
It's a good suggestion, but it also applies equally to the encrypt, verity, extents, and ea_inode features. Currently tune2fs can't clear any of these, since any inode might be using them.
Note that it would actually be slightly harder to implement your suggestion for stable_inodes than those four existing features, since clearing stable_inodes would require reading xattrs rather than just the inode flags.
Quoted 5 lines
So if I have time, I can certainly look into allowing tune2fs to clear the encrypt, verity, extents, stable_inodes, and ea_inode features, by doing an inode table scan to verify that it's safe. IMO it doesn't make sense to hold up this patch on it, though. This patch just makes stable_inodes work like other ext4 features.

Quoted 8 lines

Sure, I'm OK with this patch, since it avoids accidental breakage.
One question though - for the data checksums it uses s_checksum_seed to generate checksums, rather than directly using the UUID itself, so that it *is* possible to change the filesystem UUID after metadata_csum is in use, without the need to rewrite all of the checksums in the filesystem. Could the same be done for stable_inode?

We could have used s_encrypt_pw_salt, but from a cryptographic perspective I feel a bit safer using the UUID. ext4 metadata checksums are non-cryptographic and for integrity-only, so it's not disastrous if multiple filesystems share the same s_checksum_seed. So EXT4_FEATURE_INCOMPAT_CSUM_SEED makes sense as a usability improvement for people doing things with filesystem cloning.

The new inode-number based encryption is a bit different since it may (depending on how userspace chooses keys) depend on the per-filesystem ID for cryptographic purposes. So it can be much more important that these IDs are really unique.

On this basis, the UUID seems like a better choice since people doing things with filesystem cloning are more likely to remember to set up the UUIDs as unique, vs. some "second UUID" that's more hidden and would be forgotten about.

Using s_encrypt_pw_salt would also have been a bit more complex, as we'd have had to add fscrypt_operations to retrieve it rather than just using s_uuid -- remembering to generate it if unset (mke2fs doesn't set it). We'd also have wanted to rename it to something else like s_encrypt_uuid to avoid confusion as it would no longer be just a password salt.

Anyway, we couldn't really change this now even if we wanted to, since IV_INO_LBLK_64 encryption policies were already released in v5.5.

- Eric

Andreas Dilger

2020-04-10 11:54 UTC #6 lore raw

Re: [PATCH 1/4] tune2fs: prevent changing UUID of fs with stable_inodes feature

Quoted 15 lines · Eric Biggers

Quoted 6 lines · Andreas Dilger
One question though - for the data checksums it uses s_checksum_seed to generate checksums, rather than directly using the UUID itself, so that it *is* possible to change the filesystem UUID after metadata_csum is in use, without the need to rewrite all of the checksums in the filesystem. Could the same be done for stable_inode?
We could have used s_encrypt_pw_salt, but from a cryptographic perspective I feel a bit safer using the UUID. ext4 metadata checksums are non-cryptographic and for integrity-only, so it's not disastrous if multiple filesystems share the same s_checksum_seed. So EXT4_FEATURE_INCOMPAT_CSUM_SEED makes sense as a usability improvement for people doing things with filesystem cloning.

Quoted 7 lines

The new inode-number based encryption is a bit different since it may (depending on how userspace chooses keys) depend on the per-filesystem ID for cryptographic purposes. So it can be much more important that these IDs are really unique.
On this basis, the UUID seems like a better choice since people doing things with filesystem cloning are more likely to remember to set up the UUIDs as unique, vs. some "second UUID" that's more hidden and would be forgotten about.

Actually, I think the opposite is true here. To avoid usability problems, users *have* to change the UUID of a cloned/snapshot filesystem to avoid problems with mount-by-UUID (e.g. either filesystem may be mounted randomly on each boot, depending on the device enumeration order). However, if they try to change the UUID, that would immediately break all of the encrypted files in the filesystem, so that means with the stable_inode feature either:
- a snapshot/clone of a filesystem may subtly break your system, or
- you can't keep a snapshot/clone of such a filesystem on the same node

Quoted 8 lines

Using s_encrypt_pw_salt would also have been a bit more complex, as we'd have had to add fscrypt_operations to retrieve it rather than just using s_uuid -- remembering to generate it if unset (mke2fs doesn't set it). We'd also have wanted to rename it to something else like s_encrypt_uuid to avoid confusion as it would no longer be just a password salt.
Anyway, we couldn't really change this now even if we wanted to, since IV_INO_LBLK_64 encryption policies were already released in v5.5.

