From d2901f9efd4b1b26c995ea1c61663a14bc9c55d6 Mon Sep 17 00:00:00 2001
From: jingrui <jingrui@huawei.com>
Date: Thu, 3 Jan 2019 16:25:23 +0800
Subject: [PATCH 045/111] overlay:  safely remove overlay layer
 directory

reason: cherry-pick commits to docker-18.09

merge from
0af3bf355a * safely remove overlay layer directory
e2b1d6827b * docker: add link string validation

---
safely remove overlay layer directory

do not recover link if the format is illegal
do not remove illegal link string

Signed-off-by: Deng Guangxing <dengguangxing@huawei.com>
---
docker: add link string validation

validate link string with restrict reqirements, not just stringLen.
Shukui Yang

Signed-off-by: Deng Guangxing <dengguangxing@huawei.com>
Signed-off-by: yangshukui <yangshukui@huawei.com>

Change-Id: Ie4f47b942c7e89bd6632d310c1cb34533ed5726b
Signed-off-by: jingrui <jingrui@huawei.com>
---
 .../daemon/graphdriver/overlay2/overlay.go    | 30 +++++++++++++++++--
 .../daemon/graphdriver/overlay2/randomid.go   |  7 +++++
 2 files changed, 34 insertions(+), 3 deletions(-)

diff --git a/components/engine/daemon/graphdriver/overlay2/overlay.go b/components/engine/daemon/graphdriver/overlay2/overlay.go
index 722d65b11a..773d5232cc 100644
--- a/components/engine/daemon/graphdriver/overlay2/overlay.go
+++ b/components/engine/daemon/graphdriver/overlay2/overlay.go
@@ -419,6 +419,10 @@ func (d *Driver) create(id, parent string, opts *graphdriver.CreateOpts) (retErr
 	}
 
 	lid := generateID(idLength)
+	if !verifyID(lid, idLength) {
+		// this should never happen
+		return fmt.Errorf("[overlay2], generated link string(%s) illegal", lid)
+	}
 	if err := os.Symlink(path.Join("..", id, "diff"), path.Join(d.home, linkDir, lid)); err != nil {
 		return err
 	}
@@ -491,6 +495,9 @@ func (d *Driver) getLower(parent string) (string, error) {
 	if err != nil {
 		return "", err
 	}
+	if !verifyID(string(parentLink), idLength) {
+		return "", fmt.Errorf("illegal link string: %s", parentLink)
+	}
 	lowers := []string{path.Join(linkDir, string(parentLink))}
 
 	parentLower, err := ioutil.ReadFile(path.Join(parentDir, lowerFile))
@@ -570,7 +577,7 @@ func (d *Driver) Remove(id string) error {
 	dir := d.dir(id)
 	lid, err := ioutil.ReadFile(path.Join(dir, "link"))
 	if err == nil {
-		if len(lid) == 0 {
+		if !verifyID(string(lid), idLength) {
 			logrus.WithField("storage-driver", "overlay2").Errorf("refusing to remove empty link for layer %v", id)
 		} else if err := os.RemoveAll(path.Join(d.home, linkDir, string(lid))); err != nil {
 			logrus.WithField("storage-driver", "overlay2").Debugf("Failed to remove link: %v", err)
@@ -703,8 +710,25 @@ func (d *Driver) Put(id string) error {
 
 // Exists checks to see if the id is already mounted.
 func (d *Driver) Exists(id string) bool {
-	_, err := os.Stat(d.dir(id))
-	return err == nil
+	_, rerr := os.Stat(d.dir(id))
+	if rerr == nil {
+		lstr, err := ioutil.ReadFile(path.Join(d.dir(id), "link"))
+		// link is valid
+		if err == nil && verifyID(string(lstr), idLength) {
+			// check symlink
+			_, rerr = os.Stat(path.Join(d.home, linkDir, string(lstr)))
+			if rerr != nil {
+				os.RemoveAll(path.Join(d.home, linkDir, string(lstr)))
+
+				logrus.Infof("[overlay2]: symlink (%s) is missing, create a new one", lstr)
+				if rerr = os.Symlink(path.Join("..", id, "diff"), path.Join(d.home, linkDir, string(lstr))); rerr != nil {
+					return false
+				}
+			}
+			return true
+		}
+	}
+	return false
 }
 
 // isParent determines whether the given parent is the direct parent of the
diff --git a/components/engine/daemon/graphdriver/overlay2/randomid.go b/components/engine/daemon/graphdriver/overlay2/randomid.go
index 842c06127f..933d9fccb6 100644
--- a/components/engine/daemon/graphdriver/overlay2/randomid.go
+++ b/components/engine/daemon/graphdriver/overlay2/randomid.go
@@ -8,6 +8,7 @@ import (
 	"fmt"
 	"io"
 	"os"
+	"regexp"
 	"syscall"
 	"time"
 
@@ -79,3 +80,9 @@ func retryOnError(err error) bool {
 
 	return false
 }
+
+func verifyID(id string, l int) bool {
+	regstr := fmt.Sprintf("^[A-Z0-9]{%d}$", l)
+	rgxp := regexp.MustCompile(regstr)
+	return rgxp.MatchString(id)
+}
-- 
2.17.1