Re: [syzbot] possible fix (linux-ntfs3)

[syzbot <syzbot+7a2ba6b7b66340cff225@syzkaller.appspotmail.com>]

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Subject: possible fix (linux-ntfs3)
Author: almaz.alexandrovich@paragon-software.com

Not sure about all indexes on volume must have the same index_block_size.

#syz test: https://github.com/Paragon-Software-Group/linux-ntfs3.git master

diff --git a/fs/ntfs3/index.c b/fs/ntfs3/index.c
index 9089c58a005c..63fbb8ba6e1b 100644
--- a/fs/ntfs3/index.c
+++ b/fs/ntfs3/index.c
@@ -892,7 +892,9 @@ int indx_init(struct ntfs_index *indx, struct ntfs_sb_info *sbi,
 	indx->idx2vbn_bits = __ffs(root->index_block_clst);
 
 	t32 = le32_to_cpu(root->index_block_size);
-	indx->index_bits = blksize_bits(t32);
+	if (t32 != sbi->index_size)
+		goto out;
+	indx->index_bits = sbi->index_bits;
 
 	/* Check index record size. */
 	if (t32 < sbi->cluster_size) {
diff --git a/fs/ntfs3/ntfs_fs.h b/fs/ntfs3/ntfs_fs.h
index 3dd6215316e4..73d72fa8ab65 100644
--- a/fs/ntfs3/ntfs_fs.h
+++ b/fs/ntfs3/ntfs_fs.h
@@ -222,8 +222,9 @@ struct ntfs_sb_info {
 	u32 record_size;
 	u32 index_size;
 
-	u8 cluster_bits;
-	u8 record_bits;
+	u8 cluster_bits; // log2(cluster_size)
+	u8 record_bits; // log2(record_size)
+	u8 index_bits; // log2(index_size)
 
 	u64 maxbytes; // Maximum size for normal files.
 	u64 maxbytes_sparse; // Maximum size for sparse file.
diff --git a/fs/ntfs3/super.c b/fs/ntfs3/super.c
index 128d49512f5d..f96641b80869 100644
--- a/fs/ntfs3/super.c
+++ b/fs/ntfs3/super.c
@@ -993,6 +993,7 @@ static int ntfs_init_from_boot(struct super_block *sb, u32 sector_size,
 			 sbi->index_size);
 		goto out;
 	}
+	sbi->index_bits = blksize_bits(sbi->index_size);
 
 	sbi->volume.size = sectors * boot_sector_size;