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    Subject[PATCH 15/28] ext4: Calculate and verify block bitmap checksum
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    Date
    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>
    ---
    fs/ext4/balloc.c | 40 +++++++++++++++++++++------
    fs/ext4/bitmap.c | 40 +++++++++++++++++++++++++++
    fs/ext4/ext4.h | 10 +++++++
    fs/ext4/ialloc.c | 4 +++
    fs/ext4/mballoc.c | 78 +++++++++++++++++++++++++++++++++++++++++++++--------
    5 files changed, 151 insertions(+), 21 deletions(-)


    diff --git a/fs/ext4/balloc.c b/fs/ext4/balloc.c
    index f8224ad..dd96a7d 100644
    --- a/fs/ext4/balloc.c
    +++ b/fs/ext4/balloc.c
    @@ -105,6 +105,9 @@ unsigned 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 0;
    }
    memset(bh->b_data, 0, sb->s_blocksize);
    @@ -175,6 +178,10 @@ unsigned ext4_init_block_bitmap(struct super_block *sb, struct buffer_head *bh,
    */
    ext4_mark_bitmap_end(group_blocks, 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 free_blocks - ext4_group_used_meta_blocks(sb, block_group, gdp);
    }
    @@ -232,10 +239,10 @@ struct ext4_group_desc * ext4_get_group_desc(struct super_block *sb,
    return desc;
    }

    -static int ext4_valid_block_bitmap(struct super_block *sb,
    - struct ext4_group_desc *desc,
    - unsigned int block_group,
    - struct buffer_head *bh)
    +int ext4_valid_block_bitmap(struct super_block *sb,
    + struct ext4_group_desc *desc,
    + unsigned int block_group,
    + struct buffer_head *bh)
    {
    ext4_grpblk_t offset;
    ext4_grpblk_t next_zero_bit;
    @@ -312,12 +319,12 @@ ext4_read_block_bitmap(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)) {
    @@ -336,7 +343,7 @@ ext4_read_block_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
    @@ -353,11 +360,26 @@ ext4_read_block_bitmap(struct super_block *sb, ext4_group_t block_group)
    block_group, bitmap_blk);
    return NULL;
    }
    - ext4_valid_block_bitmap(sb, desc, block_group, bh);
    +
    +verify:
    + if (buffer_verified(bh))
    + return bh;
    /*
    * file system mounted not to panic on error,
    - * continue with corrupt bitmap
    + * -EIO with corrupt bitmap
    */
    + 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)) {
    + ext4_unlock_group(sb, block_group);
    + put_bh(bh);
    + ext4_error(sb, "Corrupt block bitmap - block_group = %u, "
    + "block_bitmap = %llu", block_group, bitmap_blk);
    + return NULL;
    + }
    + ext4_unlock_group(sb, block_group);
    + set_buffer_verified(bh);
    return bh;
    }

    diff --git a/fs/ext4/bitmap.c b/fs/ext4/bitmap.c
    index e9342f6..00ebc7a 100644
    --- a/fs/ext4/bitmap.c
    +++ b/fs/ext4/bitmap.c
    @@ -81,3 +81,43 @@ 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_LOCATION)
    gdp->bg_inode_bitmap_csum_hi = cpu_to_le16(crc >> 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_bitmap_csum(sb, group, bh, sz);
    + if (sbi->s_desc_size >= EXT4_BG_BLOCK_BITMAP_CSUM_HI_LOCATION) {
    + hi = le16_to_cpu(gdp->bg_block_bitmap_csum_hi);
    + provided |= (hi << 16);
    + } else
    + calculated &= 0xFFFF;
    +
    + return provided == calculated;
    +}
    +
    +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 crc;
    + struct ext4_sb_info *sbi = EXT4_SB(sb);
    +
    + if (!EXT4_HAS_RO_COMPAT_FEATURE(sb,
    + EXT4_FEATURE_RO_COMPAT_METADATA_CSUM))
    + return;
    +
    + crc = ext4_bitmap_csum(sb, group, bh, sz);
    + gdp->bg_block_bitmap_csum_lo = cpu_to_le16(crc & 0xFFFF);
    + if (sbi->s_desc_size >= EXT4_BG_BLOCK_BITMAP_CSUM_HI_LOCATION)
    + gdp->bg_block_bitmap_csum_hi = cpu_to_le16(crc >> 16);
    +}
    diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
    index c98bc9f..7cd3541 100644
    --- a/fs/ext4/ext4.h
    +++ b/fs/ext4/ext4.h
    @@ -1776,8 +1776,18 @@ 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 int ext4_valid_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 6fb00e7..77ae3df 100644
    --- a/fs/ext4/ialloc.c
    +++ b/fs/ext4/ialloc.c
    @@ -981,6 +981,10 @@ got:
    free = ext4_free_blocks_after_init(sb, group, gdp);
    gdp->bg_flags &= cpu_to_le16(~EXT4_BG_BLOCK_UNINIT);
    ext4_free_blks_set(sb, gdp, free);
    + 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 17a5a57..3d6300a 100644
    --- a/fs/ext4/mballoc.c
    +++ b/fs/ext4/mballoc.c
    @@ -753,6 +753,44 @@ void ext4_mb_generate_buddy(struct super_block *sb,
    spin_unlock(&EXT4_SB(sb)->s_bal_lock);
    }

