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-rw-r--r--pkg/abi/linux/xattr.go6
-rw-r--r--pkg/sentry/fsimpl/gofer/gofer.go23
-rw-r--r--pkg/sentry/fsimpl/tmpfs/filesystem.go2
-rw-r--r--pkg/sentry/fsimpl/tmpfs/tmpfs.go57
-rw-r--r--pkg/sentry/vfs/memxattr/BUILD1
-rw-r--r--pkg/sentry/vfs/memxattr/xattr.go33
6 files changed, 83 insertions, 39 deletions
diff --git a/pkg/abi/linux/xattr.go b/pkg/abi/linux/xattr.go
index 8ef837f27..1fa7a4f4f 100644
--- a/pkg/abi/linux/xattr.go
+++ b/pkg/abi/linux/xattr.go
@@ -23,6 +23,12 @@ const (
XATTR_CREATE = 1
XATTR_REPLACE = 2
+ XATTR_SECURITY_PREFIX = "security."
+ XATTR_SECURITY_PREFIX_LEN = len(XATTR_SECURITY_PREFIX)
+
+ XATTR_SYSTEM_PREFIX = "system."
+ XATTR_SYSTEM_PREFIX_LEN = len(XATTR_SYSTEM_PREFIX)
+
XATTR_TRUSTED_PREFIX = "trusted."
XATTR_TRUSTED_PREFIX_LEN = len(XATTR_TRUSTED_PREFIX)
diff --git a/pkg/sentry/fsimpl/gofer/gofer.go b/pkg/sentry/fsimpl/gofer/gofer.go
index 21692d2ac..cf69e1b7a 100644
--- a/pkg/sentry/fsimpl/gofer/gofer.go
+++ b/pkg/sentry/fsimpl/gofer/gofer.go
@@ -1282,9 +1282,12 @@ func (d *dentry) checkPermissions(creds *auth.Credentials, ats vfs.AccessTypes)
}
func (d *dentry) checkXattrPermissions(creds *auth.Credentials, name string, ats vfs.AccessTypes) error {
- // We only support xattrs prefixed with "user." (see b/148380782). Currently,
- // there is no need to expose any other xattrs through a gofer.
- if !strings.HasPrefix(name, linux.XATTR_USER_PREFIX) {
+ // Deny access to the "security" and "system" namespaces since applications
+ // may expect these to affect kernel behavior in unimplemented ways
+ // (b/148380782). Allow all other extended attributes to be passed through
+ // to the remote filesystem. This is inconsistent with Linux's 9p client,
+ // but consistent with other filesystems (e.g. FUSE).
+ if strings.HasPrefix(name, linux.XATTR_SECURITY_PREFIX) || strings.HasPrefix(name, linux.XATTR_SYSTEM_PREFIX) {
return syserror.EOPNOTSUPP
}
mode := linux.FileMode(atomic.LoadUint32(&d.mode))
@@ -1684,7 +1687,7 @@ func (d *dentry) setDeleted() {
}
func (d *dentry) listXattr(ctx context.Context, creds *auth.Credentials, size uint64) ([]string, error) {
- if d.file.isNil() || !d.userXattrSupported() {
+ if d.file.isNil() {
return nil, nil
}
xattrMap, err := d.file.listXattr(ctx, size)
@@ -1693,10 +1696,7 @@ func (d *dentry) listXattr(ctx context.Context, creds *auth.Credentials, size ui
}
xattrs := make([]string, 0, len(xattrMap))
for x := range xattrMap {
- // We only support xattrs in the user.* namespace.
- if strings.HasPrefix(x, linux.XATTR_USER_PREFIX) {
- xattrs = append(xattrs, x)
- }
+ xattrs = append(xattrs, x)
}
return xattrs, nil
}
@@ -1731,13 +1731,6 @@ func (d *dentry) removeXattr(ctx context.Context, creds *auth.Credentials, name
return d.file.removeXattr(ctx, name)
}
-// Extended attributes in the user.* namespace are only supported for regular
-// files and directories.
-func (d *dentry) userXattrSupported() bool {
- filetype := linux.FileMode(atomic.LoadUint32(&d.mode)).FileType()
- return filetype == linux.ModeRegular || filetype == linux.ModeDirectory
-}
-
// Preconditions:
// * !d.isSynthetic().
// * d.isRegularFile() || d.isDir().
diff --git a/pkg/sentry/fsimpl/tmpfs/filesystem.go b/pkg/sentry/fsimpl/tmpfs/filesystem.go
index ee7ff2961..f0f4297ef 100644
--- a/pkg/sentry/fsimpl/tmpfs/filesystem.go
+++ b/pkg/sentry/fsimpl/tmpfs/filesystem.go
@@ -822,7 +822,7 @@ func (fs *filesystem) ListXattrAt(ctx context.Context, rp *vfs.ResolvingPath, si
if err != nil {
return nil, err
}
- return d.inode.listXattr(size)
+ return d.inode.listXattr(rp.Credentials(), size)
}
// GetXattrAt implements vfs.FilesystemImpl.GetXattrAt.
diff --git a/pkg/sentry/fsimpl/tmpfs/tmpfs.go b/pkg/sentry/fsimpl/tmpfs/tmpfs.go
index 9ae25ce9e..6b4367c42 100644
--- a/pkg/sentry/fsimpl/tmpfs/tmpfs.go
+++ b/pkg/sentry/fsimpl/tmpfs/tmpfs.go
@@ -717,44 +717,63 @@ func (i *inode) touchCMtimeLocked() {
atomic.StoreInt64(&i.ctime, now)
}
-func (i *inode) listXattr(size uint64) ([]string, error) {
- return i.xattrs.ListXattr(size)
+func checkXattrName(name string) error {
+ // Linux's tmpfs supports "security" and "trusted" xattr namespaces, and
+ // (depending on build configuration) POSIX ACL xattr namespaces
+ // ("system.posix_acl_access" and "system.posix_acl_default"). We don't
+ // support POSIX ACLs or the "security" namespace (b/148380782).
