[GH-ISSUE #412] get_env<int> returns uninitialized data for malformed values #187

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opened 2026-10-26 21:14:27 +00:00 by bsakaguchi · 1 comment

bsakaguchi commented

2026-10-26 21:14:27 +00:00

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Originally created by @OllieinCanada on GitHub (Aug 24, 2026).
Original GitHub issue: https://github.com/deepseek-ai/DeepGEMM/issues/412

Summary

get_env<int> ignores the return value of std::sscanf and returns an uninitialized local when an environment variable is set to a non-numeric value:

int value;
std::sscanf(c_str, "%d", &value);
return value;

If parsing fails, value is never initialized and reading it is undefined behavior. The unset case is safe because it returns the configured default before reaching this branch.

Impact

The helper is used by more than twenty C++ configuration reads. Most are debug flags, where malformed values can unexpectedly enable logging. DG_JIT_CPP_STANDARD is more consequential: a plausible value such as c++17 fails %d parsing and can put an indeterminate standard number into the JIT compiler command.

The same parser bug was independently reported in deepseek-ai/DeepEP#733.

Expected behavior

Integer environment variables should be parsed deterministically. Malformed, partially parsed, and out-of-range values should fail clearly instead of returning uninitialized or truncated data.

Proposed fix

Use a full-consumption, range-checked integer parser and cover it with a host-only C++ regression test. The test should require no CUDA toolkit or GPU and should cover valid signs/whitespace/bounds plus empty, boolean, hex-like, trailing-junk, and overflow inputs.

Originally created by @OllieinCanada on GitHub (Aug 24, 2026). Original GitHub issue: https://github.com/deepseek-ai/DeepGEMM/issues/412 ## Summary `get_env<int>` ignores the return value of `std::sscanf` and returns an uninitialized local when an environment variable is set to a non-numeric value: ```cpp int value; std::sscanf(c_str, "%d", &value); return value; ``` If parsing fails, `value` is never initialized and reading it is undefined behavior. The unset case is safe because it returns the configured default before reaching this branch. ## Impact The helper is used by more than twenty C++ configuration reads. Most are debug flags, where malformed values can unexpectedly enable logging. `DG_JIT_CPP_STANDARD` is more consequential: a plausible value such as `c++17` fails `%d` parsing and can put an indeterminate standard number into the JIT compiler command. The same parser bug was independently reported in deepseek-ai/DeepEP#733. ## Expected behavior Integer environment variables should be parsed deterministically. Malformed, partially parsed, and out-of-range values should fail clearly instead of returning uninitialized or truncated data. ## Proposed fix Use a full-consumption, range-checked integer parser and cover it with a host-only C++ regression test. The test should require no CUDA toolkit or GPU and should cover valid signs/whitespace/bounds plus empty, boolean, hex-like, trailing-junk, and overflow inputs.

bsakaguchi commented

2026-10-26 21:14:30 +00:00

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@XFDG commented on GitHub (Sep 12, 2026):

I independently rechecked current main at 66081d4c9c. The old csrc/utils/system.hpp implementation is no longer present, and DeepGEMM pins third-party/deep_jit at e5bdee2bc4ca519eba00cfc5f0c6e950e6a96a16. In that pinned revision, include/deep_jit/utils/env.hpp parses integral values with std::from_chars and rejects both parse errors and partial consumption (position != end).

So the original uninitialized-return and partial-parse paths are no longer reachable on current main. This appears resolved by the DeepJIT migration; a follow-up patch should not restore the deleted DeepGEMM utility.

@XFDG commented on GitHub (Sep 12, 2026): I independently rechecked current main at 66081d4c9c7d7c44f13fea402e5b622aa0f409c2. The old csrc/utils/system.hpp implementation is no longer present, and DeepGEMM pins third-party/deep_jit at e5bdee2bc4ca519eba00cfc5f0c6e950e6a96a16. In that pinned revision, include/deep_jit/utils/env.hpp parses integral values with std::from_chars and rejects both parse errors and partial consumption (position != end). So the original uninitialized-return and partial-parse paths are no longer reachable on current main. This appears resolved by the DeepJIT migration; a follow-up patch should not restore the deleted DeepGEMM utility.

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