Check in gVisor.

PiperOrigin-RevId: 194583126
Change-Id: Ica1d8821a90f74e7e745962d71801c598c652463

1 files changed, 140 insertions, 0 deletions

diff --git a/pkg/sentry/syscalls/linux/sys_mount.go b/pkg/sentry/syscalls/linux/sys_mount.go
new file mode 100644
index 000000000..d70b79e4f
--- /dev/null
+++ b/pkg/sentry/syscalls/linux/sys_mount.go
@@ -0,0 +1,140 @@
+// Copyright 2018 Google Inc.
+//
+// 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 linux
+
+import (
+	"gvisor.googlesource.com/gvisor/pkg/abi/linux"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/arch"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/fs"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/kernel"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/usermem"
+	"gvisor.googlesource.com/gvisor/pkg/syserror"
+)
+
+// Mount implements Linux syscall mount(2).
+func Mount(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
+	sourceAddr := args[0].Pointer()
+	targetAddr := args[1].Pointer()
+	typeAddr := args[2].Pointer()
+	flags := args[3].Uint64()
+	dataAddr := args[4].Pointer()
+
+	fsType, err := t.CopyInString(typeAddr, usermem.PageSize)
+	if err != nil {
+		return 0, nil, err
+	}
+
+	sourcePath, _, err := copyInPath(t, sourceAddr, true /* allowEmpty */)
+	if err != nil {
+		return 0, nil, err
+	}
+
+	targetPath, _, err := copyInPath(t, targetAddr, false /* allowEmpty */)
+	if err != nil {
+		return 0, nil, err
+	}
+
+	// In Linux, a full page is always copied in regardless of null
+	// character placement, and the address is passed to each file system.
+	// Most file systems always treat this data as a string, though, and so
+	// do all of the ones we implement.
+	data, err := t.CopyInString(dataAddr, usermem.PageSize)
+	if err != nil {
+		return 0, nil, err
+	}
+
+	// Ignore magic value that was required before Linux 2.4.
+	if flags&linux.MS_MGC_MSK == linux.MS_MGC_VAL {
+		flags = flags &^ linux.MS_MGC_MSK
+	}
+
+	// Must have CAP_SYS_ADMIN in the mount namespace's associated user
+	// namespace.
+	if !t.HasCapabilityIn(linux.CAP_SYS_ADMIN, t.MountNamespace().UserNamespace()) {
+		return 0, nil, syserror.EPERM
+	}
+
+	const unsupportedOps = linux.MS_REMOUNT | linux.MS_BIND |
+		linux.MS_SHARED | linux.MS_PRIVATE | linux.MS_SLAVE |
+		linux.MS_UNBINDABLE | linux.MS_MOVE
+
+	// Silently allow MS_NOSUID, since we don't implement set-id bits
+	// anyway.
+	const unsupportedFlags = linux.MS_NODEV | linux.MS_NOEXEC |
+		linux.MS_NODIRATIME | linux.MS_STRICTATIME
+
+	// Linux just allows passing any flags to mount(2) - it won't fail when
+	// unknown or unsupported flags are passed. Since we don't implement
+	// everything, we fail explicitly on flags that are unimplemented.
+	if flags&(unsupportedOps|unsupportedFlags) != 0 {
+		return 0, nil, syserror.EINVAL
+	}
+
+	rsys, ok := fs.FindFilesystem(fsType)
+	if !ok {
+		return 0, nil, syserror.ENODEV
+	}
+	if !rsys.AllowUserMount() {
+		return 0, nil, syserror.EPERM
+	}
+
+	var superFlags fs.MountSourceFlags
+	if flags&linux.MS_NOATIME == linux.MS_NOATIME {
+		superFlags.NoAtime = true
+	}
+	if flags&linux.MS_RDONLY == linux.MS_RDONLY {
+		superFlags.ReadOnly = true
+	}
+
+	rootInode, err := rsys.Mount(t, sourcePath, superFlags, data)
+	if err != nil {
+		return 0, nil, syserror.EINVAL
+	}
+
+	return 0, nil, fileOpOn(t, linux.AT_FDCWD, targetPath, true /* resolve */, func(root *fs.Dirent, d *fs.Dirent) error {
+		return t.MountNamespace().Mount(t, d, rootInode)
+	})
+}
+
+// Umount2 implements Linux syscall umount2(2).
+func Umount2(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
+	addr := args[0].Pointer()
+	flags := args[1].Int()
+
+	const unsupported = linux.MNT_FORCE | linux.MNT_EXPIRE
+	if flags&unsupported != 0 {
+		return 0, nil, syserror.EINVAL
+	}
+
+	path, _, err := copyInPath(t, addr, false /* allowEmpty */)
+	if err != nil {
+		return 0, nil, err
+	}
+
+	// Must have CAP_SYS_ADMIN in the mount namespace's associated user
+	// namespace.
+	//
+	// Currently, this is always the init task's user namespace.
+	if !t.HasCapabilityIn(linux.CAP_SYS_ADMIN, t.MountNamespace().UserNamespace()) {
+		return 0, nil, syserror.EPERM
+	}
+
+	resolve := flags&linux.UMOUNT_NOFOLLOW != linux.UMOUNT_NOFOLLOW
+	detachOnly := flags&linux.MNT_DETACH == linux.MNT_DETACH
+
+	return 0, nil, fileOpOn(t, linux.AT_FDCWD, path, resolve, func(root *fs.Dirent, d *fs.Dirent) error {
+		return t.MountNamespace().Unmount(t, d, detachOnly)
+	})
+}