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index/suffixarray: protect against another data corruption

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Suffix array indices x must be in range 0 <= x < len(data).
Make sure this is the case when reading them from a file.
Trivial and cheap fix. Found during fly-by reading of the code.

While at it, also fix format string in previous test.

Change-Id: I64ed31a10ca6bf103fee5b572597f4ab02a0423f
Reviewed-on: https://go-review.googlesource.com/c/go/+/771782
Reviewed-by: Robert Griesemer <gri@google.com>
LUCI-TryBot-Result: golang-scoped@luci-project-accounts.iam.gserviceaccount.com <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Mark Freeman <markfreeman@google.com>
Auto-Submit: Robert Griesemer <gri@google.com>
This commit is contained in:
Robert Griesemer 2026-04-28 15:57:18 -07:00 • committed by Gopher Robot
parent 2098279730
commit e929fb78e4
2 changed files with 24 additions and 3 deletions
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6
src/index/suffixarray/suffixarray.go
View file

@ -143,9 +143,11 @@ func readSlice(r io.Reader, buf []byte, data ints) (n int, err error) {
len := data.len()
for p := binary.MaxVarintLen64; p < size; n++ {
x, w := binary.Uvarint(buf[p:])
// prevent index-out-of-bounds panic if there are more indices than expected
// - prevent index-out-of-bounds panic if there are more indices than expected
// (was go.dev/issue/53352)
if n >= len {
// - prevent index-out-of-bounds panic in a future Lookup
// by ensuring all indices x satisfy x < len
if n >= len || x >= uint64(len) {
return n, errCorrupted
}
data.set(n, int64(x))

21
src/index/suffixarray/suffixarray_test.go
View file

@ -659,6 +659,25 @@ func TestIssue53352(t *testing.T) {
// Reading back the corrupted encoding should report an error.
// Before fixing go.dev/issue/53352, this resulted in an index-out-of-range panic.
if err := index.Read(bytes.NewBuffer(encoding)); err != errCorrupted {
t.Fatalf("got %q; want %q", err, errCorrupted)
t.Fatalf("got %v; want %v", err, errCorrupted)
}
}
func TestIndexCorruption(t *testing.T) {
data := []byte("x")
index := New(data)
var buf bytes.Buffer
if err := index.Write(&buf); err != nil {
t.Fatal(err)
}
// The index data is at the end of the encoding (see TestIssue53352 for the encoding format).
// The encoded indices i must be 0 <= i < len(data) because they are used to index into the
// data. Corrupt one and make sure we get an error when reading the encoding.
buf.Bytes()[buf.Len()-1] = byte(len(data))
// Reading back the corrupted encoding should report an error.
if err := index.Read(&buf); err != errCorrupted {
t.Fatalf("got %v; want %v", err, errCorrupted)
}
}