[PATCH V5] ext4: check hash version and filesystem casefolded consistent

[PATCH V5] ext4: check hash version and filesystem casefolded consistent

[Lizhi Xu]

When mounting the ext4 filesystem, if the hash version and casefolded are not
consistent, exit the mounting.

Reported-by: syzbot+340581ba9dceb7e06fb3@syzkaller.appspotmail.com
Signed-off-by: Lizhi Xu <lizhi.xu@windriver.com>
---
 fs/ext4/super.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index c682fb927b64..0ad326504c50 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -5262,6 +5262,11 @@ static int __ext4_fill_super(struct fs_context *fc, struct super_block *sb)
 		goto failed_mount;
 
 	ext4_hash_info_init(sb);
+	if (es->s_def_hash_version == DX_HASH_SIPHASH && 
+	    !ext4_has_feature_casefold(sb)) {
+		err = -EINVAL;
+		goto failed_mount;
+	}
 
 	err = ext4_handle_clustersize(sb);
 	if (err)
-- 
2.43.0

Re: [PATCH V5] ext4: check hash version and filesystem casefolded consistent

[Gabriel Krisman Bertazi]

Lizhi Xu <lizhi.xu@windriver.com> writes:

> When mounting the ext4 filesystem, if the hash version and casefolded are not
> consistent, exit the mounting.
>
> Reported-by: syzbot+340581ba9dceb7e06fb3@syzkaller.appspotmail.com
> Signed-off-by: Lizhi Xu <lizhi.xu@windriver.com>
> ---
>  fs/ext4/super.c | 5 +++++
>  1 file changed, 5 insertions(+)
>
> diff --git a/fs/ext4/super.c b/fs/ext4/super.c
> index c682fb927b64..0ad326504c50 100644
> --- a/fs/ext4/super.c
> +++ b/fs/ext4/super.c
> @@ -5262,6 +5262,11 @@ static int __ext4_fill_super(struct fs_context *fc, struct super_block *sb)
>  		goto failed_mount;
>  
>  	ext4_hash_info_init(sb);
> +	if (es->s_def_hash_version == DX_HASH_SIPHASH && 
> +	    !ext4_has_feature_casefold(sb)) {

Can we ever have DX_HASH_SIPHASH set up in the super block?  I thought
it was used solely for directories where ext4_hash_in_dirent(inode) is
true.

If this is only for the case of a superblock corruption, perhaps we
should always reject the mount, whether casefold is enabled or not?

-- 
Gabriel Krisman Bertazi

Re: [PATCH V5] ext4: check hash version and filesystem casefolded consistent

[Lizhi Xu]

On Mon, 03 Jun 2024 10:50:51 -0400, Gabriel Krisman Bertazi wrote:
> > When mounting the ext4 filesystem, if the hash version and casefolded are not
> > consistent, exit the mounting.
> >
> > Reported-by: syzbot+340581ba9dceb7e06fb3@syzkaller.appspotmail.com
> > Signed-off-by: Lizhi Xu <lizhi.xu@windriver.com>
> > ---
> >  fs/ext4/super.c | 5 +++++
> >  1 file changed, 5 insertions(+)
> >
> > diff --git a/fs/ext4/super.c b/fs/ext4/super.c
> > index c682fb927b64..0ad326504c50 100644
> > --- a/fs/ext4/super.c
> > +++ b/fs/ext4/super.c
> > @@ -5262,6 +5262,11 @@ static int __ext4_fill_super(struct fs_context *fc, struct super_block *sb)
> >  		goto failed_mount;
> >  
> >  	ext4_hash_info_init(sb);
> > +	if (es->s_def_hash_version == DX_HASH_SIPHASH && 
> > +	    !ext4_has_feature_casefold(sb)) {
> 
> Can we ever have DX_HASH_SIPHASH set up in the super block?  I thought
> it was used solely for directories where ext4_hash_in_dirent(inode) is
> true.
The value of s'def_hash_version is obtained by reading the super block from the
buffer cache of the block device in ext4_load_super().
> 
> If this is only for the case of a superblock corruption, perhaps we
> should always reject the mount, whether casefold is enabled or not?
Based on the existing information, it cannot be confirmed whether the superblock
is corrupt, but one thing is clear: if the default hash version of the superblock
is set to DX_HASH_SIPHASH, but the casefold feature is not set at the same time,
it is definitely an error.

