Fix LZ long-match encoding overflow (#753)#753
Closed
terrelln wants to merge 2 commits into
Closed
Conversation
|
@terrelln has exported this pull request. If you are a Meta employee, you can view the originating Diff in D104838040. |
terrelln
added a commit
to terrelln/openzl
that referenced
this pull request
May 12, 2026
Summary: The LZ encoder capped `matchLength()` at `UINT16_MAX` because sequence match lengths are stored as `uint16_t`. If the match had been walked backward at least `UINT16_MAX` bytes, then the match finding process would resume at a position which had already been inserted into the hash table. This would result in match with `distance <= 0` and corruption would ensue. Differential Revision: D104838040
meta-codesync
Bot
changed the title
terrelln
force-pushed
the
export-D104838040
branch
from
f526842 to
bfe6f2f
Compare
Summary: Allow the fuzzer to find the bug in D104838040 with short inputs. I haven't gotten the fuzzer to reproduce it yet, but in theory it should be able to. Reviewed By: kevinjzhang Differential Revision: D104843371
Summary: The LZ encoder capped `matchLength()` at `UINT16_MAX` because sequence match lengths are stored as `uint16_t`. If the match had been walked backward at least `UINT16_MAX` bytes, then the match finding process would resume at a position which had already been inserted into the hash table. This would result in match with `distance <= 0` and corruption would ensue. Differential Revision: D104838040
terrelln
force-pushed
the
export-D104838040
branch
from
bfe6f2f to
36914a0
Compare
terrelln
added a commit
to terrelln/openzl
that referenced
this pull request
May 15, 2026
Summary: The LZ encoder capped `matchLength()` at `UINT16_MAX` because sequence match lengths are stored as `uint16_t`. If the match had been walked backward at least `UINT16_MAX` bytes, then the match finding process would resume at a position which had already been inserted into the hash table. This would result in match with `distance <= 0` and corruption would ensue. Reviewed By: Cyan4973 Differential Revision: D104838040
|
This pull request has been merged in 59cc558. |
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
1 participant
Add this suggestion to a batch that can be applied as a single commit.This suggestion is invalid because no changes were made to the code.Suggestions cannot be applied while the pull request is closed.Suggestions cannot be applied while viewing a subset of changes.Only one suggestion per line can be applied in a batch.Add this suggestion to a batch that can be applied as a single commit.Applying suggestions on deleted lines is not supported.You must change the existing code in this line in order to create a valid suggestion.Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be applied on multi-line comments.Suggestions cannot be applied while the pull request is queued to merge.Suggestion cannot be applied right now. Please check back later.
Summary:
The LZ encoder capped
matchLength()atUINT16_MAXbecause sequence matchlengths are stored as
uint16_t. If the match had been walked backward at leastUINT16_MAXbytes, then the match finding process would resume at a positionwhich had already been inserted into the hash table. This would result in match
with
distance <= 0and corruption would ensue.Differential Revision: D104838040