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[code-scanning-fix] Fix go/incorrect-integer-conversion: integer truncation in stableHash #42696

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pelikhan merged 3 commits into from
Jul 1, 2026
+26 −1
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[code-scanning-fix] Fix go/incorrect-integer-conversion: integer truncation in stableHash #42696

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a093c10
fix: prevent integer truncation in stableHash (go/incorrect-integer-c…
github-actions[bot] Jul 1, 2026
c4c4c57
docs: clarify stableHash contract for non-positive modulo values
Copilot Jul 1, 2026
cf952da
fix: add regression tests and warning log for stableHash edge cases
Copilot Jul 1, 2026
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9 changes: 8 additions & 1 deletion pkg/parser/schedule_fuzzy_scatter.go
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Original file line number Diff line number Diff line change
Expand Up @@ -168,6 +168,7 @@ func avoidPeakMinutes(hour, minute int) int {

// stableHash returns a deterministic hash value in the range [0, modulo)
// using FNV-1a hash algorithm, which is stable across platforms and Go versions.
// If modulo is <= 0, stableHash returns 0 (the range is empty/invalid).
func stableHash(s string, modulo int) int {
h := fnv.New32a()
// hash.Hash.Write never returns an error in practice, but check to satisfy gosec G104
Expand All @@ -176,7 +177,13 @@ func stableHash(s string, modulo int) int {
scheduleFuzzyScatterLog.Printf("Warning: hash write failed: %v", err)
return 0
}
return int(h.Sum32() % uint32(modulo))
if modulo <= 0 {
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scheduleFuzzyScatterLog.Printf("Warning: stableHash called with non-positive modulo %d, returning 0", modulo)
return 0
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}
// Use int64 arithmetic to avoid truncation when modulo exceeds math.MaxUint32
// on 64-bit platforms where int is 64 bits wide.
return int(int64(h.Sum32()) % int64(modulo))
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}

// ScatterSchedule takes a fuzzy cron expression and a workflow identifier
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18 changes: 18 additions & 0 deletions pkg/parser/schedule_fuzzy_scatter_test.go
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Expand Up @@ -4,6 +4,7 @@ package parser

import (
"fmt"
"math"
"strings"
"testing"
)
Expand Down Expand Up @@ -557,6 +558,23 @@ func TestStableHash(t *testing.T) {
if hash1 == hash3 {
t.Logf("Warning: different strings produced same hash (rare but possible)")
}

// Test zero modulo returns 0 (guard against divide-by-zero)
if got := stableHash("any", 0); got != 0 {
t.Errorf("stableHash(_, 0) = %d, want 0", got)
}

// Test negative modulo returns 0 safely
if got := stableHash("any", -1); got != 0 {
t.Errorf("stableHash(_, -1) = %d, want 0", got)
}

// Test modulo larger than math.MaxUint32 to guard against truncation regression
const largeModulo = math.MaxUint32 + 1 // 4_294_967_296
hashLarge := stableHash("test-workflow", largeModulo)
if hashLarge < 0 || hashLarge >= largeModulo {
t.Errorf("stableHash out of range for large modulo: got %d, want [0, %d)", hashLarge, largeModulo)
}
}

func TestScatterScheduleWeekdays(t *testing.T) {
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