Lizhi

Re: [PATCH V5] ext4: check hash version and filesystem casefolded consistent

[Gabriel Krisman Bertazi]

Lizhi Xu <lizhi.xu@windriver.com> writes:

> On Mon, 03 Jun 2024 10:50:51 -0400, Gabriel Krisman Bertazi wrote:
>> > When mounting the ext4 filesystem, if the hash version and casefolded are not
>> > consistent, exit the mounting.
>> >
>> > Reported-by: syzbot+340581ba9dceb7e06fb3@syzkaller.appspotmail.com
>> > Signed-off-by: Lizhi Xu <lizhi.xu@windriver.com>
>> > ---
>> >  fs/ext4/super.c | 5 +++++
>> >  1 file changed, 5 insertions(+)
>> >
>> > diff --git a/fs/ext4/super.c b/fs/ext4/super.c
>> > index c682fb927b64..0ad326504c50 100644
>> > --- a/fs/ext4/super.c
>> > +++ b/fs/ext4/super.c
>> > @@ -5262,6 +5262,11 @@ static int __ext4_fill_super(struct fs_context *fc, struct super_block *sb)
>> >  		goto failed_mount;
>> >  
>> >  	ext4_hash_info_init(sb);
>> > +	if (es->s_def_hash_version == DX_HASH_SIPHASH && 
>> > +	    !ext4_has_feature_casefold(sb)) {
>> 
>> Can we ever have DX_HASH_SIPHASH set up in the super block?  I thought
>> it was used solely for directories where ext4_hash_in_dirent(inode) is
>> true.
> The value of s'def_hash_version is obtained by reading the super block from the
> buffer cache of the block device in ext4_load_super().

Yes, I know.  My point is whether this check should just be:

if (es->s_def_hash_version == DX_HASH_SIPHASH)
	goto failed_mount;

Since, IIUC, DX_HASH_SIPHASH is done per-directory and not written to
the sb.

>> If this is only for the case of a superblock corruption, perhaps we
>> should always reject the mount, whether casefold is enabled or not?
> Based on the existing information, it cannot be confirmed whether the superblock
> is corrupt, but one thing is clear: if the default hash version of the superblock
> is set to DX_HASH_SIPHASH, but the casefold feature is not set at the same time,
> it is definitely an error.


-- 
Gabriel Krisman Bertazi

Re: [PATCH V5] ext4: check hash version and filesystem casefolded consistent

[Lizhi Xu]

On Tue, 04 Jun 2024 15:06:32 -0400, Gabriel Krisman Bertazi wrote:
> >> > When mounting the ext4 filesystem, if the hash version and casefolded are not
> >> > consistent, exit the mounting.
> >> >
> >> > Reported-by: syzbot+340581ba9dceb7e06fb3@syzkaller.appspotmail.com
> >> > Signed-off-by: Lizhi Xu <lizhi.xu@windriver.com>
> >> > ---
> >> >  fs/ext4/super.c | 5 +++++
> >> >  1 file changed, 5 insertions(+)
> >> >
> >> > diff --git a/fs/ext4/super.c b/fs/ext4/super.c
> >> > index c682fb927b64..0ad326504c50 100644
> >> > --- a/fs/ext4/super.c
> >> > +++ b/fs/ext4/super.c
> >> > @@ -5262,6 +5262,11 @@ static int __ext4_fill_super(struct fs_context *fc, struct super_block *sb)
> >> >  		goto failed_mount;
> >> >  
> >> >  	ext4_hash_info_init(sb);
> >> > +	if (es->s_def_hash_version == DX_HASH_SIPHASH && 
> >> > +	    !ext4_has_feature_casefold(sb)) {
> >> 
> >> Can we ever have DX_HASH_SIPHASH set up in the super block?  I thought
> >> it was used solely for directories where ext4_hash_in_dirent(inode) is
> >> true.
> > The value of s'def_hash_version is obtained by reading the super block from the
> > buffer cache of the block device in ext4_load_super().
> 
> Yes, I know.  My point is whether this check should just be:
Based on the existing information, it cannot be confirmed that it is incorrect
to separately determine the value of s_def_hash_version as DX_HASH_SIPHASH.
Additionally, I have come up with a better solution, and I will issue the next
fixed version in a while.
> 
> if (es->s_def_hash_version == DX_HASH_SIPHASH)
> 	goto failed_mount;
> 
> Since, IIUC, DX_HASH_SIPHASH is done per-directory and not written to
> the sb.
> 
> >> If this is only for the case of a superblock corruption, perhaps we
> >> should always reject the mount, whether casefold is enabled or not?
> > Based on the existing information, it cannot be confirmed whether the superblock
> > is corrupt, but one thing is clear: if the default hash version of the superblock
> > is set to DX_HASH_SIPHASH, but the casefold feature is not set at the same time,
> > it is definitely an error.

Lizhi

[PATCH V6] fs/ext4: Filesystem without casefold feature cannot be mounted with spihash

[Lizhi Xu]

When mounting the ext4 filesystem, if the default hash version is set to 
DX_HASH_SIPHASH but the casefold feature is not set, exit the mounting.