I'm not sure I buy these arguments... We changed handling of metadata_csum after the fact, by checking at mount if s_checksum_seed is initialized, otherwise hashing s_uuid and storing if it is zero. Storing s_checksum_seed proactively in the kernel and e2fsck allows users to change s_uuid if they have a new enough kernel without noticing that the checksums were originally based on s_uuid rather than the hash of it in s_checksum_seed.

I'm not sure of the details of whether s_encrypt_pw_salt is used in the IV_INO_LBLK_64 case or not (since it uses inode/block number as the salt?), but I see that the code is already initializing s_encrypt_pw_salt in the kernel if unset, so that is not hard to do. It could just make a copy from s_uuid rather than generating a new UUID for s_encrypt_pw_salt, or for new filesystems it can generate a unique s_encrypt_pw_salt and only use that?

Storing a feature flag to indicate whether s_uuid or s_encrypt_pw_salt is used for the IV_INO_LBLK_64 case seems pretty straight forward? Maybe any filesystems that are using IV_INO_LBLK_64 with s_uuid can't change the UUID, but a few bits and lines of code could allow any new filesystem to do so? If you consider that 5.5 has been out for a few months, there aren't going to be a lot of users of that approach, vs. the next 10 years or more.

In the end, you are the guy who has to deal with issues here, so I leave it to you. I just think it is a problem waiting to happen, and preventing the users from shooting themselves in the foot with tune2fs doesn't mean that they won't have significant problems later that could easily be solved now.

Cheers, Andreas

Theodore Y. Ts'o

maintainer

2020-04-10 15:06 UTC #7 lore raw

Re: [PATCH 1/4] tune2fs: prevent changing UUID of fs with stable_inodes feature

Quoted 9 lines · Andreas Dilger

Actually, I think the opposite is true here. To avoid usability problems, users *have* to change the UUID of a cloned/snapshot filesystem to avoid problems with mount-by-UUID (e.g. either filesystem may be mounted randomly on each boot, depending on the device enumeration order). However, if they try to change the UUID, that would immediately break all of the encrypted files in the filesystem, so that means with the stable_inode feature either:
- a snapshot/clone of a filesystem may subtly break your system, or
- you can't keep a snapshot/clone of such a filesystem on the same node

I don't think there is any reason why we would use IV_INO_LBLK_64 mode on anything other than tablet/mobile devices using the latest UFS or eMMC standards which support in-line crypto engines (ICE). I'm not aware of any cloud VM's, private or public, which supports ICE. And even if they did, hopefully they would use something more sane than the UFS/eMMC spec, which only supports 64 bits of IV per I/O request, and only support a small number of keys that can be loaded into the hardware. (This is what you get when you are optimizing Bill of Materials costs down to a tenth of a cent; a million devices here, retail store profit margins there, and before you know it you're talking real money...)

Furthermore, on an modern x86_64, you can do AES encryption at less than a cycle per CPU clock cycle, and in cloud VM's, battery life is not a concern, so there really isn't any reason to use or implement ICE, except maybe as a testing vehicle for fscrypt (e.g., someone wanting to implement UFS 2.1 in qemu to make it easier to test the Linux kernel's ICE support).

