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authorFabricio Voznika <fvoznika@google.com>2021-01-21 15:38:22 -0800
committergVisor bot <gvisor-bot@google.com>2021-01-21 15:47:23 -0800
commit7bf656f4c635e4acdc0a61523220dfc9a1f3d1ba (patch)
tree26ac28ebad65eebacdb081bc4f317f99307a80f0 /runsc
parent89df5a681c004a3772facc08de73d930636227be (diff)
Fix ownership change logic
Previously fsgofer was skipping chown call if the uid and gid were the same as the current user/group. However, when setgid is set, the group may not be the same as the caller. Instead, compare the actual uid/gid of the file after it has been created and change ownership only if needed. Updates #180 PiperOrigin-RevId: 353118733
Diffstat (limited to 'runsc')
-rw-r--r--runsc/fsgofer/fsgofer.go52
-rw-r--r--runsc/fsgofer/fsgofer_test.go94
2 files changed, 112 insertions, 34 deletions
diff --git a/runsc/fsgofer/fsgofer.go b/runsc/fsgofer/fsgofer.go
index c3bba0973..f25681233 100644
--- a/runsc/fsgofer/fsgofer.go
+++ b/runsc/fsgofer/fsgofer.go
@@ -49,13 +49,6 @@ const (
allowedOpenFlags = unix.O_TRUNC
)
-var (
- // Remember the process uid/gid to skip chown calls when file owner/group
- // doesn't need to be changed.
- processUID = p9.UID(os.Getuid())
- processGID = p9.GID(os.Getgid())
-)
-
// join is equivalent to path.Join() but skips path.Clean() which is expensive.
func join(parent, child string) string {
if child == "." || child == ".." {
@@ -377,6 +370,23 @@ func fchown(fd int, uid p9.UID, gid p9.GID) error {
return unix.Fchownat(fd, "", int(uid), int(gid), linux.AT_EMPTY_PATH|unix.AT_SYMLINK_NOFOLLOW)
}
+func setOwnerIfNeeded(fd int, uid p9.UID, gid p9.GID) (unix.Stat_t, error) {
+ stat, err := fstat(fd)
+ if err != nil {
+ return unix.Stat_t{}, err
+ }
+
+ // Change ownership if not set accordinly.
+ if uint32(uid) != stat.Uid || uint32(gid) != stat.Gid {
+ if err := fchown(fd, uid, gid); err != nil {
+ return unix.Stat_t{}, err
+ }
+ stat.Uid = uint32(uid)
+ stat.Gid = uint32(gid)
+ }
+ return stat, nil
+}
+
// Open implements p9.File.
func (l *localFile) Open(flags p9.OpenFlags) (*fd.FD, p9.QID, uint32, error) {
if l.isOpen() {
@@ -457,12 +467,7 @@ func (l *localFile) Create(name string, p9Flags p9.OpenFlags, perm p9.FileMode,
})
defer cu.Clean()
- if uid != processUID || gid != processGID {
- if err := fchown(child.FD(), uid, gid); err != nil {
- return nil, nil, p9.QID{}, 0, extractErrno(err)
- }
- }
- stat, err := fstat(child.FD())
+ stat, err := setOwnerIfNeeded(child.FD(), uid, gid)
if err != nil {
return nil, nil, p9.QID{}, 0, extractErrno(err)
}
@@ -505,12 +510,7 @@ func (l *localFile) Mkdir(name string, perm p9.FileMode, uid p9.UID, gid p9.GID)
}
defer f.Close()
- if uid != processUID || gid != processGID {
- if err := fchown(f.FD(), uid, gid); err != nil {
- return p9.QID{}, extractErrno(err)
- }
- }
- stat, err := fstat(f.FD())
+ stat, err := setOwnerIfNeeded(f.FD(), uid, gid)
if err != nil {
return p9.QID{}, extractErrno(err)
}
@@ -900,12 +900,7 @@ func (l *localFile) Symlink(target, newName string, uid p9.UID, gid p9.GID) (p9.
}
defer f.Close()
- if uid != processUID || gid != processGID {
- if err := fchown(f.FD(), uid, gid); err != nil {
- return p9.QID{}, extractErrno(err)
- }
- }
- stat, err := fstat(f.FD())
+ stat, err := setOwnerIfNeeded(f.FD(), uid, gid)
if err != nil {
return p9.QID{}, extractErrno(err)
}
@@ -959,12 +954,7 @@ func (l *localFile) Mknod(name string, mode p9.FileMode, _ uint32, _ uint32, uid
}
defer child.Close()
- if uid != processUID || gid != processGID {
- if err := fchown(child.FD(), uid, gid); err != nil {
- return p9.QID{}, extractErrno(err)
- }
- }
- stat, err := fstat(child.FD())
+ stat, err := setOwnerIfNeeded(child.FD(), uid, gid)
if err != nil {
return p9.QID{}, extractErrno(err)
}
diff --git a/runsc/fsgofer/fsgofer_test.go b/runsc/fsgofer/fsgofer_test.go
index c5daebe5e..99ea9bd32 100644
--- a/runsc/fsgofer/fsgofer_test.go
+++ b/runsc/fsgofer/fsgofer_test.go
@@ -32,6 +32,9 @@ import (
"gvisor.dev/gvisor/runsc/specutils"
)
+// Nodoby is the standard UID/GID for the nobody user/group.