Reported-by: syzbot+340581ba9dceb7e06fb3@syzkaller.appspotmail.com
Signed-off-by: Lizhi Xu <lizhi.xu@windriver.com>
---
 fs/ext4/super.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index c682fb927b64..d0645af3e66e 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -3593,6 +3593,14 @@ int ext4_feature_set_ok(struct super_block *sb, int readonly)
 			 "mounted without CONFIG_UNICODE");
 		return 0;
 	}
+#else
+	if (EXT4_SB(sb)->s_es->s_def_hash_version == DX_HASH_SIPHASH &&
+	    !ext4_has_feature_casefold(sb)) {
+		ext4_msg(sb, KERN_ERR,
+			 "Filesystem without casefold feature cannot be "
+			 "mounted with spihash");
+		return 0;
+	}
 #endif
 
 	if (readonly)
-- 
2.43.0

Re: [PATCH V6] fs/ext4: Filesystem without casefold feature cannot be mounted with spihash

[Theodore Ts'o]

On Wed, 05 Jun 2024 09:23:35 +0800, Lizhi Xu wrote:
> When mounting the ext4 filesystem, if the default hash version is set to
> DX_HASH_SIPHASH but the casefold feature is not set, exit the mounting.
> 
> 

Applied, thanks!

[1/1] fs/ext4: Filesystem without casefold feature cannot be mounted with spihash
      commit: 985b67cd86392310d9e9326de941c22fc9340eec

Best regards,
-- 
Theodore Ts'o <tytso@mit.edu>

[PATCH] ext4: Fix error message when rejecting the default hash

[Gabriel Krisman Bertazi]

"Theodore Ts'o" <tytso@mit.edu> writes:

> On Wed, 05 Jun 2024 09:23:35 +0800, Lizhi Xu wrote:
>> When mounting the ext4 filesystem, if the default hash version is set to
>> DX_HASH_SIPHASH but the casefold feature is not set, exit the mounting.
>> 
>> 
>
> Applied, thanks!
>
> [1/1] fs/ext4: Filesystem without casefold feature cannot be mounted with spihash
>       commit: 985b67cd86392310d9e9326de941c22fc9340eec

Ted,

Since you took the above, can you please consider the following fixup?
I had pointed we shouldn't have siphash as the sb default hash at all:

based on your dev branch.

>8
Subject: [PATCH] ext4: Fix error message when rejecting the default hash

Commit 985b67cd8639 ("ext4: filesystems without casefold feature cannot
be mounted with siphash") properly rejects volumes where
s_def_hash_version is set to DX_HASH_SIPHASH, but the check and the
error message should not look into casefold setup - a filesystem should
never have DX_HASH_SIPHASH as the default hash.  Fix it and, since we
are there, move the check to ext4_hash_info_init.

Fixes:985b67cd8639 ("ext4: filesystems without casefold feature cannot
be mounted with siphash")
Signed-off-by: Gabriel Krisman Bertazi <krisman@suse.de>
---
 fs/ext4/ext4.h  |  1 +
 fs/ext4/super.c | 27 +++++++++++++++++----------
 2 files changed, 18 insertions(+), 10 deletions(-)

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 5845e4aa091a..4120f24880cb 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -2462,6 +2462,7 @@ static inline __le16 ext4_rec_len_to_disk(unsigned len, unsigned blocksize)
 #define DX_HASH_HALF_MD4_UNSIGNED	4
 #define DX_HASH_TEA_UNSIGNED		5
 #define DX_HASH_SIPHASH			6
+#define DX_HASH_LAST 			DX_HASH_SIPHASH
 
 static inline u32 ext4_chksum(struct ext4_sb_info *sbi, u32 crc,
 			      const void *address, unsigned int length)
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 25cd0d662e31..c6a34ad07ecc 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -3582,13 +3582,6 @@ int ext4_feature_set_ok(struct super_block *sb, int readonly)
 			 "mounted without CONFIG_UNICODE");
 		return 0;
 	}
-	if (EXT4_SB(sb)->s_es->s_def_hash_version == DX_HASH_SIPHASH &&
-	    !ext4_has_feature_casefold(sb)) {
-		ext4_msg(sb, KERN_ERR,
-			 "Filesystem without casefold feature cannot be "
-			 "mounted with siphash");
-		return 0;
-	}
 
 	if (readonly)
 		return 1;
@@ -5094,16 +5087,27 @@ static int ext4_load_super(struct super_block *sb, ext4_fsblk_t *lsb,
 	return ret;
 }
 
-static void ext4_hash_info_init(struct super_block *sb)
+static int ext4_hash_info_init(struct super_block *sb)
 {
 	struct ext4_sb_info *sbi = EXT4_SB(sb);
 	struct ext4_super_block *es = sbi->s_es;
 	unsigned int i;
 
