ext4: calculate and verify block bitmap checksum

Compute and verify the checksum of the block bitmap; this checksum 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>

6 files changed, 104 insertions, 8 deletions

diff --git a/fs/ext4/balloc.c b/fs/ext4/balloc.c
index 4bbd07a6fa18..0a64e4d5dbad 100644
--- a/fs/ext4/balloc.c
+++ b/fs/ext4/balloc.c
@@ -174,6 +174,8 @@ void ext4_init_block_bitmap(struct super_block *sb, struct buffer_head *bh,
                 ext4_free_inodes_set(sb, gdp, 0);
                 ext4_itable_unused_set(sb, gdp, 0);
                 memset(bh->b_data, 0xff, sb->s_blocksize);
+                ext4_block_bitmap_csum_set(sb, block_group, gdp, bh,
+                                           EXT4_BLOCKS_PER_GROUP(sb) / 8);
                 return;
         }
         memset(bh->b_data, 0, sb->s_blocksize);
@@ -210,6 +212,9 @@ void ext4_init_block_bitmap(struct super_block *sb, struct buffer_head *bh,
          */
         ext4_mark_bitmap_end(num_clusters_in_group(sb, block_group),
                              sb->s_blocksize * 8, bh->b_data);
+        ext4_block_bitmap_csum_set(sb, block_group, gdp, bh,
+                                   EXT4_BLOCKS_PER_GROUP(sb) / 8);
+        gdp->bg_checksum = ext4_group_desc_csum(sbi, block_group, gdp);
 }
 
 /* Return the number of free blocks in a block group.  It is used when
@@ -276,9 +281,9 @@ struct ext4_group_desc * ext4_get_group_desc(struct super_block *sb,
 }
 
 static int ext4_valid_block_bitmap(struct super_block *sb,
-                                        struct ext4_group_desc *desc,
-                                        unsigned int block_group,
-                                        struct buffer_head *bh)
+                                   struct ext4_group_desc *desc,
+                                   unsigned int block_group,
+                                   struct buffer_head *bh)
 {
         ext4_grpblk_t offset;
         ext4_grpblk_t next_zero_bit;
@@ -325,6 +330,23 @@ err_out:
                         block_group, bitmap_blk);
         return 0;
 }
+
+void ext4_validate_block_bitmap(struct super_block *sb,
+                               struct ext4_group_desc *desc,
+                               unsigned int block_group,
+                               struct buffer_head *bh)
+{
+        if (buffer_verified(bh))
+                return;
+
+        ext4_lock_group(sb, block_group);
+        if (ext4_valid_block_bitmap(sb, desc, block_group, bh) &&
+            ext4_block_bitmap_csum_verify(sb, block_group, desc, bh,
+                                          EXT4_BLOCKS_PER_GROUP(sb) / 8))
+                set_buffer_verified(bh);
+        ext4_unlock_group(sb, block_group);
+}
+
 /**
  * ext4_read_block_bitmap()
  * @sb:                 super block
@@ -355,12 +377,12 @@ ext4_read_block_bitmap_nowait(struct super_block *sb, ext4_group_t block_group)
         }
 
         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);
         if (desc->bg_flags & cpu_to_le16(EXT4_BG_BLOCK_UNINIT)) {
@@ -379,7 +401,7 @@ ext4_read_block_bitmap_nowait(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
@@ -390,6 +412,9 @@ ext4_read_block_bitmap_nowait(struct super_block *sb, ext4_group_t block_group)
         get_bh(bh);
         submit_bh(READ, bh);
         return bh;
+verify:
+        ext4_validate_block_bitmap(sb, desc, block_group, bh);
+        return bh;
 }
 
 /* Returns 0 on success, 1 on error */
@@ -412,7 +437,7 @@ int ext4_wait_block_bitmap(struct super_block *sb, ext4_group_t block_group,
         }
         clear_buffer_new(bh);
         /* Panic or remount fs read-only if block bitmap is invalid */
-        ext4_valid_block_bitmap(sb, desc, block_group, bh);
+        ext4_validate_block_bitmap(sb, desc, block_group, bh);
         return 0;
 }
 
