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internal/saferio: handle potential total size overflow in SliceCap
Before the change, "SliceCap((*int64)(nil), 1<<62)" returns 1<<62.
That's because "uintptr(c)*size" overflows and gives 0 which is less
than the "chunk". SliceCap should return -1 in this case.
Change-Id: I4e99224c8ac0fc72032c6be86d7318d33d083cd8
GitHub-Last-Rev: ca30bcce45
GitHub-Pull-Request: golang/go#55870
Reviewed-on: https://go-review.googlesource.com/c/go/+/434335
Reviewed-by: Ian Lance Taylor <iant@google.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Auto-Submit: Ian Lance Taylor <iant@google.com>
Run-TryBot: Ian Lance Taylor <iant@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
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@ -121,8 +121,11 @@ func SliceCap(v any, c uint64) int {
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if typ.Kind() != reflect.Ptr {
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panic("SliceCap called with non-pointer type")
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}
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size := typ.Elem().Size()
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if uintptr(c)*size > chunk {
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size := uint64(typ.Elem().Size())
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if size > 0 && c > (1<<64-1)/size {
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return -1
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}
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if c*size > chunk {
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c = uint64(chunk / size)
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if c == 0 {
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c = 1
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@ -126,4 +126,11 @@ func TestSliceCap(t *testing.T) {
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t.Errorf("SliceCap returned %d, expected failure", c)
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}
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})
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t.Run("overflow", func(t *testing.T) {
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c := SliceCap((*int64)(nil), 1<<62)
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if c >= 0 {
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t.Errorf("SliceCap returned %d, expected failure", c)
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}
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})
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}
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