ext4: check for allocation block validity with block group locked (8d5a803c) · Commits · 戴 / test

With commit : "ext4: don't update checksum of new initialized bitmaps" the buffer valid bit will get set without actually setting up the checksum for the allocation bitmap, since the checksum will get calculated once we actually allocate an inode or block. If we are doing this, then we need to (re-)check the verified bit after we take the block group lock. Otherwise, we could race with another process reading and verifying the bitmap, which would then complain about the checksum being invalid. https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1780137 Signed-off-by:

Theodore Ts'o <tytso@mit.edu> Cc: stable@kernel.org

fs/ext4/balloc.c

+3 −0

Original line number	Diff line number	Diff line
		@@ -368,6 +368,8 @@ static int ext4_validate_block_bitmap(struct super_block *sb,
		return -EFSCORRUPTED;

		ext4_lock_group(sb, block_group);
		if (buffer_verified(bh))
		goto verified;
		if (unlikely(!ext4_block_bitmap_csum_verify(sb, block_group,
		desc, bh))) {
		ext4_unlock_group(sb, block_group);
		@@ -386,6 +388,7 @@ static int ext4_validate_block_bitmap(struct super_block *sb,
		return -EFSCORRUPTED;
		}
		set_buffer_verified(bh);
		verified:
		ext4_unlock_group(sb, block_group);
		return 0;
		}

fs/ext4/ialloc.c

+3 −0

Original line number	Diff line number	Diff line
		@@ -90,6 +90,8 @@ static int ext4_validate_inode_bitmap(struct super_block *sb,
		return -EFSCORRUPTED;

		ext4_lock_group(sb, block_group);
		if (buffer_verified(bh))
		goto verified;
		blk = ext4_inode_bitmap(sb, desc);
		if (!ext4_inode_bitmap_csum_verify(sb, block_group, desc, bh,
		EXT4_INODES_PER_GROUP(sb) / 8)) {
		@@ -101,6 +103,7 @@ static int ext4_validate_inode_bitmap(struct super_block *sb,
		return -EFSBADCRC;
		}
		set_buffer_verified(bh);
		verified:
		ext4_unlock_group(sb, block_group);
		return 0;
		}

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