Fix integer overflow checks in enumerator#15829
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nobu merged 1 commit intoruby:masterfrom Jan 9, 2026
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❌ 3/67208 Tests Failedtest/-ext-/stack/test_stack_overflow.rb#test_fiber_stack_overflowtest/-ext-/stack/test_stack_overflow.rb#test_overflowtest/-ext-/stack/test_stack_overflow.rb#test_thread_stack_overflow |
nobu
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Please remove unrelated and unnecessary commits first.
regparse.c
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| if ((size_t)i > (size_t)ONIGENC_CODE_TO_MBC_MAXLEN) { | ||
| r = ONIGERR_TOO_SHORT_MULTI_BYTE_STRING; | ||
| goto err; | ||
| } | ||
|
|
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Here i should equal ONIGENC_MBC_MINLEN(env->enc), this check is redundant.
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ext/-test-/stack/stack.c
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| // Allocate and touch memory to force actual stack usage: | ||
| volatile char *stack = alloca(1024); | ||
| // Allocate and touch memory to force actual memory usage: | ||
| char *buf = (char *)malloc(1024); | ||
| if (!buf) { | ||
| break; | ||
| } | ||
| volatile char *stack = buf; | ||
| stack[0] = (char)i; | ||
| stack[1023] = (char)i; | ||
| i++; | ||
| free(buf); |
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This is intentionally repeating alloca to cause a stack overflow, as the function name and the comment describe.
This change doesn't only break the purpose, falls into an infinite loop.
This was referenced Feb 6, 2026
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fix this kind of problem you must avoid performing a signed addition that may overflow and then using its result in a comparison. Instead, reformulate the condition in terms of inequalities that do not overflow, or perform the addition in a wider or unsigned type where overflow is either impossible or well‑defined, and then convert back safely.
For this specific case, the intention of
if (i + unit < i) break;(forunit >= 0) is to stop the loop if incrementingibyunitwould overflow the signedlongrange. A safe, equivalent check is to compareiagainstLONG_MAX - unit: ifi > LONG_MAX - unit, theni + unitwould exceedLONG_MAXand overflow. Similarly, in theunit < 0branch, the intention ofif (i + unit > i) break;is to detect overflow when adding a negativeunit; the safe equivalent is to checki < LONG_MIN - unit(sinceunitis negative,LONG_MIN - unitis well‑defined and ≥LONG_MIN), meaning that addingunitwould go belowLONG_MIN.Concretely, in the first loop (for
unit >= 0) at line 4011, replaceif (i + unit < i) break;withif (i > LONG_MAX - unit) break;. In the second loop (forunit < 0) at line 4024, replaceif (i + unit > i) break;withif (i < LONG_MIN - unit) break;. These changes preserve existing behavior while avoiding undefined signed overflow. To useLONG_MAXandLONG_MIN, we need<limits.h>. Since we cannot assume it is already included and we’re allowed to add standard headers, add#include <limits.h>near the other#includes at the top of enumerator.c.References
comp.lang.c FAQ list · Question 3.19 (Preserving rules)
INT31-C. Ensure that integer conversions do not result in lost or misinterpreted data
Integer Overflow in C/C++