- Ted

Eric Biggers

author maintainer

2020-04-10 16:30 UTC #8 lore raw

Re: [PATCH 1/4] tune2fs: prevent changing UUID of fs with stable_inodes feature

In reply to Andreas Dilger

Quoted 24 lines · Andreas Dilger

Quoted 15 lines · Eric Biggers
Quoted 6 lines · Andreas Dilger
One question though - for the data checksums it uses s_checksum_seed to generate checksums, rather than directly using the UUID itself, so that it *is* possible to change the filesystem UUID after metadata_csum is in use, without the need to rewrite all of the checksums in the filesystem. Could the same be done for stable_inode?
We could have used s_encrypt_pw_salt, but from a cryptographic perspective I feel a bit safer using the UUID. ext4 metadata checksums are non-cryptographic and for integrity-only, so it's not disastrous if multiple filesystems share the same s_checksum_seed. So EXT4_FEATURE_INCOMPAT_CSUM_SEED makes sense as a usability improvement for people doing things with filesystem cloning.
Quoted 7 lines
The new inode-number based encryption is a bit different since it may (depending on how userspace chooses keys) depend on the per-filesystem ID for cryptographic purposes. So it can be much more important that these IDs are really unique.
On this basis, the UUID seems like a better choice since people doing things with filesystem cloning are more likely to remember to set up the UUIDs as unique, vs. some "second UUID" that's more hidden and would be forgotten about.

Quoted 8 lines

Actually, I think the opposite is true here. To avoid usability problems, users *have* to change the UUID of a cloned/snapshot filesystem to avoid problems with mount-by-UUID (e.g. either filesystem may be mounted randomly on each boot, depending on the device enumeration order). However, if they try to change the UUID, that would immediately break all of the encrypted files in the filesystem, so that means with the stable_inode feature either:
- a snapshot/clone of a filesystem may subtly break your system, or
- you can't keep a snapshot/clone of such a filesystem on the same node

My concern is about security, not usability.

If the filesystem IDs used to derive keys for inode-number based encryption aren't unique, then ciphertext may be repeated across files. Users wouldn't notice this since it would be a silent bug, but it would be a cryptographic vulnerability. Systems need to be designed in such a way that silent cryptographic vulnerabilities can't occur, or at least are less likely.

Using the actual UUID rather than a hidden second field encourages people to keep the IDs unique and is simpler.

The existence of s_encrypt_pw_salt does provide some precedent to use a hidden second field, but not much since that's intended to be used with per-file keys. With inode-number based encryption, filesystem ID reuse is a greater concern.

One could validly argue that this is "just a theoretical issue" at the moment, due to the limited systems on which inode-number based encryption would actually be used (as Ted and I have described). But the usability concerns are likewise theoretical at the moment, for the same reason.

Quoted 31 lines

Quoted 9 lines
Using s_encrypt_pw_salt would also have been a bit more complex, as we'd have had to add fscrypt_operations to retrieve it rather than just using s_uuid -- remembering to generate it if unset (mke2fs doesn't set it). We'd also have wanted to rename it to something else like s_encrypt_uuid to avoid confusion as it would no longer be just a password salt.
Anyway, we couldn't really change this now even if we wanted to, since IV_INO_LBLK_64 encryption policies were already released in v5.5.
I'm not sure I buy these arguments... We changed handling of metadata_csum after the fact, by checking at mount if s_checksum_seed is initialized, otherwise hashing s_uuid and storing if it is zero. Storing s_checksum_seed proactively in the kernel and e2fsck allows users to change s_uuid if they have a new enough kernel without noticing that the checksums were originally based on s_uuid rather than the hash of it in s_checksum_seed.
I'm not sure of the details of whether s_encrypt_pw_salt is used in the IV_INO_LBLK_64 case or not (since it uses inode/block number as the salt?), but I see that the code is already initializing s_encrypt_pw_salt in the kernel if unset, so that is not hard to do. It could just make a copy from s_uuid rather than generating a new UUID for s_encrypt_pw_salt, or for new filesystems it can generate a unique s_encrypt_pw_salt and only use that?
Storing a feature flag to indicate whether s_uuid or s_encrypt_pw_salt is used for the IV_INO_LBLK_64 case seems pretty straight forward? Maybe any filesystems that are using IV_INO_LBLK_64 with s_uuid can't change the UUID, but a few bits and lines of code could allow any new filesystem to do so? If you consider that 5.5 has been out for a few months, there aren't going to be a lot of users of that approach, vs. the next 10 years or more.

Quoted 5 lines

In the end, you are the guy who has to deal with issues here, so I leave it to you. I just think it is a problem waiting to happen, and preventing the users from shooting themselves in the foot with tune2fs doesn't mean that they won't have significant problems later that could easily be solved now.

