Fix out of bounds array access. #1167
Merged
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
Fixes a bug in CopyIn/CopyOut operations where out of bounds array elemets were accessed. Qubitvector thrust has a number of qubits num_qubits. When move_to_vector or copy_to_vector functions are called a temporary array or vector of size (1 << num_qubits) is created and passed to chunk_ CopyOut function. There, a number of elements (1 << chunk_qubits_) of the underlying structure are copied to this array/vector. The problem is that chunk_qubits can be larger that num_qubits, accessing values in the array or vector out of bounds. This is what was making PR Qiskit#1132 failing in CI.
|
@doichanj This a patch to fix temporarily the issue, as I got a bit lost in the structure of chunks, etc. Could you take a look to check if you see a better way to solve it? |
chriseclectic
approved these changes
Mar 2, 2021
Both are needed. This one fixes a possible out of bounds write in the array. That was causing the memory corruption we saw in Merav's PR. The other one fixes a memory leak, some memory was not freed when it should have been. It doesn't cause wrong behavior but after some time it could let the program without memory. |
|
I agree with @vvilpas, and I think there is no problem to merge both. |
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Outdated suggestions cannot be applied.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.
Summary
Fixes a bug in CopyIn/CopyOut operations where out of bounds array elemets
were accessed.
QubitvectorThrusthas a number of qubitsnum_qubits. Whenmove_to_vectororcopy_to_vectorfunctions are called a temporary array or vector of size(1 <<
num_qubits) is created and passed to chunk_ CopyOut function. There, a numberof elements (1 <<
chunk_qubits_) of the underlying structure are copied tothis array/vector. The problem is that
chunk_qubits_can be larger thatnum_qubits,accessing values in the array or vector out of bounds. This is what was making
PR #1132 failing in CI.
Details and comments
chunk_qubits_is initialized from maximum number of qubits in a list of circuit whereasnum_qubitsis initilaized as the number of qubits of a given circuit.