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database/sql: buffers provided to Rows.Next should not be modified by drivers

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Previously we allowed drivers to modify the row buffer used to scan
values when closing Rows. This is no longer acceptable and can lead
to data races.

Fixes #23519

Change-Id: I91820a6266ffe52f95f40bb47307d375727715af
Reviewed-on: https://go-review.googlesource.com/89936
Run-TryBot: Daniel Theophanes <kardianos@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>
This commit is contained in:
Daniel Theophanes 2018-01-25 10:50:02 -08:00
parent 7350297eb6
commit 651ddbdb50
4 changed files with 14 additions and 42 deletions
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7
doc/go1.10.html
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@ -814,6 +814,13 @@ formats the X.509 distinguished name in the standard RFC 2253 format.
<dl id="database/sql/driver"><dt><a href="/pkg/database/sql/driver/">database/sql/driver</a></dt>
<dd>
<p>
Drivers that currently hold on to the destination buffer provdied by
<a href="/pkg/database/sql/driver/#Rows.Next"><code>driver.Rows.Next</code></a> should ensure they no longer
write to a buffer assignedd to the destination array outside of that call.
Drivers must be careful that underlying buffers are not modified when closing
<a href="/pkg/database/sql/driver/#Rows"><code>driver.Rows</code></a>.
</p>
<p>
Drivers that want to construct a <a href="/pkg/database/sql/#DB"><code>sql.DB</code></a> for
their clients can now implement the <a href="/pkg/database/sql/driver/#Connector"><code>Connector</code></a> interface
and call the new <a href="/pkg/database/sql/#OpenDB"><code>sql.OpenDB</code></a> function,

4
src/database/sql/driver/driver.go
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@ -379,6 +379,10 @@ type Rows interface {
// size as the Columns() are wide.
//
// Next should return io.EOF when there are no more rows.
//
// The dest should not be written to outside of Next. Care
// should be taken when closing Rows not to modify
// a buffer held in dest.
Next(dest []Value) error
}

5
src/database/sql/fakedb_test.go
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@ -1020,11 +1020,6 @@ func (rc *rowsCursor) touchMem() {
}
func (rc *rowsCursor) Close() error {
if !rc.closed {
for _, bs := range rc.bytesClone {
bs[0] = 255 // first byte corrupted
}
}
rc.touchMem()
rc.parentMem.touchMem()
rc.closed = true

40
src/database/sql/sql_test.go
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@ -663,43 +663,6 @@ func TestPoolExhaustOnCancel(t *testing.T) {
}
}
func TestByteOwnership(t *testing.T) {
db := newTestDB(t, "people")
defer closeDB(t, db)
rows, err := db.Query("SELECT|people|name,photo|")
if err != nil {
t.Fatalf("Query: %v", err)
}
type row struct {
name []byte
photo RawBytes
}
got := []row{}
for rows.Next() {
var r row
err = rows.Scan(&r.name, &r.photo)
if err != nil {
t.Fatalf("Scan: %v", err)
}
got = append(got, r)
}
corruptMemory := []byte("\xffPHOTO")
want := []row{
{name: []byte("Alice"), photo: corruptMemory},
{name: []byte("Bob"), photo: corruptMemory},
{name: []byte("Chris"), photo: corruptMemory},
}
if !reflect.DeepEqual(got, want) {
t.Errorf("mismatch.\n got: %#v\nwant: %#v", got, want)
}
var photo RawBytes
err = db.QueryRow("SELECT|people|photo|name=?", "Alice").Scan(&photo)
if err == nil {
t.Error("want error scanning into RawBytes from QueryRow")
}
}
func TestRowsColumns(t *testing.T) {
db := newTestDB(t, "people")
defer closeDB(t, db)
@ -3192,8 +3155,11 @@ func TestIssue18429(t *testing.T) {
// reported.
rows, _ := tx.QueryContext(ctx, "WAIT|"+qwait+"|SELECT|people|name|")
if rows != nil {
var name string
// Call Next to test Issue 21117 and check for races.
for rows.Next() {
// Scan the buffer so it is read and checked for races.
rows.Scan(&name)
}
rows.Close()
}