Sure, it wouldn't be *that* hard to add support for using s_encrypt_pw_salt using a separate filesystem feature flag. And it could be done after the fact. My points are just that it would add *some* extra complexity, we already implemented another approach that is fine for the users who would actually use it, and the approach we implemented is more cryptographically robust so switching to the other way wouldn't necessarily be an improvement.

- Eric

Eric Biggers

author maintainer

2020-04-01 20:35 UTC #9 lore raw

PATCH 2/4 tune2fs: prevent stable_inodes feature from being cleared

In reply to Eric Biggers

From: Eric Biggers <[email protected]>

Similar to encrypt and verity, once the stable_inodes feature has been enabled there may be files anywhere on the filesystem that require this feature. Therefore, in general it's unsafe to allow clearing it. Don't allow tune2fs to do so. Like encrypt and verity, it can still be cleared with debugfs if someone really knows what they're doing.

Signed-off-by Eric Biggers <[email protected]>

---
 misc/tune2fs.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

misc/tune2fs.c +1 -2

index ca06c98b..81f90cbf 100644
@@ -181,8 +181,7 @@ static __u32 clear_ok_features[3] = {
 	EXT3_FEATURE_COMPAT_HAS_JOURNAL |
 		EXT2_FEATURE_COMPAT_RESIZE_INODE |
 		EXT2_FEATURE_COMPAT_DIR_INDEX |
-		EXT4_FEATURE_COMPAT_FAST_COMMIT |
-		EXT4_FEATURE_COMPAT_STABLE_INODES,
+		EXT4_FEATURE_COMPAT_FAST_COMMIT,
 	/* Incompat */
 	EXT2_FEATURE_INCOMPAT_FILETYPE |
 		EXT4_FEATURE_INCOMPAT_FLEX_BG |

Signature · 1 line

2.26.0.rc2.310.g2932bb562d-goog

Eric Biggers

author maintainer

2020-04-01 20:35 UTC #10 lore raw

PATCH 3/4 ext4.5: document the stable_inodes feature

In reply to Eric Biggers

From: Eric Biggers <[email protected]>

Signed-off-by Eric Biggers <[email protected]>

---
 misc/ext4.5.in | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

misc/ext4.5.in +16 -0

index 1db61a5f..90bc4f88 100644
@@ -299,6 +299,20 @@ feature is essentially a more extreme version of sparse_super and is
 designed to allow a much larger percentage of the disk to have
 contiguous blocks available for data files.
 .TP
+.B stable_inodes
+.br
+Marks the filesystem's inode numbers and UUID as stable.
+.BR resize2fs (8)
+will not allow shrinking a filesystem with this feature, nor
+will
+.BR tune2fs (8)
+allow changing its UUID.  This feature allows the use of specialized encryption
+settings that make use of the inode numbers and UUID.  Note that the
+.B encrypt
+feature still needs to be enabled separately.
+.B stable_inodes
+is a "compat" feature, so old kernels will allow it.
+.TP
 .B uninit_bg
 .br
 This ext4 file system feature indicates that the block group descriptors

@@ -788,6 +802,8 @@ ext4, 4.13
 ext4, 5.2
 .IP "\fBverity\fR" 2i
 ext4, 5.4
+.IP "\fBstable_inodes\fR" 2i
+ext4, 5.5
 .SH SEE ALSO
 .BR mke2fs (8),
 .BR mke2fs.conf (5),

Signature · 1 line

2.26.0.rc2.310.g2932bb562d-goog

Eric Biggers

author maintainer

2020-04-01 20:35 UTC #11 lore raw

PATCH 4/4 tune2fs.8: document the stable_inodes feature

In reply to Eric Biggers

From: Eric Biggers <[email protected]>

Signed-off-by Eric Biggers <[email protected]>

---
 misc/tune2fs.8.in | 7 +++++++
 1 file changed, 7 insertions(+)

misc/tune2fs.8.in +7 -0

index 3cf1f5ed..582d1da5 100644
@@ -630,6 +630,13 @@ Limit the number of backup superblocks to save space on large filesystems.
 .B Tune2fs
 currently only supports setting this filesystem feature.
 .TP
+.B stable_inodes
+Prevent the filesystem from being shrunk or having its UUID changed, in order to
+allow the use of specialized encryption settings that make use of the inode
+numbers and UUID.
+.B Tune2fs
+currently only supports setting this filesystem feature.
+.TP
 .B uninit_bg
 Allow the kernel to initialize bitmaps and inode tables lazily, and to
 keep a high watermark for the unused inodes in a filesystem, to reduce

