1 files changed, 137 insertions, 0 deletions
diff --git a/pkg/sentry/syscalls/linux/vfs2/execve.go b/pkg/sentry/syscalls/linux/vfs2/execve.go
new file mode 100644
index 000000000..066ee0863
--- /dev/null
+++ b/pkg/sentry/syscalls/linux/vfs2/execve.go
@@ -0,0 +1,137 @@
+// 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/fspath"
+	"gvisor.dev/gvisor/pkg/sentry/arch"
+	"gvisor.dev/gvisor/pkg/sentry/fsbridge"
+	"gvisor.dev/gvisor/pkg/sentry/kernel"
+	"gvisor.dev/gvisor/pkg/sentry/loader"
+	slinux "gvisor.dev/gvisor/pkg/sentry/syscalls/linux"
+	"gvisor.dev/gvisor/pkg/sentry/vfs"
+	"gvisor.dev/gvisor/pkg/syserror"
+	"gvisor.dev/gvisor/pkg/usermem"
+)
+
+// Execve implements linux syscall execve(2).
+func Execve(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
+	pathnameAddr := args[0].Pointer()
+	argvAddr := args[1].Pointer()
+	envvAddr := args[2].Pointer()
+	return execveat(t, linux.AT_FDCWD, pathnameAddr, argvAddr, envvAddr, 0 /* flags */)
+}
+
+// Execveat implements linux syscall execveat(2).
+func Execveat(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.SyscallControl, error) {
+	dirfd := args[0].Int()
+	pathnameAddr := args[1].Pointer()
+	argvAddr := args[2].Pointer()
+	envvAddr := args[3].Pointer()
+	flags := args[4].Int()
+	return execveat(t, dirfd, pathnameAddr, argvAddr, envvAddr, flags)
+}
+
+func execveat(t *kernel.Task, dirfd int32, pathnameAddr, argvAddr, envvAddr usermem.Addr, flags int32) (uintptr, *kernel.SyscallControl, error) {
+	if flags&^(linux.AT_EMPTY_PATH|linux.AT_SYMLINK_NOFOLLOW) != 0 {
+		return 0, nil, syserror.EINVAL
+	}
+
+	pathname, err := t.CopyInString(pathnameAddr, linux.PATH_MAX)
+	if err != nil {
+		return 0, nil, err
+	}
+	var argv, envv []string
+	if argvAddr != 0 {
+		var err error
+		argv, err = t.CopyInVector(argvAddr, slinux.ExecMaxElemSize, slinux.ExecMaxTotalSize)
+		if err != nil {
+			return 0, nil, err
+		}
+	}
+	if envvAddr != 0 {
+		var err error
+		envv, err = t.CopyInVector(envvAddr, slinux.ExecMaxElemSize, slinux.ExecMaxTotalSize)
+		if err != nil {
+			return 0, nil, err
+		}
+	}
+
+	root := t.FSContext().RootDirectoryVFS2()
+	defer root.DecRef(t)
+	var executable fsbridge.File
+	closeOnExec := false
+	if path := fspath.Parse(pathname); dirfd != linux.AT_FDCWD && !path.Absolute {
+		// We must open the executable ourselves since dirfd is used as the
+		// starting point while resolving path, but the task working directory
+		// is used as the starting point while resolving interpreters (Linux:
+		// fs/binfmt_script.c:load_script() => fs/exec.c:open_exec() =>
+		// do_open_execat(fd=AT_FDCWD)), and the loader package is currently
+		// incapable of handling this correctly.
+		if !path.HasComponents() && flags&linux.AT_EMPTY_PATH == 0 {
+			return 0, nil, syserror.ENOENT
+		}
+		dirfile, dirfileFlags := t.FDTable().GetVFS2(dirfd)
+		if dirfile == nil {
+			return 0, nil, syserror.EBADF
+		}
+		start := dirfile.VirtualDentry()
+		start.IncRef()
+		dirfile.DecRef(t)
+		closeOnExec = dirfileFlags.CloseOnExec
+		file, err := t.Kernel().VFS().OpenAt(t, t.Credentials(), &vfs.PathOperation{
+			Root:               root,
+			Start:              start,
+			Path:               path,
+			FollowFinalSymlink: flags&linux.AT_SYMLINK_NOFOLLOW == 0,
+		}, &vfs.OpenOptions{
+			Flags:    linux.O_RDONLY,
+			FileExec: true,
+		})
+		start.DecRef(t)
+		if err != nil {
+			return 0, nil, err
+		}
+		defer file.DecRef(t)
+		executable = fsbridge.NewVFSFile(file)
+	}
+
+	// Load the new TaskContext.
+	mntns := t.MountNamespaceVFS2() // FIXME(jamieliu): useless refcount change
+	defer mntns.DecRef(t)
+	wd := t.FSContext().WorkingDirectoryVFS2()
+	defer wd.DecRef(t)
+	remainingTraversals := uint(linux.MaxSymlinkTraversals)
+	loadArgs := loader.LoadArgs{
+		Opener:              fsbridge.NewVFSLookup(mntns, root, wd),
+		RemainingTraversals: &remainingTraversals,
+		ResolveFinal:        flags&linux.AT_SYMLINK_NOFOLLOW == 0,
+		Filename:            pathname,
+		File:                executable,
+		CloseOnExec:         closeOnExec,
+		Argv:                argv,
+		Envv:                envv,
+		Features:            t.Arch().FeatureSet(),
+	}
+
+	tc, se := t.Kernel().LoadTaskImage(t, loadArgs)
+	if se != nil {
+		return 0, nil, se.ToError()
+	}
+
+	ctrl, err := t.Execve(tc)
+	return 0, ctrl, err
+}