    +struct ext4_csum_data {
    + struct super_block *cd_sb;
    + ext4_group_t cd_group;
    +};
    +
    +static void ext4_end_buffer_read_sync(struct buffer_head *bh, int uptodate)
    +{
    + struct ext4_group_desc *desc;
    + struct super_block *sb =
    + ((struct ext4_csum_data *)bh->b_private)->cd_sb;
    + ext4_group_t group = ((struct ext4_csum_data *)bh->b_private)->cd_group;
    +
    + if (!uptodate)
    + goto out;
    +
    + desc = ext4_get_group_desc(sb, group, NULL);
    + if (!desc)
    + goto out;
    +
    + if (buffer_verified(bh))
    + goto out;
    +
    + ext4_lock_group(sb, group);
    + if (!ext4_valid_block_bitmap(sb, desc, group, bh) ||
    + !ext4_block_bitmap_csum_verify(sb, group, desc, bh,
    + EXT4_BLOCKS_PER_GROUP(sb) / 8)) {
    + ext4_unlock_group(sb, group);
    + ext4_error(sb, "Corrupt block bitmap, group = %u", group);
    + goto out;
    + }
    + ext4_unlock_group(sb, group);
    + set_buffer_verified(bh);
    +
    +out:
    + bh->b_private = NULL;
    + end_buffer_read_sync(bh, uptodate);
    +}
    +
    /* The buddy information is attached the buddy cache inode
    * for convenience. The information regarding each group
    * is loaded via ext4_mb_load_buddy. The information involve
    @@ -785,11 +823,12 @@ 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;
    struct ext4_group_info *grinfo;
    + struct ext4_csum_data *csd;

    mb_debug(1, "init page %lu\n", page->index);

    @@ -803,6 +842,11 @@ static int ext4_mb_init_cache(struct page *page, char *incore)
    if (groups_per_page == 0)
    groups_per_page = 1;

    + csd = kzalloc(sizeof(struct ext4_csum_data) * groups_per_page,
    + GFP_NOFS);
    + if (csd == NULL)
    + goto out;
    +
    /* allocate buffer_heads to read bitmaps */
    if (groups_per_page > 1) {
    err = -ENOMEM;
    @@ -880,22 +924,25 @@ static int ext4_mb_init_cache(struct page *page, char *incore)
    * get set with buffer lock held.
    */
    set_bitmap_uptodate(bh[i]);
    - bh[i]->b_end_io = end_buffer_read_sync;
    + csd[i].cd_sb = sb;
    + csd[i].cd_group = first_group + i;
    + bh[i]->b_private = csd + i;
    + bh[i]->b_end_io = ext4_end_buffer_read_sync;
    submit_bh(READ, bh[i]);
    mb_debug(1, "read bitmap for group %u\n", first_group + i);
    }

    - /* wait for I/O completion */
    - for (i = 0; i < groups_per_page; i++)
    - if (bh[i])
    - wait_on_buffer(bh[i]);
    -
    - err = -EIO;
    - for (i = 0; i < groups_per_page; i++)
    - if (bh[i] && !buffer_uptodate(bh[i]))
    - goto out;
    -
    + /* Wait for I/O completion and checksum verification */
    err = 0;
    + for (i = 0; i < groups_per_page; i++) {
    + if (bh[i] == NULL)
    + continue;
    + wait_on_buffer(bh[i]);
    + if (!buffer_uptodate(bh[i]) ||
    + !buffer_verified(bh[i]))
    + err = -EIO;
    + }
    +
    first_block = page->index * blocks_per_page;
    for (i = 0; i < blocks_per_page; i++) {
    int group;
    @@ -972,6 +1019,7 @@ out:
    if (bh != &bhs)
    kfree(bh);
    }
    + kfree(csd);
    return err;
    }

    @@ -2829,6 +2877,8 @@ ext4_mb_mark_diskspace_used(struct ext4_allocation_context *ac,
    }
    len = ext4_free_blks_count(sb, gdp) - ac->ac_b_ex.fe_len;
    ext4_free_blks_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);
    @@ -4638,6 +4688,8 @@ do_more:

    ret = ext4_free_blks_count(sb, gdp) + count;
    ext4_free_blks_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_freeblocks_counter, count);
    @@ -4780,6 +4832,8 @@ 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_blks_count(sb, desc);
    ext4_free_blks_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_freeblocks_counter, blocks_freed);


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