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Subject[PATCH 08/16] ext4: Calculate and verify checksums for inode bitmaps
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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>
---
fs/ext4/ext4.h | 3 ++-
fs/ext4/ialloc.c | 33 ++++++++++++++++++++++++++++++---
2 files changed, 32 insertions(+), 4 deletions(-)

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index bc7ace1..248cbd2 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -279,7 +279,8 @@ struct ext4_group_desc
__le16 bg_free_inodes_count_hi;/* Free inodes count MSB */
__le16 bg_used_dirs_count_hi; /* Directories count MSB */
__le16 bg_itable_unused_hi; /* Unused inodes count MSB */
- __u32 bg_reserved2[3];
+ __le32 bg_inode_bitmap_csum; /* crc32c(uuid+group+ibitmap) */
+ __u32 bg_reserved2[2];
};

/*
diff --git a/fs/ext4/ialloc.c b/fs/ext4/ialloc.c
index 9c63f27..53faffc 100644
--- a/fs/ext4/ialloc.c
+++ b/fs/ext4/ialloc.c
@@ -82,12 +82,18 @@ 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_bitmap_csum_set(sb, block_group,
+ &gdp->bg_inode_bitmap_csum, bh,
+ (EXT4_INODES_PER_GROUP(sb) + 7) / 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_bitmap_csum_set(sb, block_group, &gdp->bg_inode_bitmap_csum, bh,
+ (EXT4_INODES_PER_GROUP(sb) + 7) / 8);
+ gdp->bg_checksum = ext4_group_desc_csum(sbi, block_group, gdp);

return EXT4_INODES_PER_GROUP(sb);
}
@@ -118,12 +124,12 @@ 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);
@@ -131,6 +137,7 @@ 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;
@@ -144,7 +151,7 @@ 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 read. We can
@@ -161,6 +168,21 @@ 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_bitmap_csum_verify(sb, block_group,
+ desc->bg_inode_bitmap_csum, bh,
+ (EXT4_INODES_PER_GROUP(sb) + 7) / 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;
}

@@ -265,6 +287,8 @@ 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_bitmap_csum_set(sb, block_group, &gdp->bg_inode_bitmap_csum,
+ bitmap_bh, (EXT4_INODES_PER_GROUP(sb) + 7) / 8);
gdp->bg_checksum = ext4_group_desc_csum(sbi, block_group, gdp);
ext4_unlock_group(sb, block_group);

@@ -784,6 +808,9 @@ static int ext4_claim_inode(struct super_block *sb,
atomic_inc(&sbi->s_flex_groups[f].used_dirs);
}
}
+ ext4_bitmap_csum_set(sb, group, &gdp->bg_inode_bitmap_csum,
+ inode_bitmap_bh,
+ (EXT4_INODES_PER_GROUP(sb) + 7) / 8);
gdp->bg_checksum = ext4_group_desc_csum(sbi, group, gdp);
err_ret:
ext4_unlock_group(sb, group);


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