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

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Message-ID: <87jzg1en6j.fsf_-_@mailhost.krisman.be>
Date: Tue, 27 Aug 2024 16:16:36 -0400
From: Gabriel Krisman Bertazi <krisman@...e.de>
To: "Theodore Ts'o" <tytso@....edu>
Cc: Lizhi Xu <lizhi.xu@...driver.com>,  adilger.kernel@...ger.ca,
  coreteam@...filter.org,  davem@...emloft.net,  ebiggers@...nel.org,
  fw@...len.de,  jaegeuk@...nel.org,  kadlec@...filter.org,
  kuba@...nel.org,  linux-ext4@...r.kernel.org,
  linux-fscrypt@...r.kernel.org,  linux-kernel@...r.kernel.org,
  lkp@...el.com,  llvm@...ts.linux.dev,  netdev@...r.kernel.org,
  netfilter-devel@...r.kernel.org,  oe-kbuild-all@...ts.linux.dev,
  pablo@...filter.org,
  syzbot+340581ba9dceb7e06fb3@...kaller.appspotmail.com,
  syzkaller-bugs@...glegroups.com
Subject: [PATCH] ext4: Fix error message when rejecting the default hash

"Theodore Ts'o" <tytso@....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@...e.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