Merge pull request #489 from ivo1116/fix-docker-workdir-nonexistent-home-directory

Fix working directory for Docker images without home directories

Author: ameowlia

rundmc/processes/builder.go

@@ -1,6 +1,9 @@
 package processes
 
 import (
+	"os"
+	"path/filepath"
+
 	"code.cloudfoundry.org/garden"
 	"code.cloudfoundry.org/guardian/rundmc/goci"
 	"code.cloudfoundry.org/guardian/rundmc/users"
@@ -45,7 +48,7 @@ func (p *ProcBuilder) BuildProcess(bndl goci.Bndl, spec garden.ProcessSpec, user
 			AdditionalGids: additionalGIDs,
 			Username:       spec.User,
 		},
-		Cwd:             spec.Dir,
+		Cwd:             getRootDir(bndl.RootFS(), spec.Dir, user.Home),
 		Capabilities:    p.capabilities(bndl, user.Gid),
 		Rlimits:         toRlimits(spec.Limits),
 		Terminal:        spec.TTY != nil,
@@ -103,3 +106,21 @@ func toUint32Slice(slice []int) []uint32 {
 	}
 	return result
 }
+
+func getRootDir(rootFS, specDir, home string) string {
+	dir := specDir
+	if dir == "" {
+		dir = home
+	}
+
+	if dir == "" {
+		return "/"
+	}
+
+	fullPath := filepath.Join(rootFS, dir)
+	if _, err := os.Stat(fullPath); os.IsNotExist(err) {
+		return "/"
+	}
+
+	return dir
+}

rundmc/processes/builder_test.go

@@ -1,6 +1,9 @@
 package processes_test
 
 import (
+	"os"
+	"path/filepath"
+
 	"code.cloudfoundry.org/garden"
 	"code.cloudfoundry.org/guardian/rundmc/goci"
 	"code.cloudfoundry.org/guardian/rundmc/processes"
@@ -21,13 +24,20 @@ var _ = Describe("ProcBuilder", func() {
 		bndl        goci.Bndl
 		processSpec garden.ProcessSpec
 		user        *users.ExecUser
+		tmpRootFS   string
 	)
 
 	BeforeEach(func() {
+		var err error
+		tmpRootFS, err = os.MkdirTemp("", "rootfs")
+		Expect(err).NotTo(HaveOccurred())
+		Expect(os.MkdirAll(filepath.Join(tmpRootFS, "dir"), 0755)).To(Succeed())
+
 		envDeterminer = new(fakes.FakeEnvDeterminer)
 		envDeterminer.EnvForReturns([]string{"ENV"})
 
 		bndl = goci.Bundle().
+			WithRootFS(tmpRootFS).
 			WithHostname("some-hostname").
 			WithUIDMappings(specs.LinuxIDMapping{
 				ContainerID: 0,
@@ -73,6 +83,10 @@ var _ = Describe("ProcBuilder", func() {
 		}
 	})
 
+	AfterEach(func() {
+		Expect(os.RemoveAll(tmpRootFS)).To(Succeed())
+	})
+
 	Describe("the built process", func() {
 		var preparedProc *specs.Process
 
@@ -207,6 +221,86 @@ var _ = Describe("ProcBuilder", func() {
 			})
 		})
 	})
+
+	Describe("working directory resolution", func() {
+		var (
+			preparedProc *specs.Process
+			tmpRootFS    string
+		)
+
+		BeforeEach(func() {
+			var err error
+			tmpRootFS, err = os.MkdirTemp("", "rootfs")
+			Expect(err).NotTo(HaveOccurred())
+
+			bndl = bndl.WithRootFS(tmpRootFS)
+		})
+
+		AfterEach(func() {
+			Expect(os.RemoveAll(tmpRootFS)).To(Succeed())
+		})
+
+		JustBeforeEach(func() {
+			procBuilder = processes.NewBuilder(envDeterminer, nonRootMaxCaps)
+			preparedProc = procBuilder.BuildProcess(bndl, processSpec, user)
+		})
+
+		Context("when spec.Dir is set", func() {
+			BeforeEach(func() {
+				processSpec.Dir = "/app"
+			})
+
+			Context("and the directory exists", func() {
+				BeforeEach(func() {
+					Expect(os.MkdirAll(filepath.Join(tmpRootFS, "app"), 0755)).To(Succeed())
+				})
+
+				It("uses spec.Dir as Cwd", func() {
+					Expect(preparedProc.Cwd).To(Equal("/app"))
+				})
+			})
+
+			Context("and the directory does not exist", func() {
+				It("falls back to '/'", func() {
+					Expect(preparedProc.Cwd).To(Equal("/"))
+				})
+			})
+		})
+
+		Context("when spec.Dir is empty", func() {
+			BeforeEach(func() {
+				processSpec.Dir = ""
+				user.Home = "/home/robot"
+			})
+
+			Context("and the home directory exists", func() {
+				BeforeEach(func() {
+					Expect(os.MkdirAll(filepath.Join(tmpRootFS, "home", "robot"), 0755)).To(Succeed())
+				})
+
+				It("uses home directory as Cwd", func() {
+					Expect(preparedProc.Cwd).To(Equal("/home/robot"))
+				})
+			})
+
+			Context("and the home directory does not exist", func() {
+				It("falls back to '/'", func() {
+					Expect(preparedProc.Cwd).To(Equal("/"))
+				})
+			})
+		})
+
+		Context("when both spec.Dir and home are empty", func() {
+			BeforeEach(func() {
+				processSpec.Dir = ""
+				user.Home = ""
+			})
+
+			It("falls back to '/'", func() {
+				Expect(preparedProc.Cwd).To(Equal("/"))
+			})
+		})
+	})
 })
 
 func ptr(i uint64) *uint64 {