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Qu Wenruo 147a097cf0 btrfs: tree-checker: Verify location key for DIR_ITEM/DIR_INDEX
[PROBLEM]
There is a user report in the mail list, showing the following corrupted
tree blocks:

       item 62 key (486836 DIR_ITEM 2543451757) itemoff 6273 itemsize 74
               location key (4065004 INODE_ITEM 1073741824) type FILE
               transid 21397 data_len 0 name_len 44
               name: FILENAME

Note that location key, its offset should be 0 for all INODE_ITEMS.
This caused failed lookup of the inode.

[CAUSE]
That offending value, 1073741824, is 0x40000000. So this looks like a
memory bit flip.

[FIX]
This patch will enhance tree-checker to check location key of
DIR_INDEX/DIR_ITEM/XATTR_ITEM.

There are several different combinations needs to check:

- item_key.type == DIR_INDEX/DIR_ITEM

  * location_key.type == BTRFS_INODE_ITEM_KEY
    This location_key should follow the check in inode_item check.
  * location_key.type == BTRFS_ROOT_ITEM_KEY
    Despite the existing check, DIR_INDEX/DIR_ITEM can only points to
    subvolume trees.
  * All other keys are not allowed.

- item_key.type == XATTR_ITEM
  location_key should be all 0.

Reported-by: Mike Gilbert <floppymaster@gmail.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
History 2020-01-20 16:40:56 +01:00
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Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.