Skip to content

Fix out-of-bounds read in expandSparsityPattern for empty block columns #1

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
jpanetta merged 2 commits into from
Aug 10, 2026
Merged

Fix out-of-bounds read in expandSparsityPattern for empty block columns #1

Changes from 1 commit
Commits
Show all changes
2 commits
Select commit Hold shift + click to select a range
ade01a1
Fix out-of-bounds read in expandSparsityPattern for empty block columns
zfergus Jul 31, 2026
15a9283
Skip empty block columns when visiting diagonal scalar entries
zfergus Jul 31, 2026
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
6 changes: 5 additions & 1 deletion src/lib/MeshFEMSparse/SparseMatrices.hh
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -1171,7 +1171,11 @@ struct CSCMatrix {
for (_Index block_j = 0; block_j < blockHsp.n; ++block_j) {
size_t gvar_j = block_j * N;
size_t numBlocks = blockHsp.Ap[block_j + 1] - blockHsp.Ap[block_j];
bool hasDiagonal = AssumeDiagonalExists || (blockHsp.Ai[blockHsp.Ap[block_j + 1] - 1] == block_j);
// Guard against empty block columns (possible, e.g., for contact
// Hessians, where most vertices are collision-free): reading
// Ai[Ap[block_j + 1] - 1] would be out of bounds, and a spurious
// `hasDiagonal` would underflow `colSize` below.
bool hasDiagonal = (numBlocks > 0) && (AssumeDiagonalExists || (blockHsp.Ai[blockHsp.Ap[block_j + 1] - 1] == block_j));
if (hasDiagonal) {
size_t colSize = (numBlocks - 1) * N + 1;
for (size_t c_j = 0; c_j < N; ++c_j)
Expand Down