[PATCH 0/5] btrfs: Enhanced runtime defence against fuzzed images

Qu Wenruo
2019-07-10T08:02:53Z

Another wave of defence enhancment, including:

- Enhanced eb accessors
Not really needed for the fuzzed images, as 448de471cd4c
("btrfs: Check the first key and level for cached extent buffer")
already fixed half of the reported images.
Just add a final layer of safe net.

- BUG_ON() hunt in __btrfs_free_extent()
Kill BUG_ON()s in __btrfs_free_extent(), replace with error reporting
and why it shouldn't happen.

Also add comment on what __btrfs_free_extent() is designed to do, with
two dump-tree examples for newcomers.

- BUG_ON() hunt in __btrfs_inc_extent_ref()
Just like __btrfs_free_extent(), but less comment as
comment for __btrfs_free_extent() should also work for
__btrfs_inc_extent_ref(), and __btrfs_inc_extent_ref() has a better
structure than __btrfs_free_extent().

- Defence against unbalanced empty leaf

- Defence against bad key order across two tree blocks

The last two cases can't be rejected by tree-checker and they are all
cross-eb cases.
Thankfully we can reuse existing first_key check against unbalanced
empty leaf, but needs extra check deep into ctree.c for tree block
merging time check.

Reported-by: Jungyeon Yoon <jungyeon.yoon@gmail.com>
[ Not to mail bombarding the report, thus only RB tag in cover letter ]

Qu Wenruo (5):
btrfs: extent_io: Do extra check for extent buffer read write
functions
btrfs: extent-tree: Kill BUG_ON() in __btrfs_free_extent() and do
better comment
btrfs: Detect unbalanced tree with empty leaf before crashing btree
operations
btrfs: extent-tree: Kill the BUG_ON() in
insert_inline_extent_backref()
btrfs: ctree: Checking key orders before merged tree blocks

fs/btrfs/ctree.c | 63 +++++++++++++++
fs/btrfs/disk-io.c | 9 +++
fs/btrfs/extent-tree.c | 168 ++++++++++++++++++++++++++++++++++++----
fs/btrfs/extent_io.c | 79 ++++++++++---------
fs/btrfs/tree-checker.c | 6 ++
5 files changed, 273 insertions(+), 52 deletions(-)

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2.22.0