linux-ext4 - [patch 245/260] ext3: add block bitmap validation

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Message-Id: <200802060939.m169doBL004767@imap1.linux-foundation.org>
Date:	Wed, 06 Feb 2008 01:40:09 -0800
From:	akpm@...ux-foundation.org
To:	torvalds@...ux-foundation.org
Cc:	akpm@...ux-foundation.org, aneesh.kumar@...ux.vnet.ibm.com,
	linux-ext4@...r.kernel.org
Subject: [patch 245/260] ext3: add block bitmap validation

From: "Aneesh Kumar K.V" <aneesh.kumar@...ux.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@...ux.vnet.ibm.com>
Cc: <linux-ext4@...r.kernel.org>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
---

 fs/ext3/balloc.c |   78 ++++++++++++++++++++++++++++++++++++++++-----
 1 file changed, 70 insertions(+), 8 deletions(-)

diff -puN fs/ext3/balloc.c~ext3-add-block-bitmap-validation fs/ext3/balloc.c
--- a/fs/ext3/balloc.c~ext3-add-block-bitmap-validation
+++ a/fs/ext3/balloc.c
@@ -80,13 +80,57 @@ struct ext3_group_desc * ext3_get_group_
 	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
 {
 	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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