+const nobody = 65534
+
var allOpenFlags = []p9.OpenFlags{p9.ReadOnly, p9.WriteOnly, p9.ReadWrite}
var (
@@ -281,6 +284,92 @@ func TestCreate(t *testing.T) {
})
}
+func checkIDs(f p9.File, uid, gid int) error {
+ _, _, stat, err := f.GetAttr(p9.AttrMask{UID: true, GID: true})
+ if err != nil {
+ return fmt.Errorf("GetAttr() failed, err: %v", err)
+ }
+ if want := p9.UID(uid); stat.UID != want {
+ return fmt.Errorf("Wrong UID, want: %v, got: %v", want, stat.UID)
+ }
+ if want := p9.GID(gid); stat.GID != want {
+ return fmt.Errorf("Wrong GID, want: %v, got: %v", want, stat.GID)
+ }
+ return nil
+}
+
+// TestCreateSetGID checks files/dirs/symlinks are created with the proper
+// owner when the parent directory has setgid set,
+func TestCreateSetGID(t *testing.T) {
+ if !specutils.HasCapabilities(capability.CAP_CHOWN) {
+ t.Skipf("Test requires CAP_CHOWN")
+ }
+
+ runCustom(t, []uint32{unix.S_IFDIR}, rwConfs, func(t *testing.T, s state) {
+ // Change group and set setgid to the parent dir.
+ if err := unix.Chown(s.file.hostPath, os.Getuid(), nobody); err != nil {
+ t.Fatalf("Chown() failed: %v", err)
+ }
+ if err := unix.Chmod(s.file.hostPath, 02777); err != nil {
+ t.Fatalf("Chmod() failed: %v", err)
+ }
+
+ t.Run("create", func(t *testing.T) {
+ _, l, _, _, err := s.file.Create("test", p9.ReadOnly, 0777, p9.UID(os.Getuid()), p9.GID(os.Getgid()))
+ if err != nil {
+ t.Fatalf("WriteAt() failed: %v", err)
+ }
+ defer l.Close()
+ if err := checkIDs(l, os.Getuid(), os.Getgid()); err != nil {
+ t.Error(err)
+ }
+ })
+
+ t.Run("mkdir", func(t *testing.T) {
+ _, err := s.file.Mkdir("test-dir", 0777, p9.UID(os.Getuid()), p9.GID(os.Getgid()))
+ if err != nil {
+ t.Fatalf("WriteAt() failed: %v", err)
+ }
+ _, l, err := s.file.Walk([]string{"test-dir"})
+ if err != nil {
+ t.Fatalf("Walk() failed: %v", err)
+ }
+ defer l.Close()
+ if err := checkIDs(l, os.Getuid(), os.Getgid()); err != nil {
+ t.Error(err)
+ }
+ })
+
+ t.Run("symlink", func(t *testing.T) {
+ if _, err := s.file.Symlink("/some/target", "symlink", p9.UID(os.Getuid()), p9.GID(os.Getgid())); err != nil {
+ t.Fatalf("Symlink() failed: %v", err)
+ }
+ _, l, err := s.file.Walk([]string{"symlink"})
+ if err != nil {
+ t.Fatalf("Walk() failed, err: %v", err)
+ }
+ defer l.Close()
+ if err := checkIDs(l, os.Getuid(), os.Getgid()); err != nil {
+ t.Error(err)
+ }
+ })
+
+ t.Run("mknod", func(t *testing.T) {
+ if _, err := s.file.Mknod("nod", p9.ModeRegular|0777, 0, 0, p9.UID(os.Getuid()), p9.GID(os.Getgid())); err != nil {
+ t.Fatalf("Mknod() failed: %v", err)
+ }
+ _, l, err := s.file.Walk([]string{"nod"})
+ if err != nil {
+ t.Fatalf("Walk() failed, err: %v", err)
+ }
+ defer l.Close()
+ if err := checkIDs(l, os.Getuid(), os.Getgid()); err != nil {
+ t.Error(err)
+ }
+ })
+ })
+}
+
// TestReadWriteDup tests that a file opened in any mode can be dup'ed and
// reopened in any other mode.
func TestReadWriteDup(t *testing.T) {
@@ -458,7 +547,7 @@ func TestSetAttrTime(t *testing.T) {
}
func TestSetAttrOwner(t *testing.T) {
- if os.Getuid() != 0 {
+ if !specutils.HasCapabilities(capability.CAP_CHOWN) {
t.Skipf("SetAttr(owner) test requires CAP_CHOWN, running as %d", os.Getuid())
}
@@ -477,7 +566,7 @@ func TestSetAttrOwner(t *testing.T) {
}
func TestLink(t *testing.T) {
- if os.Getuid() != 0 {
+ if !specutils.HasCapabilities(capability.CAP_DAC_READ_SEARCH) {
t.Skipf("Link test requires CAP_DAC_READ_SEARCH, running as %d", os.Getuid())
}
runCustom(t, allTypes, rwConfs, func(t *testing.T, s state) {
@@ -995,7 +1084,6 @@ func BenchmarkCreateDiffOwner(b *testing.B) {
files := make([]p9.File, 0, 500)
fds := make([]*fd.FD, 0, 500)
gid := p9.GID(os.Getgid())
- const nobody = 65534
b.ResetTimer()
for i := 0; i < b.N; i++ {