Signature · 1 line

2.26.0.rc2.310.g2932bb562d-goog

Andreas Dilger

Reviewed-by on v1 4/4

2020-04-02 02:12 UTC #12 lore raw

Re: [PATCH 4/4] tune2fs.8: document the stable_inodes feature

Quoted 4 lines · Eric Biggers

From: Eric Biggers <[email protected]>
Signed-off-by Eric Biggers <[email protected]>

IMHO, it would be better if the updates to the man pages were in the same patch as the patch to misc/tune2fs.c.

That said, it's better than *not* getting an update to the man page, so:

Reviewed-by Andreas Dilger <[email protected]>

Quoted 19 lines

---
misc/tune2fs.8.in | 7 +++++++

1 file changed, 7 insertions(+)

misc/tune2fs.8.in +0 -0

index 3cf1f5ed..582d1da5 100644
@@ -630,6 +630,13 @@ Limit the number of backup superblocks to save space on large filesystems.

.B Tune2fs
currently only supports setting this filesystem feature. .TP
+.B stable_inodes

misc/tune2fs.8.in +6 -0

+Prevent the filesystem from being shrunk or having its UUID changed, in order to
+allow the use of specialized encryption settings that make use of the inode
+numbers and UUID.
+.B Tune2fs
+currently only supports setting this filesystem feature.
+.TP

Quoted 6 lines

.B uninit_bg
Allow the kernel to initialize bitmaps and inode tables lazily, and to keep a high watermark for the unused inodes in a filesystem, to reduce --
2.26.0.rc2.310.g2932bb562d-goog

Cheers, Andreas

Eric Biggers

author maintainer

2020-04-07 05:10 UTC #13 lore raw

Re: [PATCH 4/4] tune2fs.8: document the stable_inodes feature

Quoted 4 lines · Andreas Dilger

Quoted 3 lines · Eric Biggers
From: Eric Biggers <[email protected]>

Quoted 9 lines

Quoted 1 line
Signed-off-by Eric Biggers <[email protected]>
IMHO, it would be better if the updates to the man pages were in the same patch as the patch to misc/tune2fs.c.
That said, it's better than *not* getting an update to the man page, so:
Reviewed-by Andreas Dilger <[email protected]>

Well, I should have included a man page update when adding '-O stable_inodes' originally several months ago. But now it's just being updated, and it makes more sense to have separate patches for fixes and new documentation.

- Eric

Theodore Y. Ts'o

maintainer

2020-04-10 15:24 UTC #14 lore raw

In reply to Eric Biggers

Quoted 6 lines · Eric Biggers

Fix tune2fs to not allow cases where IV_INO_LBLK_64-encrypted files (which can exist if the stable_inodes feature is set) could be broken:
- Changing the filesystem's UUID
- Clearing the stable_inodes feature

Quoted 7 lines

Also document the stable_inodes feature in the appropriate places.
Eric Biggers (4):
tune2fs: prevent changing UUID of fs with stable_inodes feature
tune2fs: prevent stable_inodes feature from being cleared ext4.5: document the stable_inodes feature
tune2fs.8: document the stable_inodes feature

Thanks, I've applied this patch series.

- Ted

Eric Biggers

author maintainer

2020-05-07 18:18 UTC #15 lore raw

Quoted 9 lines · Theodore Y. Ts'o

Quoted 8 lines · Eric Biggers
Fix tune2fs to not allow cases where IV_INO_LBLK_64-encrypted files (which can exist if the stable_inodes feature is set) could be broken:
- Changing the filesystem's UUID
- Clearing the stable_inodes feature
Also document the stable_inodes feature in the appropriate places.

Quoted 8 lines

Quoted 5 lines
Eric Biggers (4):
tune2fs: prevent changing UUID of fs with stable_inodes feature
tune2fs: prevent stable_inodes feature from being cleared ext4.5: document the stable_inodes feature
tune2fs.8: document the stable_inodes feature
Thanks, I've applied this patch series.

