ext4: calculate and verify checksums for inode bitmaps

Compute and verify the checksum of the inode bitmap; the checkum is
stored in the block group descriptor.
Signed-off-by: Darrick J. Wong <djwong@us.ibm.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

fs/ext4/bitmap.c

@@ -29,3 +29,42 @@ unsigned int ext4_count_free(struct buffer_head *map, unsigned int numchars)
 
 #endif  /*  EXT4FS_DEBUG  */
 
+int ext4_inode_bitmap_csum_verify(struct super_block *sb, ext4_group_t group,
+				  struct ext4_group_desc *gdp,
+				  struct buffer_head *bh, int sz)
+{
+	__u32 hi;
+	__u32 provided, calculated;
+	struct ext4_sb_info *sbi = EXT4_SB(sb);
+
+	if (!EXT4_HAS_RO_COMPAT_FEATURE(sb,
+					EXT4_FEATURE_RO_COMPAT_METADATA_CSUM))
+		return 1;
+
+	provided = le16_to_cpu(gdp->bg_inode_bitmap_csum_lo);
+	calculated = ext4_chksum(sbi, sbi->s_csum_seed, (__u8 *)bh->b_data, sz);
+	if (sbi->s_desc_size >= EXT4_BG_INODE_BITMAP_CSUM_HI_END) {
+		hi = le16_to_cpu(gdp->bg_inode_bitmap_csum_hi);
+		provided |= (hi << 16);
+	} else
+		calculated &= 0xFFFF;
+
+	return provided == calculated;
+}
+
+void ext4_inode_bitmap_csum_set(struct super_block *sb, ext4_group_t group,
+				struct ext4_group_desc *gdp,
+				struct buffer_head *bh, int sz)
+{
+	__u32 csum;
+	struct ext4_sb_info *sbi = EXT4_SB(sb);
+
+	if (!EXT4_HAS_RO_COMPAT_FEATURE(sb,
+					EXT4_FEATURE_RO_COMPAT_METADATA_CSUM))
+		return;
+
+	csum = ext4_chksum(sbi, sbi->s_csum_seed, (__u8 *)bh->b_data, sz);
+	gdp->bg_inode_bitmap_csum_lo = cpu_to_le16(csum & 0xFFFF);
+	if (sbi->s_desc_size >= EXT4_BG_INODE_BITMAP_CSUM_HI_END)
+		gdp->bg_inode_bitmap_csum_hi = cpu_to_le16(csum >> 16);
+}

fs/ext4/ext4.h

@@ -317,6 +317,13 @@ struct ext4_group_desc
 	__u32   bg_reserved;
 };
 
+#define EXT4_BG_INODE_BITMAP_CSUM_HI_END	\
+	(offsetof(struct ext4_group_desc, bg_inode_bitmap_csum_hi) + \
+	 sizeof(__le16))
+#define EXT4_BG_BLOCK_BITMAP_CSUM_HI_END	\
+	(offsetof(struct ext4_group_desc, bg_block_bitmap_csum_hi) + \
+	 sizeof(__le16))
+
 /*
  * Structure of a flex block group info
  */
@@ -1844,6 +1851,12 @@ struct mmpd_data {
 
 /* bitmap.c */
 extern unsigned int ext4_count_free(struct buffer_head *, unsigned);
+void ext4_inode_bitmap_csum_set(struct super_block *sb, ext4_group_t group,
+				struct ext4_group_desc *gdp,
+				struct buffer_head *bh, int sz);
+int ext4_inode_bitmap_csum_verify(struct super_block *sb, ext4_group_t group,
+				  struct ext4_group_desc *gdp,
+				  struct buffer_head *bh, int sz);
 
 /* balloc.c */
 extern unsigned int ext4_block_group(struct super_block *sb,
@@ -2094,6 +2107,13 @@ extern __le16 ext4_group_desc_csum(struct ext4_sb_info *sbi, __u32 group,
 extern int ext4_group_desc_csum_verify(struct ext4_sb_info *sbi, __u32 group,
 				       struct ext4_group_desc *gdp);
 
