Port memfd_create to vfs2 and finish implementation of file seals.

Closes #2612.

PiperOrigin-RevId: 311548074

4 files changed, 76 insertions, 1 deletions

diff --git a/pkg/sentry/syscalls/linux/vfs2/BUILD b/pkg/sentry/syscalls/linux/vfs2/BUILD
index c32f942fb..f882ef840 100644
--- a/pkg/sentry/syscalls/linux/vfs2/BUILD
+++ b/pkg/sentry/syscalls/linux/vfs2/BUILD
@@ -13,6 +13,7 @@ go_library(
         "fscontext.go",
         "getdents.go",
         "ioctl.go",
+        "memfd.go",
         "mmap.go",
         "path.go",
         "pipe.go",
@@ -43,6 +44,7 @@ go_library(
         "//pkg/sentry/fsimpl/pipefs",
         "//pkg/sentry/fsimpl/signalfd",
         "//pkg/sentry/fsimpl/timerfd",
+        "//pkg/sentry/fsimpl/tmpfs",
         "//pkg/sentry/kernel",
         "//pkg/sentry/kernel/auth",
         "//pkg/sentry/kernel/pipe",
diff --git a/pkg/sentry/syscalls/linux/vfs2/fd.go b/pkg/sentry/syscalls/linux/vfs2/fd.go
index 8181d80f4..ca0f7fd1e 100644
--- a/pkg/sentry/syscalls/linux/vfs2/fd.go
+++ b/pkg/sentry/syscalls/linux/vfs2/fd.go
@@ -17,6 +17,7 @@ package vfs2
 import (
 	"gvisor.dev/gvisor/pkg/abi/linux"
 	"gvisor.dev/gvisor/pkg/sentry/arch"
+	"gvisor.dev/gvisor/pkg/sentry/fsimpl/tmpfs"
 	"gvisor.dev/gvisor/pkg/sentry/kernel"
 	"gvisor.dev/gvisor/pkg/sentry/kernel/pipe"
 	slinux "gvisor.dev/gvisor/pkg/sentry/syscalls/linux"
@@ -157,6 +158,15 @@ func Fcntl(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Syscall
 			return 0, nil, syserror.EBADF
 		}
 		return uintptr(pipefile.PipeSize()), nil, nil
+	case linux.F_GET_SEALS:
+		val, err := tmpfs.GetSeals(file)
+		return uintptr(val), nil, err
+	case linux.F_ADD_SEALS:
+		if !file.IsWritable() {
+			return 0, nil, syserror.EPERM
+		}
+		err := tmpfs.AddSeals(file, args[2].Uint())
+		return 0, nil, err
 	default:
 		// TODO(gvisor.dev/issue/1623): Everything else is not yet supported.
 		return 0, nil, syserror.EINVAL
diff --git a/pkg/sentry/syscalls/linux/vfs2/memfd.go b/pkg/sentry/syscalls/linux/vfs2/memfd.go
new file mode 100644
index 000000000..bbe248d17
--- /dev/null
+++ b/pkg/sentry/syscalls/linux/vfs2/memfd.go
@@ -0,0 +1,63 @@
+// Copyright 2020 The gVisor Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package vfs2
+
+import (
+	"gvisor.dev/gvisor/pkg/abi/linux"
+	"gvisor.dev/gvisor/pkg/sentry/arch"
+	"gvisor.dev/gvisor/pkg/sentry/fsimpl/tmpfs"
+	"gvisor.dev/gvisor/pkg/sentry/kernel"
+	"gvisor.dev/gvisor/pkg/syserror"
+)
+
+const (
+	memfdPrefix     = "memfd:"
+	memfdMaxNameLen = linux.NAME_MAX - len(memfdPrefix)
+	memfdAllFlags   = uint32(linux.MFD_CLOEXEC | linux.MFD_ALLOW_SEALING)
+)
+
+// MemfdCreate implements the linux syscall memfd_create(2).
+func MemfdCreate(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
+	addr := args[0].Pointer()
+	flags := args[1].Uint()
+
+	if flags&^memfdAllFlags != 0 {
+		// Unknown bits in flags.
+		return 0, nil, syserror.EINVAL
+	}
+
+	allowSeals := flags&linux.MFD_ALLOW_SEALING != 0
+	cloExec := flags&linux.MFD_CLOEXEC != 0
+
+	name, err := t.CopyInString(addr, memfdMaxNameLen)
+	if err != nil {
+		return 0, nil, err
+	}
+
+	shmMount := t.Kernel().ShmMount()
+	file, err := tmpfs.NewMemfd(shmMount, t.Credentials(), allowSeals, memfdPrefix+name)
+	if err != nil {
+		return 0, nil, err
+	}
+
+	fd, err := t.NewFDFromVFS2(0, file, kernel.FDFlags{
+		CloseOnExec: cloExec,
+	})
+	if err != nil {
+		return 0, nil, err
+	}
+
+	return uintptr(fd), nil, nil
+}
diff --git a/pkg/sentry/syscalls/linux/vfs2/vfs2.go b/pkg/sentry/syscalls/linux/vfs2/vfs2.go
index 9c04677f1..ec8da7f06 100644
--- a/pkg/sentry/syscalls/linux/vfs2/vfs2.go
+++ b/pkg/sentry/syscalls/linux/vfs2/vfs2.go
@@ -158,7 +158,7 @@ func Override() {
 	s.Table[306] = syscalls.Supported("syncfs", Syncfs)
 	s.Table[307] = syscalls.Supported("sendmmsg", SendMMsg)
 	s.Table[316] = syscalls.Supported("renameat2", Renameat2)
-	delete(s.Table, 319) // memfd_create
+	s.Table[319] = syscalls.Supported("memfd_create", MemfdCreate)
 	s.Table[322] = syscalls.Supported("execveat", Execveat)
 	s.Table[327] = syscalls.Supported("preadv2", Preadv2)
 	s.Table[328] = syscalls.Supported("pwritev2", Pwritev2)