Reject negative ROM lengths in uvm32_load#12
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ringtailsoftware merged 1 commit intoJul 16, 2026
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uvm32_load accepted negative int lengths and forwarded them to the size_t copy parameter. Reject them alongside oversized ROMs so invalid input follows the existing false return path. Constraint: Keep the public int signature and existing zero/exact-fit behavior Rejected: Change len to size_t | unnecessary API and ABI change Confidence: high Scope-risk: narrow Directive: Validate signed lengths before passing them to size_t APIs Tested: Hook boundary matrix on MinGW GCC 8 and WSL GCC 13; Unity badcode 2/2; stack-protection configuration; WSL ASan/UBSan; git diff --check Not-tested: Full Docker suite locally because the RISC-V cross compiler and Docker service were unavailable
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Summary
Problem
uvm32_load() accepts len as an int, but currently checks only whether it exceeds UVM32_MEMORY_SIZE. A negative value therefore reaches UVM32_MEMCPY, whose length parameter is size_t, after an unintended signed-to-unsigned conversion.
Negative byte counts have no valid meaning for this API. Checking the lower bound before the copy keeps invalid input consistent with the existing oversized-ROM behavior without changing the public signature.
Testing
A non-copying UVM32_MEMCPY recording hook linked the real uvm32.c and exercised INT_MIN, -1, 0, 1, exact fit, and one byte over the limit.
On current main, INT_MIN and -1 both returned true and invoked the copy hook once. With this change they return false without invoking it; all non-negative boundary results remain unchanged.
Verified with:
Limitations
The full Docker suite was not available locally because this machine does not have the repository's RISC-V cross compiler and its Docker service is not running. The pull request CI will run that complete environment.