+static inline int ext4_has_group_desc_csum(struct super_block *sb)
+{
+	return EXT4_HAS_RO_COMPAT_FEATURE(sb,
+					  EXT4_FEATURE_RO_COMPAT_GDT_CSUM |
+					  EXT4_FEATURE_RO_COMPAT_METADATA_CSUM);
+}
+
 static inline ext4_fsblk_t ext4_blocks_count(struct ext4_super_block *es)
 {
 	return ((ext4_fsblk_t)le32_to_cpu(es->s_blocks_count_hi) << 32) |

fs/ext4/ialloc.c

@@ -82,12 +82,17 @@ static unsigned ext4_init_inode_bitmap(struct super_block *sb,
 		ext4_free_inodes_set(sb, gdp, 0);
 		ext4_itable_unused_set(sb, gdp, 0);
 		memset(bh->b_data, 0xff, sb->s_blocksize);
+		ext4_inode_bitmap_csum_set(sb, block_group, gdp, bh,
+					   EXT4_INODES_PER_GROUP(sb) / 8);
 		return 0;
 	}
 
 	memset(bh->b_data, 0, (EXT4_INODES_PER_GROUP(sb) + 7) / 8);
 	ext4_mark_bitmap_end(EXT4_INODES_PER_GROUP(sb), sb->s_blocksize * 8,
 			bh->b_data);
+	ext4_inode_bitmap_csum_set(sb, block_group, gdp, bh,
+				   EXT4_INODES_PER_GROUP(sb) / 8);
+	gdp->bg_checksum = ext4_group_desc_csum(sbi, block_group, gdp);
 
 	return EXT4_INODES_PER_GROUP(sb);
 }
@@ -128,12 +133,12 @@ ext4_read_inode_bitmap(struct super_block *sb, ext4_group_t block_group)
 		return NULL;
 	}
 	if (bitmap_uptodate(bh))
-		return bh;
+		goto verify;
 
 	lock_buffer(bh);
 	if (bitmap_uptodate(bh)) {
 		unlock_buffer(bh);
-		return bh;
+		goto verify;
 	}
 
 	ext4_lock_group(sb, block_group);
@@ -141,6 +146,7 @@ ext4_read_inode_bitmap(struct super_block *sb, ext4_group_t block_group)
 		ext4_init_inode_bitmap(sb, bh, block_group, desc);
 		set_bitmap_uptodate(bh);
 		set_buffer_uptodate(bh);
+		set_buffer_verified(bh);
 		ext4_unlock_group(sb, block_group);
 		unlock_buffer(bh);
 		return bh;
@@ -154,7 +160,7 @@ ext4_read_inode_bitmap(struct super_block *sb, ext4_group_t block_group)
 		 */
 		set_bitmap_uptodate(bh);
 		unlock_buffer(bh);
-		return bh;
+		goto verify;
 	}
 	/*
 	 * submit the buffer_head for reading
@@ -171,6 +177,20 @@ ext4_read_inode_bitmap(struct super_block *sb, ext4_group_t block_group)
 			   block_group, bitmap_blk);
 		return NULL;
 	}
+
+verify:
+	ext4_lock_group(sb, block_group);
+	if (!buffer_verified(bh) &&
+	    !ext4_inode_bitmap_csum_verify(sb, block_group, desc, bh,
+					   EXT4_INODES_PER_GROUP(sb) / 8)) {
+		ext4_unlock_group(sb, block_group);
+		put_bh(bh);
+		ext4_error(sb, "Corrupt inode bitmap - block_group = %u, "
+			   "inode_bitmap = %llu", block_group, bitmap_blk);
+		return NULL;
+	}
+	ext4_unlock_group(sb, block_group);
+	set_buffer_verified(bh);
 	return bh;
 }
 