+ if strings.HasPrefix(name, linux.XATTR_TRUSTED_PREFIX) {
+ return nil
+ }
+ // We support the "user" namespace because we have tests that depend on
+ // this feature.
+ if strings.HasPrefix(name, linux.XATTR_USER_PREFIX) {
+ return nil
+ }
+ return syserror.EOPNOTSUPP
+}
+
+func (i *inode) listXattr(creds *auth.Credentials, size uint64) ([]string, error) {
+ return i.xattrs.ListXattr(creds, size)
}
func (i *inode) getXattr(creds *auth.Credentials, opts *vfs.GetXattrOptions) (string, error) {
- if err := i.checkXattrPermissions(creds, opts.Name, vfs.MayRead); err != nil {
+ if err := checkXattrName(opts.Name); err != nil {
return "", err
}
- return i.xattrs.GetXattr(opts)
+ mode := linux.FileMode(atomic.LoadUint32(&i.mode))
+ kuid := auth.KUID(atomic.LoadUint32(&i.uid))
+ kgid := auth.KGID(atomic.LoadUint32(&i.gid))
+ if err := vfs.GenericCheckPermissions(creds, vfs.MayRead, mode, kuid, kgid); err != nil {
+ return "", err
+ }
+ return i.xattrs.GetXattr(creds, mode, kuid, opts)
}
func (i *inode) setXattr(creds *auth.Credentials, opts *vfs.SetXattrOptions) error {
- if err := i.checkXattrPermissions(creds, opts.Name, vfs.MayWrite); err != nil {
+ if err := checkXattrName(opts.Name); err != nil {
return err
}
- return i.xattrs.SetXattr(opts)
-}
-
-func (i *inode) removeXattr(creds *auth.Credentials, name string) error {
- if err := i.checkXattrPermissions(creds, name, vfs.MayWrite); err != nil {
+ mode := linux.FileMode(atomic.LoadUint32(&i.mode))
+ kuid := auth.KUID(atomic.LoadUint32(&i.uid))
+ kgid := auth.KGID(atomic.LoadUint32(&i.gid))
+ if err := vfs.GenericCheckPermissions(creds, vfs.MayWrite, mode, kuid, kgid); err != nil {
return err
}
- return i.xattrs.RemoveXattr(name)
+ return i.xattrs.SetXattr(creds, mode, kuid, opts)
}
-func (i *inode) checkXattrPermissions(creds *auth.Credentials, name string, ats vfs.AccessTypes) error {
- // We currently only support extended attributes in the user.* and
- // trusted.* namespaces. See b/148380782.
- if !strings.HasPrefix(name, linux.XATTR_USER_PREFIX) && !strings.HasPrefix(name, linux.XATTR_TRUSTED_PREFIX) {
- return syserror.EOPNOTSUPP
+func (i *inode) removeXattr(creds *auth.Credentials, name string) error {
+ if err := checkXattrName(name); err != nil {
+ return err
}
mode := linux.FileMode(atomic.LoadUint32(&i.mode))
kuid := auth.KUID(atomic.LoadUint32(&i.uid))
kgid := auth.KGID(atomic.LoadUint32(&i.gid))
- if err := vfs.GenericCheckPermissions(creds, ats, mode, kuid, kgid); err != nil {
+ if err := vfs.GenericCheckPermissions(creds, vfs.MayWrite, mode, kuid, kgid); err != nil {
return err
}
- return vfs.CheckXattrPermissions(creds, ats, mode, kuid, name)
+ return i.xattrs.RemoveXattr(creds, mode, kuid, name)
}
// fileDescription is embedded by tmpfs implementations of
@@ -807,7 +826,7 @@ func (fd *fileDescription) StatFS(ctx context.Context) (linux.Statfs, error) {
// ListXattr implements vfs.FileDescriptionImpl.ListXattr.
func (fd *fileDescription) ListXattr(ctx context.Context, size uint64) ([]string, error) {
- return fd.inode().listXattr(size)
+ return fd.inode().listXattr(auth.CredentialsFromContext(ctx), size)
}
// GetXattr implements vfs.FileDescriptionImpl.GetXattr.
diff --git a/pkg/sentry/vfs/memxattr/BUILD b/pkg/sentry/vfs/memxattr/BUILD
index d8c4d27b9..ea82f4987 100644
--- a/pkg/sentry/vfs/memxattr/BUILD
+++ b/pkg/sentry/vfs/memxattr/BUILD
@@ -8,6 +8,7 @@ go_library(
visibility = ["//pkg/sentry:internal"],
deps = [
"//pkg/abi/linux",
+ "//pkg/sentry/kernel/auth",
"//pkg/sentry/vfs",
"//pkg/sync",
"//pkg/syserror",
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 {
generated by cgit v1.2.3 (git 2.39.1) at 2024-12-02 21:16:01 +0000