Gitweb:     
http://git.kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=f762e9054ff84aa90f037a49747ac61b36609d81
Commit:     f762e9054ff84aa90f037a49747ac61b36609d81
Parent:     01584fa6456dafbaf5a94ad7fb2aa3e3ecd7a7ba
Author:     Aneesh Kumar K.V <[EMAIL PROTECTED]>
AuthorDate: Wed Feb 6 01:40:09 2008 -0800
Committer:  Linus Torvalds <[EMAIL PROTECTED]>
CommitDate: Wed Feb 6 10:41:20 2008 -0800

    ext3: add block bitmap validation
    
    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 <[EMAIL PROTECTED]>
    Cc: <[EMAIL PROTECTED]>
    Signed-off-by: Andrew Morton <[EMAIL PROTECTED]>
    Signed-off-by: Linus Torvalds <[EMAIL PROTECTED]>
---
 fs/ext3/balloc.c |   78 ++++++++++++++++++++++++++++++++++++++++++++++++-----
 1 files changed, 70 insertions(+), 8 deletions(-)

diff --git a/fs/ext3/balloc.c b/fs/ext3/balloc.c
index a8ba7e8..a26e683 100644
--- a/fs/ext3/balloc.c
+++ b/fs/ext3/balloc.c
@@ -80,13 +80,57 @@ struct ext3_group_desc * ext3_get_group_desc(struct 
super_block * sb,
        return desc + offset;
 }
 
+static int ext3_valid_block_bitmap(struct super_block *sb,
+                                       struct ext3_group_desc *desc,
+                                       unsigned int block_group,
+                                       struct buffer_head *bh)
+{
+       ext3_grpblk_t offset;
+       ext3_grpblk_t next_zero_bit;
+       ext3_fsblk_t bitmap_blk;
+       ext3_fsblk_t group_first_block;
+
+       group_first_block = ext3_group_first_block_no(sb, block_group);
+
+       /* check whether block bitmap block number is set */
+       bitmap_blk = le32_to_cpu(desc->bg_block_bitmap);
+       offset = bitmap_blk - group_first_block;
+       if (!ext3_test_bit(offset, bh->b_data))
+               /* bad block bitmap */
+               goto err_out;
+
+       /* check whether the inode bitmap block number is set */
+       bitmap_blk = le32_to_cpu(desc->bg_inode_bitmap);
+       offset = bitmap_blk - group_first_block;
+       if (!ext3_test_bit(offset, bh->b_data))
+               /* bad block bitmap */
+               goto err_out;
+
+       /* check whether the inode table block number is set */
+       bitmap_blk = le32_to_cpu(desc->bg_inode_table);
+       offset = bitmap_blk - group_first_block;
+       next_zero_bit = ext3_find_next_zero_bit(bh->b_data,
+                               offset + EXT3_SB(sb)->s_itb_per_group,
+                               offset);
+       if (next_zero_bit >= offset + EXT3_SB(sb)->s_itb_per_group)
+               /* good bitmap for inode tables */
+               return 1;
+
+err_out:
+       ext3_error(sb, __FUNCTION__,
+                       "Invalid block bitmap - "
+                       "block_group = %d, block = %lu",
+                       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.
  */
@@ -95,17 +139,35 @@ read_block_bitmap(struct super_block *sb, unsigned int 
block_group)
 {
        struct ext3_group_desc * desc;
        struct buffer_head * bh = NULL;
+       ext3_fsblk_t bitmap_blk;
 
-       desc = ext3_get_group_desc (sb, block_group, NULL);
+       desc = ext3_get_group_desc(sb, block_group, NULL);
        if (!desc)
-               goto error_out;
-       bh = sb_bread(sb, le32_to_cpu(desc->bg_block_bitmap));
-       if (!bh)
-               ext3_error (sb, "read_block_bitmap",
+               return NULL;
+       bitmap_blk = le32_to_cpu(desc->bg_block_bitmap);
+       bh = sb_getblk(sb, bitmap_blk);
+       if (unlikely(!bh)) {
+               ext3_error(sb, __FUNCTION__,
                            "Cannot read block bitmap - "
                            "block_group = %d, block_bitmap = %u",
                            block_group, le32_to_cpu(desc->bg_block_bitmap));
-error_out:
+               return NULL;
+       }
+       if (likely(bh_uptodate_or_lock(bh)))
+               return bh;
+
+       if (bh_submit_read(bh) < 0) {
+               brelse(bh);
+               ext3_error(sb, __FUNCTION__,
+                           "Cannot read block bitmap - "
+                           "block_group = %d, block_bitmap = %u",
+                           block_group, le32_to_cpu(desc->bg_block_bitmap));
+               return NULL;
+       }
+       if (!ext3_valid_block_bitmap(sb, desc, block_group, bh)) {
+               brelse(bh);
+               return NULL;
+       }
        return bh;
 }
 /*
-
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