Ted, I still don't see this in git. Are you planning to push it out?

- Eric

Eric Biggers

author maintainer

2020-06-15 22:22 UTC #16 lore raw

Quoted 16 lines · Eric Biggers

Quoted 15 lines · Theodore Y. Ts'o
Quoted 13 lines · Eric Biggers
Fix tune2fs to not allow cases where IV_INO_LBLK_64-encrypted files (which can exist if the stable_inodes feature is set) could be broken:
- Changing the filesystem's UUID
- Clearing the stable_inodes feature
Also document the stable_inodes feature in the appropriate places.
Eric Biggers (4):
tune2fs: prevent changing UUID of fs with stable_inodes feature
tune2fs: prevent stable_inodes feature from being cleared ext4.5: document the stable_inodes feature
tune2fs.8: document the stable_inodes feature

Quoted 5 lines

Quoted 2 lines
Thanks, I've applied this patch series.
Ted, I still don't see this in git. Are you planning to push it out?

Ping?

Eric Biggers

author maintainer

2020-07-27 16:45 UTC #17 lore raw

Quoted 17 lines · Eric Biggers

Quoted 16 lines · Eric Biggers
Quoted 15 lines · Theodore Y. Ts'o
Quoted 13 lines · Eric Biggers
Fix tune2fs to not allow cases where IV_INO_LBLK_64-encrypted files (which can exist if the stable_inodes feature is set) could be broken:
- Changing the filesystem's UUID
- Clearing the stable_inodes feature
Also document the stable_inodes feature in the appropriate places.
Eric Biggers (4):
tune2fs: prevent changing UUID of fs with stable_inodes feature
tune2fs: prevent stable_inodes feature from being cleared ext4.5: document the stable_inodes feature
tune2fs.8: document the stable_inodes feature

Quoted 4 lines

Quoted 4 lines
Quoted 2 lines
Thanks, I've applied this patch series.
Ted, I still don't see this in git. Are you planning to push it out?

Ping?

Eric Biggers

author maintainer

2020-09-01 16:20 UTC #18 lore raw

Quoted 18 lines · Eric Biggers

Quoted 17 lines · Eric Biggers
Quoted 16 lines · Eric Biggers
Quoted 15 lines · Theodore Y. Ts'o
Quoted 13 lines · Eric Biggers
Fix tune2fs to not allow cases where IV_INO_LBLK_64-encrypted files (which can exist if the stable_inodes feature is set) could be broken:
- Changing the filesystem's UUID
- Clearing the stable_inodes feature
Also document the stable_inodes feature in the appropriate places.
Eric Biggers (4):
tune2fs: prevent changing UUID of fs with stable_inodes feature
tune2fs: prevent stable_inodes feature from being cleared ext4.5: document the stable_inodes feature
tune2fs.8: document the stable_inodes feature

Quoted 6 lines

Quoted 4 lines
Quoted 4 lines
Quoted 2 lines
Thanks, I've applied this patch series.
Ted, I still don't see this in git. Are you planning to push it out?
Ping?

Ping.

Eric Biggers

author maintainer

2020-09-21 22:41 UTC #19 lore raw

Quoted 19 lines · Eric Biggers

Quoted 18 lines · Eric Biggers
Quoted 17 lines · Eric Biggers
Quoted 16 lines · Eric Biggers
Quoted 15 lines · Theodore Y. Ts'o
Quoted 13 lines · Eric Biggers
Fix tune2fs to not allow cases where IV_INO_LBLK_64-encrypted files (which can exist if the stable_inodes feature is set) could be broken:
- Changing the filesystem's UUID
- Clearing the stable_inodes feature
Also document the stable_inodes feature in the appropriate places.
Eric Biggers (4):
tune2fs: prevent changing UUID of fs with stable_inodes feature
tune2fs: prevent stable_inodes feature from being cleared ext4.5: document the stable_inodes feature
tune2fs.8: document the stable_inodes feature

Quoted 8 lines

Quoted 6 lines
Quoted 4 lines
Quoted 4 lines
Quoted 2 lines
Thanks, I've applied this patch series.
Ted, I still don't see this in git. Are you planning to push it out?
Ping?
Ping.

Ping.