diff --git a/fs/ext4/bitmap.c b/fs/ext4/bitmap.c
index 5813e7f2e2c6..b319721da26a 100644
--- a/fs/ext4/bitmap.c
+++ b/fs/ext4/bitmap.c
@@ -68,3 +68,47 @@ void ext4_inode_bitmap_csum_set(struct super_block *sb, ext4_group_t group,
         if (sbi->s_desc_size >= EXT4_BG_INODE_BITMAP_CSUM_HI_END)
                 gdp->bg_inode_bitmap_csum_hi = cpu_to_le16(csum >> 16);
 }
+
+int ext4_block_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_block_bitmap_csum_lo);
+        calculated = ext4_chksum(sbi, sbi->s_csum_seed, (__u8 *)bh->b_data, sz);
+        if (sbi->s_desc_size >= EXT4_BG_BLOCK_BITMAP_CSUM_HI_END) {
+                hi = le16_to_cpu(gdp->bg_block_bitmap_csum_hi);
+                provided |= (hi << 16);
+        } else
+                calculated &= 0xFFFF;
+
+        if (provided == calculated)
+                return 1;
+
+        ext4_error(sb, "Bad block bitmap checksum: block_group = %u", group);
+        return 0;
+}
+
+void ext4_block_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_block_bitmap_csum_lo = cpu_to_le16(csum & 0xFFFF);
+        if (sbi->s_desc_size >= EXT4_BG_BLOCK_BITMAP_CSUM_HI_END)
+                gdp->bg_block_bitmap_csum_hi = cpu_to_le16(csum >> 16);
+}
diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 7f0ff88f32ba..7a4f16075257 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -1857,8 +1857,18 @@ void ext4_inode_bitmap_csum_set(struct super_block *sb, ext4_group_t group,
 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);
+void ext4_block_bitmap_csum_set(struct super_block *sb, ext4_group_t group,
+                                struct ext4_group_desc *gdp,
+                                struct buffer_head *bh, int sz);
+int ext4_block_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 void ext4_validate_block_bitmap(struct super_block *sb,
+                                       struct ext4_group_desc *desc,
+                                       unsigned int block_group,
+                                       struct buffer_head *bh);
 extern unsigned int ext4_block_group(struct super_block *sb,
                         ext4_fsblk_t blocknr);
 extern ext4_grpblk_t ext4_block_group_offset(struct super_block *sb,
diff --git a/fs/ext4/ialloc.c b/fs/ext4/ialloc.c
index fb897ec183c8..a6383fcb714b 100644
--- a/fs/ext4/ialloc.c
+++ b/fs/ext4/ialloc.c
@@ -753,6 +753,10 @@ got:
                         gdp->bg_flags &= cpu_to_le16(~EXT4_BG_BLOCK_UNINIT);
                         ext4_free_group_clusters_set(sb, gdp,
                                 ext4_free_clusters_after_init(sb, group, gdp));
+                        ext4_block_bitmap_csum_set(sb, group, gdp,
+                                                   block_bitmap_bh,
+                                                   EXT4_BLOCKS_PER_GROUP(sb) /
+                                                   8);
                         gdp->bg_checksum = ext4_group_desc_csum(sbi, group,
                                                                 gdp);
                 }
diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index 99ab428bcfa0..95a388fef397 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -788,7 +788,7 @@ static int ext4_mb_init_cache(struct page *page, char *incore)
         int first_block;
         struct super_block *sb;
         struct buffer_head *bhs;
-        struct buffer_head **bh;
+        struct buffer_head **bh = NULL;
         struct inode *inode;
         char *data;
         char *bitmap;
@@ -2797,6 +2797,8 @@ ext4_mb_mark_diskspace_used(struct ext4_allocation_context *ac,
         }
         len = ext4_free_group_clusters(sb, gdp) - ac->ac_b_ex.fe_len;
         ext4_free_group_clusters_set(sb, gdp, len);
+        ext4_block_bitmap_csum_set(sb, ac->ac_b_ex.fe_group, gdp, bitmap_bh,
+                                   EXT4_BLOCKS_PER_GROUP(sb) / 8);
         gdp->bg_checksum = ext4_group_desc_csum(sbi, ac->ac_b_ex.fe_group, gdp);
 
         ext4_unlock_group(sb, ac->ac_b_ex.fe_group);
@@ -4659,6 +4661,8 @@ do_more:
 
         ret = ext4_free_group_clusters(sb, gdp) + count_clusters;
         ext4_free_group_clusters_set(sb, gdp, ret);
+        ext4_block_bitmap_csum_set(sb, block_group, gdp, bitmap_bh,
+                                   EXT4_BLOCKS_PER_GROUP(sb) / 8);
         gdp->bg_checksum = ext4_group_desc_csum(sbi, block_group, gdp);
         ext4_unlock_group(sb, block_group);
         percpu_counter_add(&sbi->s_freeclusters_counter, count_clusters);
@@ -4803,6 +4807,8 @@ int ext4_group_add_blocks(handle_t *handle, struct super_block *sb,
         mb_free_blocks(NULL, &e4b, bit, count);
         blk_free_count = blocks_freed + ext4_free_group_clusters(sb, desc);
         ext4_free_group_clusters_set(sb, desc, blk_free_count);
+        ext4_block_bitmap_csum_set(sb, block_group, desc, bitmap_bh,
+                                   EXT4_BLOCKS_PER_GROUP(sb) / 8);
         desc->bg_checksum = ext4_group_desc_csum(sbi, block_group, desc);
         ext4_unlock_group(sb, block_group);
         percpu_counter_add(&sbi->s_freeclusters_counter,
diff --git a/fs/ext4/resize.c b/fs/ext4/resize.c
index 7810cac241e1..dc597e066308 100644
--- a/fs/ext4/resize.c
+++ b/fs/ext4/resize.c
@@ -1107,6 +1107,13 @@ static int ext4_set_bitmap_checksums(struct super_block *sb,
                                    EXT4_INODES_PER_GROUP(sb) / 8);
         brelse(bh);
 
+        bh = ext4_get_bitmap(sb, group_data->block_bitmap);
+        if (!bh)
+                return -EIO;
+        ext4_block_bitmap_csum_set(sb, group, gdp, bh,
+                                   EXT4_BLOCKS_PER_GROUP(sb) / 8);
+        brelse(bh);
+
         return 0;
 }