Fix WasmPtr to work with accesses accessing the final valid byte #1272
Conversation
This file contains 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
This also returns `None` for all accesses of zero sized types and arrays of length 0. Because the array accesses have a non-inclusive length, length of 0 is not valid. These checks prevent returning empty slices that point just outside of memory bounds.
MarkMcCaskey
force-pushed
the
fix/wasmptr-last-byte-access
branch
from
490c2ac
to
f8d34e0
Compare
syrusakbary
approved these changes
Mar 5, 2020
|
bors r+ |
Build succeeded |
|
👍 |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
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Outdated suggestions cannot be applied.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.
Resolves #1258
The fix was to change
>=into>. Doing this made us vulnerable to accessing memory to create an empty slice just out of bounds so we have to add some additional checks to make sure that that can't happen.This PR also prevents accessing arrays of length 0 (the length bound is non-inclusive, so length 0 is never valid) and prevents access of zero-sized types.
The zero-sized type checks will probably be inlined (or will be in the future as
const fngets more mature) so provide no additional overhead. The checking of if length == 0 does add some overhead, but on modern CPUs it shouldn't be an issue as it's a branch that should be always false in normal use.Review