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internal/saferio: handle potential total size overflow in SliceCap

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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>
This commit is contained in:
Zeke Lu 2022-09-26 14:53:54 +00:00 committed by Gopher Robot
parent bd8a5b00fc
commit 4da2bc2eeb
2 changed files with 12 additions and 2 deletions
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7
src/internal/saferio/io.go
View File

@ -121,8 +121,11 @@ func SliceCap(v any, c uint64) int {
if typ.Kind() != reflect.Ptr { if typ.Kind() != reflect.Ptr {
panic("SliceCap called with non-pointer type") panic("SliceCap called with non-pointer type")
} }
size := typ.Elem().Size() size := uint64(typ.Elem().Size())
if uintptr(c)*size > chunk { if size > 0 && c > (1<<64-1)/size {
return -1
}
if c*size > chunk {
c = uint64(chunk / size) c = uint64(chunk / size)
if c == 0 { if c == 0 {
c = 1 c = 1

7
src/internal/saferio/io_test.go
View File

@ -126,4 +126,11 @@ func TestSliceCap(t *testing.T) {
t.Errorf("SliceCap returned %d, expected failure", c) t.Errorf("SliceCap returned %d, expected failure", c)
} }
}) })
t.Run("overflow", func(t *testing.T) {
c := SliceCap((*int64)(nil), 1<<62)
if c >= 0 {
t.Errorf("SliceCap returned %d, expected failure", c)
}
})
} }