From 974073a2e5203ea34976c76336cbd212c78fa6e3 Mon Sep 17 00:00:00 2001
From: Klaus Post <klauspost@gmail.com>
Date: Thu, 14 Oct 2021 10:19:17 -0700
Subject: [PATCH] directio: Check if buffers are set. (#13440)

Check if directio buffers have actually been fetched and prevent errors on double Close. Return error on Read after Close.

Fixes

```
panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x0 pc=0xf8582f]

goroutine 210 [running]:
github.com/minio/minio/internal/ioutil.(*ODirectReader).Read(0xc0054f8320, {0xc0014560b0, 0xa8, 0x44d012})
	github.com/minio/minio/internal/ioutil/odirect_reader.go:88 +0x10f
io.ReadAtLeast({0x428c5c0, 0xc0054f8320}, {0xc0014560b0, 0xa8, 0xa8}, 0xa8)
	io/io.go:328 +0x9a
io.ReadFull(...)
	io/io.go:347
github.com/minio/minio/internal/ioutil.ReadFile({0xc001bf60e0, 0x6})
	github.com/minio/minio/internal/ioutil/read_file.go:48 +0x19b
github.com/minio/minio/cmd.(*FSObjects).scanBucket.func1({{0xc00444e1e0, 0x4d}, 0x0, {0xc0040cf240, 0xe}, {0xc0040cf24f, 0x18}, {0xc0040cf268, 0x18}, 0x0, ...})
	github.com/minio/minio/cmd/fs-v1.go:366 +0x1ea
github.com/minio/minio/cmd.(*folderScanner).scanFolder.func1({0xc00474a6a8, 0xc0065d6793}, 0x0)
	github.com/minio/minio/cmd/data-scanner.go:494 +0xb15
github.com/minio/minio/cmd.readDirFn({0xc002803e80, 0x34}, 0xc000670270)
	github.com/minio/minio/cmd/os-readdir_unix.go:172 +0x638
github.com/minio/minio/cmd.(*folderScanner).scanFolder(0xc002deeb40, {0x42dc9d0, 0xc00068cbc0}, {{0xc001c6e2d0, 0x27}, 0xc0023db8e0, 0x1}, 0xc0001c7ab0)
	github.com/minio/minio/cmd/data-scanner.go:427 +0xa8f
github.com/minio/minio/cmd.(*folderScanner).scanFolder.func2({{0xc001c6e2d0, 0x27}, 0xc0023db8e0, 0x27})
	github.com/minio/minio/cmd/data-scanner.go:549 +0xd0
github.com/minio/minio/cmd.(*folderScanner).scanFolder(0xc002deeb40, {0x42dc9d0, 0xc00068cbc0}, {{0xc0013fa9e0, 0xe}, 0x0, 0x1}, 0xc000670dd8)
	github.com/minio/minio/cmd/data-scanner.go:623 +0x205d
github.com/minio/minio/cmd.scanDataFolder({_, _}, {_, _}, {{{0xc0013fa9e0, 0xe}, 0x802, {0x210f15d2, 0xed8f903b8, 0x5bc0e80}, ...}, ...}, ...)
	github.com/minio/minio/cmd/data-scanner.go:333 +0xc51
github.com/minio/minio/cmd.(*FSObjects).scanBucket(_, {_, _}, {_, _}, {{{0xc0013fa9e0, 0xe}, 0x802, {0x210f15d2, 0xed8f903b8, ...}, ...}, ...})
	github.com/minio/minio/cmd/fs-v1.go:364 +0x305
github.com/minio/minio/cmd.(*FSObjects).NSScanner(0x42dc9d0, {0x42dc9d0, 0xc00068cbc0}, 0x0, 0xc003bcfda0, 0x802)
	github.com/minio/minio/cmd/fs-v1.go:307 +0xa16
github.com/minio/minio/cmd.runDataScanner({0x42dc9d0, 0xc00068cbc0}, {0x436a6c0, 0xc000bfcf50})
	github.com/minio/minio/cmd/data-scanner.go:150 +0x749
created by github.com/minio/minio/cmd.initDataScanner
	github.com/minio/minio/cmd/data-scanner.go:73 +0xb0
```
---
 cmd/utils.go                      |  2 +-
 internal/ioutil/odirect_reader.go | 13 +++++++++----
 2 files changed, 10 insertions(+), 5 deletions(-)

diff --git a/cmd/utils.go b/cmd/utils.go
index d5a44c2b2..30d6d0e3b 100644
--- a/cmd/utils.go
+++ b/cmd/utils.go
@@ -42,7 +42,7 @@ import (
 	"sync"
 	"time"
 
-	humanize "github.com/dustin/go-humanize"
+	"github.com/dustin/go-humanize"
 	"github.com/gorilla/mux"
 	"github.com/minio/madmin-go"
 	miniogopolicy "github.com/minio/minio-go/v7/pkg/policy"
diff --git a/internal/ioutil/odirect_reader.go b/internal/ioutil/odirect_reader.go
index aaffca784..c51f82fc7 100644
--- a/internal/ioutil/odirect_reader.go
+++ b/internal/ioutil/odirect_reader.go
@@ -122,10 +122,15 @@ func (o *ODirectReader) Read(buf []byte) (n int, err error) {
 
 // Close - Release the buffer and close the file.
 func (o *ODirectReader) Close() error {
-	if o.SmallFile {
-		ODirectPoolSmall.Put(o.bufp)
-	} else {
-		ODirectPoolLarge.Put(o.bufp)
+	if o.bufp != nil {
+		if o.SmallFile {
+			ODirectPoolSmall.Put(o.bufp)
+		} else {
+			ODirectPoolLarge.Put(o.bufp)
+		}
+		o.bufp = nil
+		o.buf = nil
 	}
+	o.err = errors.New("internal error: ODirectReader Read after Close")
 	return o.File.Close()
 }