@@ -276,6 +296,8 @@ void ext4_free_inode(handle_t *handle, struct inode *inode)
 		ext4_used_dirs_set(sb, gdp, count);
 		percpu_counter_dec(&sbi->s_dirs_counter);
 	}
+	ext4_inode_bitmap_csum_set(sb, block_group, gdp, bitmap_bh,
+				   EXT4_INODES_PER_GROUP(sb) / 8);
 	gdp->bg_checksum = ext4_group_desc_csum(sbi, block_group, gdp);
 	ext4_unlock_group(sb, block_group);
 
@@ -751,7 +773,7 @@ struct inode *ext4_new_inode(handle_t *handle, struct inode *dir, umode_t mode,
 		goto fail;
 
 	/* Update the relevant bg descriptor fields */
-	if (EXT4_HAS_RO_COMPAT_FEATURE(sb, EXT4_FEATURE_RO_COMPAT_GDT_CSUM)) {
+	if (ext4_has_group_desc_csum(sb)) {
 		int free;
 		struct ext4_group_info *grp = ext4_get_group_info(sb, group);
 
@@ -782,7 +804,9 @@ struct inode *ext4_new_inode(handle_t *handle, struct inode *dir, umode_t mode,
 			atomic_inc(&sbi->s_flex_groups[f].used_dirs);
 		}
 	}
-	if (EXT4_HAS_RO_COMPAT_FEATURE(sb, EXT4_FEATURE_RO_COMPAT_GDT_CSUM)) {
+	if (ext4_has_group_desc_csum(sb)) {
+		ext4_inode_bitmap_csum_set(sb, group, gdp, inode_bitmap_bh,
+					   EXT4_INODES_PER_GROUP(sb) / 8);
 		gdp->bg_checksum = ext4_group_desc_csum(sbi, group, gdp);
 		ext4_unlock_group(sb, group);
 	}

fs/ext4/resize.c

@@ -1069,6 +1069,47 @@ static int ext4_add_new_descs(handle_t *handle, struct super_block *sb,
 	return err;
 }
 
+static struct buffer_head *ext4_get_bitmap(struct super_block *sb, __u64 block)
+{
+	struct buffer_head *bh = sb_getblk(sb, block);
+	if (!bh)
+		return NULL;
+
+	if (bitmap_uptodate(bh))
+		return bh;
+
+	lock_buffer(bh);
+	if (bh_submit_read(bh) < 0) {
+		unlock_buffer(bh);
+		brelse(bh);
+		return NULL;
+	}
+	unlock_buffer(bh);
+
+	return bh;
+}
+
+static int ext4_set_bitmap_checksums(struct super_block *sb,
+				     ext4_group_t group,
+				     struct ext4_group_desc *gdp,
+				     struct ext4_new_group_data *group_data)
+{
+	struct buffer_head *bh;
+
+	if (!EXT4_HAS_RO_COMPAT_FEATURE(sb,
+					EXT4_FEATURE_RO_COMPAT_METADATA_CSUM))
+		return 0;
+
+	bh = ext4_get_bitmap(sb, group_data->inode_bitmap);
+	if (!bh)
+		return -EIO;
+	ext4_inode_bitmap_csum_set(sb, group, gdp, bh,
+				   EXT4_INODES_PER_GROUP(sb) / 8);
+	brelse(bh);
+
+	return 0;
+}
+
 /*
  * ext4_setup_new_descs() will set up the group descriptor descriptors of a flex bg
  */
@@ -1101,6 +1142,12 @@ static int ext4_setup_new_descs(handle_t *handle, struct super_block *sb,
 		memset(gdp, 0, EXT4_DESC_SIZE(sb));
 		ext4_block_bitmap_set(sb, gdp, group_data->block_bitmap);
 		ext4_inode_bitmap_set(sb, gdp, group_data->inode_bitmap);
+		err = ext4_set_bitmap_checksums(sb, group, gdp, group_data);
+		if (err) {
+			ext4_std_error(sb, err);
+			break;
+		}
+
 		ext4_inode_table_set(sb, gdp, group_data->inode_table);
 		ext4_free_group_clusters_set(sb, gdp,
 					     EXT4_B2C(sbi, group_data->free_blocks_count));