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Subject[PATCH 24/49] ext4: add block bitmap validation
Date
From: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>

When a new block bitmap is read from disk in read_block_bitmap()
there are a few bits that should ALWAYS be set. In particular,
the blocks given corresponding to block bitmap, inode bitmap and inode tables.
Validate the block bitmap against these blocks.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
---
fs/ext4/balloc.c | 99 ++++++++++++++++++++++++++++++++++++++++++++----------
1 files changed, 81 insertions(+), 18 deletions(-)

diff --git a/fs/ext4/balloc.c b/fs/ext4/balloc.c
index ff3428e..a9140ea 100644
--- a/fs/ext4/balloc.c
+++ b/fs/ext4/balloc.c
@@ -189,13 +189,65 @@ 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)
+{
+ ext4_grpblk_t offset;
+ ext4_grpblk_t next_zero_bit;
+ ext4_fsblk_t bitmap_blk;
+ ext4_fsblk_t group_first_block;
+
+ if (EXT4_HAS_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_FLEX_BG)) {
+ /* with FLEX_BG, the inode/block bitmaps and itable
+ * blocks may not be in the group at all
+ * so the bitmap validation will be skipped for those groups
+ * or it has to also read the block group where the bitmaps
+ * are located to verify they are set.
+ */
+ return 1;
+ }
+ group_first_block = ext4_group_first_block_no(sb, block_group);
+
+ /* check whether block bitmap block number is set */
+ bitmap_blk = ext4_block_bitmap(sb, desc);
+ offset = bitmap_blk - group_first_block;
+ if (!ext4_test_bit(offset, bh->b_data))
+ /* bad block bitmap */
+ goto err_out;
+
+ /* check whether the inode bitmap block number is set */
+ bitmap_blk = ext4_inode_bitmap(sb, desc);
+ offset = bitmap_blk - group_first_block;
+ if (!ext4_test_bit(offset, bh->b_data))
+ /* bad block bitmap */
+ goto err_out;
+
+ /* check whether the inode table block number is set */
+ bitmap_blk = ext4_inode_table(sb, desc);
+ offset = bitmap_blk - group_first_block;
+ next_zero_bit = ext4_find_next_zero_bit(bh->b_data,
+ offset + EXT4_SB(sb)->s_itb_per_group,
+ offset);
+ if (next_zero_bit >= offset + EXT4_SB(sb)->s_itb_per_group)
+ /* good bitmap for inode tables */
+ return 1;
+
+err_out:
+ ext4_error(sb, __FUNCTION__,
+ "Invalid block bitmap - "
+ "block_group = %d, block = %llu",
+ block_group, bitmap_blk);
+ return 0;
+}
/**
* read_block_bitmap()
* @sb: super block
* @block_group: given block group
*
- * Read the bitmap for a given block_group, reading into the specified
- * slot in the superblock's bitmap cache.
+ * Read the bitmap for a given block_group,and validate the
+ * bits for block/inode/inode tables are set in the bitmaps
*
* Return buffer_head on success or NULL in case of failure.
*/
@@ -210,25 +262,36 @@ read_block_bitmap(struct super_block *sb, ext4_group_t block_group)
if (!desc)
return NULL;
bitmap_blk = ext4_block_bitmap(sb, desc);
+ bh = sb_getblk(sb, bitmap_blk);
+ if (unlikely(!bh)) {
+ ext4_error(sb, __FUNCTION__,
+ "Cannot read block bitmap - "
+ "block_group = %d, block_bitmap = %llu",
+ (int)block_group, (unsigned long long)bitmap_blk);
+ return NULL;
+ }
+ if (bh_uptodate_or_lock(bh))
+ return bh;
+
if (desc->bg_flags & cpu_to_le16(EXT4_BG_BLOCK_UNINIT)) {
- bh = sb_getblk(sb, bitmap_blk);
- if (!buffer_uptodate(bh)) {
- lock_buffer(bh);
- if (!buffer_uptodate(bh)) {
- ext4_init_block_bitmap(sb, bh, block_group,
- desc);
- set_buffer_uptodate(bh);
- }
- unlock_buffer(bh);
- }
- } else {
- bh = sb_bread(sb, bitmap_blk);
+ ext4_init_block_bitmap(sb, bh, block_group, desc);
+ set_buffer_uptodate(bh);
+ unlock_buffer(bh);
+ return bh;
}
- if (!bh)
- ext4_error (sb, __FUNCTION__,
+ if (bh_submit_read(bh) < 0) {
+ brelse(bh);
+ ext4_error(sb, __FUNCTION__,
"Cannot read block bitmap - "
- "block_group = %lu, block_bitmap = %llu",
- block_group, bitmap_blk);
+ "block_group = %d, block_bitmap = %llu",
+ (int)block_group, (unsigned long long)bitmap_blk);
+ return NULL;
+ }
+ if (!ext4_valid_block_bitmap(sb, desc, block_group, bh)) {
+ brelse(bh);
+ return NULL;
+ }
+
return bh;
}
/*
--
1.5.4.rc3.31.g1271-dirty


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