Merge release-20210601.0-47-g0892420c9 (automated)

1 files changed, 29 insertions, 4 deletions

diff --git a/pkg/sentry/vfs/memxattr/xattr.go b/pkg/sentry/vfs/memxattr/xattr.go
index 638b5d830..9b7953fa3 100644
--- a/pkg/sentry/vfs/memxattr/xattr.go
+++ b/pkg/sentry/vfs/memxattr/xattr.go
@@ -17,7 +17,10 @@
 package memxattr
 
 import (
+	"strings"
+
 	"gvisor.dev/gvisor/pkg/abi/linux"
+	"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
 	"gvisor.dev/gvisor/pkg/sentry/vfs"
 	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/syserror"
@@ -26,6 +29,9 @@ import (
 // SimpleExtendedAttributes implements extended attributes using a map of
 // names to values.
 //
+// SimpleExtendedAttributes calls vfs.CheckXattrPermissions, so callers are not
+// required to do so.
+//
 // +stateify savable
 type SimpleExtendedAttributes struct {
 	// mu protects the below fields.
@@ -34,7 +40,11 @@ type SimpleExtendedAttributes struct {
 }
 
 // GetXattr returns the value at 'name'.
-func (x *SimpleExtendedAttributes) GetXattr(opts *vfs.GetXattrOptions) (string, error) {
+func (x *SimpleExtendedAttributes) GetXattr(creds *auth.Credentials, mode linux.FileMode, kuid auth.KUID, opts *vfs.GetXattrOptions) (string, error) {
+	if err := vfs.CheckXattrPermissions(creds, vfs.MayRead, mode, kuid, opts.Name); err != nil {
+		return "", err
+	}
+
 	x.mu.RLock()
 	value, ok := x.xattrs[opts.Name]
 	x.mu.RUnlock()
@@ -50,7 +60,11 @@ func (x *SimpleExtendedAttributes) GetXattr(opts *vfs.GetXattrOptions) (string,
 }
 
 // SetXattr sets 'value' at 'name'.
-func (x *SimpleExtendedAttributes) SetXattr(opts *vfs.SetXattrOptions) error {
+func (x *SimpleExtendedAttributes) SetXattr(creds *auth.Credentials, mode linux.FileMode, kuid auth.KUID, opts *vfs.SetXattrOptions) error {
+	if err := vfs.CheckXattrPermissions(creds, vfs.MayWrite, mode, kuid, opts.Name); err != nil {
+		return err
+	}
+
 	x.mu.Lock()
 	defer x.mu.Unlock()
 	if x.xattrs == nil {
@@ -73,12 +87,19 @@ func (x *SimpleExtendedAttributes) SetXattr(opts *vfs.SetXattrOptions) error {
 }
 
 // ListXattr returns all names in xattrs.
-func (x *SimpleExtendedAttributes) ListXattr(size uint64) ([]string, error) {
+func (x *SimpleExtendedAttributes) ListXattr(creds *auth.Credentials, size uint64) ([]string, error) {
 	// Keep track of the size of the buffer needed in listxattr(2) for the list.
 	listSize := 0
 	x.mu.RLock()
 	names := make([]string, 0, len(x.xattrs))
+	haveCap := creds.HasCapability(linux.CAP_SYS_ADMIN)
 	for n := range x.xattrs {
+		// Hide extended attributes in the "trusted" namespace from
+		// non-privileged users. This is consistent with Linux's
+		// fs/xattr.c:simple_xattr_list().
+		if !haveCap && strings.HasPrefix(n, linux.XATTR_TRUSTED_PREFIX) {
+			continue
+		}
 		names = append(names, n)
 		// Add one byte per null terminator.
 		listSize += len(n) + 1
@@ -91,7 +112,11 @@ func (x *SimpleExtendedAttributes) ListXattr(size uint64) ([]string, error) {
 }
 
 // RemoveXattr removes the xattr at 'name'.
-func (x *SimpleExtendedAttributes) RemoveXattr(name string) error {
+func (x *SimpleExtendedAttributes) RemoveXattr(creds *auth.Credentials, mode linux.FileMode, kuid auth.KUID, name string) error {
+	if err := vfs.CheckXattrPermissions(creds, vfs.MayWrite, mode, kuid, name); err != nil {
+		return err
+	}
+
 	x.mu.Lock()
 	defer x.mu.Unlock()
 	if _, ok := x.xattrs[name]; !ok {