+	sbi->s_def_hash_version = es->s_def_hash_version;
+
+	if (sbi->s_def_hash_version > DX_HASH_LAST) {
+		ext4_msg(sb, KERN_ERR,
+			 "Invalid default hash set in the superblock");
+		return -EINVAL;
+	} else if (sbi->s_def_hash_version == DX_HASH_SIPHASH) {
+		ext4_msg(sb, KERN_ERR,
+			 "SIPHASH is not a valid default hash value");
+		return -EINVAL;
+	}
+
 	for (i = 0; i < 4; i++)
 		sbi->s_hash_seed[i] = le32_to_cpu(es->s_hash_seed[i]);
 
-	sbi->s_def_hash_version = es->s_def_hash_version;
 	if (ext4_has_feature_dir_index(sb)) {
 		i = le32_to_cpu(es->s_flags);
 		if (i & EXT2_FLAGS_UNSIGNED_HASH)
@@ -5121,6 +5125,7 @@ static void ext4_hash_info_init(struct super_block *sb)
 #endif
 		}
 	}
+	return 0;
 }
 
 static int ext4_block_group_meta_init(struct super_block *sb, int silent)
@@ -5256,7 +5261,9 @@ static int __ext4_fill_super(struct fs_context *fc, struct super_block *sb)
 	if (err)
 		goto failed_mount;
 
-	ext4_hash_info_init(sb);
+	err = ext4_hash_info_init(sb);
+	if (err)
+		goto failed_mount;
 
 	err = ext4_handle_clustersize(sb);
 	if (err)
-- 
2.46.0

Re: [PATCH] ext4: Fix error message when rejecting the default hash

[Theodore Ts'o]

On Tue, 27 Aug 2024 16:16:36 -0400, Gabriel Krisman Bertazi wrote:
> "Theodore Ts'o" <tytso@mit.edu> writes:
> 
> > On Wed, 05 Jun 2024 09:23:35 +0800, Lizhi Xu wrote:
> >> When mounting the ext4 filesystem, if the default hash version is set to
> >> DX_HASH_SIPHASH but the casefold feature is not set, exit the mounting.
> >>
> >>
> >
> > Applied, thanks!
> >
> > [1/1] fs/ext4: Filesystem without casefold feature cannot be mounted with spihash
> >       commit: 985b67cd86392310d9e9326de941c22fc9340eec
> 
> [...]

Applied, thanks!

[1/1] ext4: Fix error message when rejecting the default hash
      commit: a2187431c395cdfbf144e3536f25468c64fc7cfa

Best regards,
-- 
Theodore Ts'o <tytso@mit.edu>

Re: [PATCH V5] ext4: check hash version and filesystem casefolded consistent

[Eric Biggers]

On Tue, Jun 04, 2024 at 03:06:32PM -0400, Gabriel Krisman Bertazi wrote:
> Lizhi Xu <lizhi.xu@windriver.com> writes:
> 
> > On Mon, 03 Jun 2024 10:50:51 -0400, Gabriel Krisman Bertazi wrote:
> >> > When mounting the ext4 filesystem, if the hash version and casefolded are not
> >> > consistent, exit the mounting.
> >> >
> >> > Reported-by: syzbot+340581ba9dceb7e06fb3@syzkaller.appspotmail.com
> >> > Signed-off-by: Lizhi Xu <lizhi.xu@windriver.com>
> >> > ---
> >> >  fs/ext4/super.c | 5 +++++
> >> >  1 file changed, 5 insertions(+)
> >> >
> >> > diff --git a/fs/ext4/super.c b/fs/ext4/super.c
> >> > index c682fb927b64..0ad326504c50 100644
> >> > --- a/fs/ext4/super.c
> >> > +++ b/fs/ext4/super.c
> >> > @@ -5262,6 +5262,11 @@ static int __ext4_fill_super(struct fs_context *fc, struct super_block *sb)
> >> >  		goto failed_mount;
> >> >  
> >> >  	ext4_hash_info_init(sb);
> >> > +	if (es->s_def_hash_version == DX_HASH_SIPHASH && 
> >> > +	    !ext4_has_feature_casefold(sb)) {
> >> 
> >> Can we ever have DX_HASH_SIPHASH set up in the super block?  I thought
> >> it was used solely for directories where ext4_hash_in_dirent(inode) is
> >> true.
> > The value of s'def_hash_version is obtained by reading the super block from the
> > buffer cache of the block device in ext4_load_super().
> 
> Yes, I know.  My point is whether this check should just be:
> 
> if (es->s_def_hash_version == DX_HASH_SIPHASH)
> 	goto failed_mount;
> 
> Since, IIUC, DX_HASH_SIPHASH is done per-directory and not written to
> the sb.
> 

That seems right to me.  SipHash can never be the default because it's only used
on directories that are both encrypted and casefolded.

- Eric